Published 1997

5 Sunflower Insects

LAURENCE D. CHARLET USDA-ARS Northern Crop Science Laboratory Fargo, North Dakota

GARY J. BREWER North Dakota State University Fargo, North Dakota

BERNARD A. FRANZMANN Queensland Department ofPrimary Industries Toowoomba 4350 Australia

A diverse assemblage of insect species attack sunflower (Helianthus annuus L.) worldwide (Rajamohan, 1976; Rogers, 1992). Since sunflower is native to North America, a large pest complex has evolved on wild sunflower and has moved from wild ancestors to commercial cultivars. In other countries and to a lesser extent in North America, some insects have adapted to utilize sunflower as an alternative host. Many of these insects develop or increase in number on adjacent or earlier-planted crops and then after senescence move to sunflower. The successful management of insect pests depends on correctly identify• ing the pest, understanding the pest's biology, field sampling of pest densities, and selecting the appropriate control methods. The use of integrated pest man• agement assures that control decisions will be based on economics and achieved with minimal disruption to the environment, the least possible harm to nontarget organisms, and reduced probability that secondary or minor pests will likely become a problem. The integrated pest management philosophy will assure that the most effective control strategies are management techniques that combine resistant cultivars, cultural control, biological control, and the application of insecticides only when pest populations have reached economic injury levels. Insecticides approved for usage on specific insects are constantly changing based on the registration of new products or loss of current registration, therefore the local county agent, crop consultant, or state extension service should be contact• ed for current recommendations. The discussion of insects associated with sun• flower that follows is organized by the continent or region in which they occur and by the part ofthe plant attacked (see insert with color plates).

Copyright © 1997. American Society of Agronomy. Crop Science Society of America, Soil Science Society of America, 677 S. Segoe Rd., Madison, WI 53711, USA. Sunflower Technology and Produc• tion, Agronomy Monograph no. 35 .

183 184 CHARLET ET AL.

INSECT PESTS OF THE UNITED STATES, CANADA, AND MEXICO

Sunflower is utilized by a wide array of insect species, both as a food plant and as a source of pollen and nectar. Over 150 phytophagous insect species have been reported from cultivated and native species of sunflower in North America (Hilgendorf & Goeden, 1981; Rogers, 1988b). Sunflower is the only row crop in North America that coexists with its native congeners. This unique relationship has enhanced development of insect problems by providing monocultures of host plants where only isolated hosts were once available. A number of insect species have adapted to cultivated sunflower and have become consistent economic pests (Charlet et aI., 1987).

STEM AND ROOT FEEDING SPECIES

Cutworms [Lepidoptera: Noctuidae]

Cutwonns are perennial pests of sunflower occurring in isolated outbreaks. In the upper Great Plains of North America, four species are common. These are the dark-sided cutwonn [Euxoa messoria (Harris)], the red-backed cutwonn [E. ochrogaster (Guenee)], the pale western cutwonn (Agrotis orthogonia Morrison), and the dingy cutwonn (Feltia ducens Walker). Other cutwonn species attacking sunflower vary by region (Westdal, 1975).

Description Dark-Sided Cutworm. The adult has forewings that are usually light, powdery, and grayish-brown with indistinct markings. Larvae are pale-brown dorsally, white on the ventral areas, and with indistinct stripes on the sides. At maturity, larvae are 25 to 32 mm in length. Red-Backed Cutworm. Forewings of the adult are reddish-brown with characteristic bean-shaped markings. The larvae are dull-gray to brown with soft fleshy bodies and are from 25 to 32 mm in length when grown. Larvae are char• acterized by two dull-reddish stripes along the dorsal side. Pale Western Cutworm. Forewings on the adult are tan and mottled with light-colored primary wing veins. Hindwings are white, darkening distally. Larvae are grayish in color without spots or stripes, but the body has fine, flat granules. Dingy Cutworm. Adults have forewings with bean-shaped markings sim• ilar to those found on the red-backed cutworm. The hind wings of males are whitish with a broad, dark margin along the outside while those o( females are unifonn dark gray in color. Larvae are a dull, dingy-brown color with a broad, dull-gray dorsal stripe, which is separated into triangular-shaped areas on each segment. A narrow, dark stripe is on each margin of the central stripe (Capinera & Schaefer, 1983; McBride et aI., 1985, 1994; Metcalf & Metcalf, 1993). SUNFLOWER INSECTS 185

Life History The dark-sided and red-backed cutworms have similar life histories. Larvae of these species emerge in May and early June and develop until about the end of June. Pupation lasts about 3 wk and takes place in the soil in earthen cells near the soil surface. Eggs are oviposited in the soil in late July and early August and remain dormant until the following spring. There is one generation per year. The pale western cutworm feeds underground and usually ceases feeding by late June. Eggs are laid singly or in small groups on the soil and hatch on warm winter days or in early spring. There is a single generation per year. The dingy cutworm is a northern species. They emerge as adults in August and are active until mid-October. Eggs are deposited and hatch in the fall. Dingy larvae develop to the second or third instar before overwintering in the soil. Pupation occurs in the spring to early summer. There is one generation per year (McBride et al., 1985, 1994; Metcalf & Metcalf, 1993).

Damage Cutworms damage sunflower by cutting the stem of the plant from 2 to 5 mm above or below the soil line, although occasionally, damage may occur at greater distances from the soil line. Sometimes, larvae, especially the dark-sided, climb the plant to feed on foliage. Larvae are most active at night and hide in the soil during the day. Wilted and dead plants are evidence of cutworm damage. Severed plants wither and may blow away leaving distinct bare patches in the sunflower field. Cutworms have a wide host range and infest most row crops. In sunflower, a gap of 10 to 12 plants in a row is necessary before an economic loss is seen (McBride et al., 1985, 1994).

Management Strategies Sampling should begin as soon as sunflower plants emerge and fields should be checked twice weekly until about mid-June. The soil around damaged plants should be inspected for cutworm larvae. Species that feed above the soil line can be controlled with the use of poison-bran baits. For other species, insec• ticides have to be incorporated into the soil. Several insecticides are registered for cutworm control in the USA and Canada. Cutworms are parasitized by a variety of tachinid and hymenopteran parasitoids and insect predators consume a signif• icant number of cutworm larvae. Disease and birds also limit cutworm damage (McBride et al., 1985, 1994; Metcalf & Metcalf, 1993).

Sunflower Bud Moth, Suleima helianthana (Riley) [Lepidoptera: Tortricidae]

The only lepidopterous species of potential economic concern as a stem pest is the sunflower bud moth. The moth is found on sunflower from Mexico to the central USA, occurring in all the sunflower growing areas (Pedraza-Martinez, 1990; Rogers, 1979). 186 CHARLET ET AL.

Description Moths have gray to brown forewings with two dark bands and a light patch on the back half of the wing tip (Color Plate 1). The first band runs through the middle of the wing. The second band is located near the wingtip. The wingspan is about 17 mm. Eggs are ovoid and translucent-white in color. Sculpturing on the egg surface gives it a wrinkled appearance. Larvae have smooth, cream-colored bodies with yellow-brown head capsules and are about 15 mm in length at matu• rity. There are five larval instars. Pupae are found in feeding tunnels near the lar• val entrance hole into the stem (Ehart, 1974).

Life History In the Red River Valley of North Dakota and Minnesota, first-generation adults emerge from late May to mid-June and deposit single eggs on the terminal portion of the plant (Ehart, 1974). Larvae tunnel into the stalk, leaf petiole, or receptacle to feed on the pith. Larval tunnels are usually less than 3 cm in length (Rogers, 1979). At maturity, larvae return to the entrance hole to pupate. Entrance holes are characterized by a protuding, black, sticky frass (Color Plate 2). They can be found in the stalk, leaf petiole, or less commonly, the bud. Second-generation adults appear in late July, oviposit on the sunflower bud or stalk, and are active until mid-August. Larvae of the second generation are more likely to feed in the receptacle of the capitula than the first generation. Larvae plug the entrance hole with frass and other material and burrow into undisturbed pith to overwinter (Ehart, 1974). In Texas, infestations can occur in early May. There are two generations per season in North Dakota and northern Texas and possibly three generations per season in south-central Texas (Phillips, 1972). Host species include wild and commercial H. annuus and 16 other species of Helianthus (Rogers, 1979).

Damage Infestations are sporadic but can be heavy at times. Although larval feed• ing sometimes produces malformed stalks, leaf petioles, and capitula, tunneling in stalks does not normally interfere with stem development. Economic damage is usually restricted to those plants in which infestation occurred in terminals of very small plants or in small capitula. Larvae do not feed on seeds but consume the pithy part of the head (Ehart, 1974; Rogers, 1979). Under dry conditions when plants are stressed, infestations may result in severe yield loss (Pedraza-Martinez, 1990).

Management Strategies Although plant injury symptoms are quite evident in cultivated fields, loss• es are usually not sufficient to necessitate the use of control measures for the sun• flower bud moth. Late planting reduces infestation by first-generation larvae but increases the probability of a second-generation infestation. Plant resistance has not been detected (Ehart, 1974). Larvae are attacked by the parasitic ichneumonid SUNFLOWER INSECTS 187 wasps, Macrocentrus sp., Glypta sp., and Temelucha sp. and a predaceous fly larva of the family Stratiomyidae (Brassard, 1976).

Sunflower Stem Weevil, Cylindrocopturus adspersus (LeConte) [Coleoptera: Curculionidae]

The sunflower stem weevil was first described as a pest of sunflower by Newton (1921) in Colorado. The stem weevil has become an economic pest of cultivated sunflower in both the northern and southern Great Plains of the USA (Phillips et al., 1973; Schulz, 1978; Rogers & Jones, 1979). It also has been found in sunflower stalks in Saskatchewan (Arthur & Mason, 1990). The weevil also is recorded from different species of ragweed (Ambrosia spp.) (Goeden & Ricker, 1975, 1976) in addition to native Helianthus species (Charlet, 1983b; Charlet et aI., 1992). The larval stage feeds, develops, and overwinters in the sunflower stem (Rogers & Serda, 1982; Charlet, 1987). Weakened stalks of heavily infest• ed plants may lodge prior to harvest (Rogers & Jones, 1979). The weevil also has been implicated in the transmission of fungal pathogens (Gaudet & Schulz, 1981; Yang et al., 1983; Charlet & Gulya, 1984).

Description Adults are 4 to 5 mm long and grayish-brown with varing-shaped white spots on the elytron (wing covers) and thorax (Color Plate 3). The snout, eyes, and antennae are black. The larvae are 5 to 6 mm long at maturity. They are creamy-white with a small, brown head capsule and are legless. They are nor• mally in a curled or C-shaped position within the sunflower stalk (Casals-Bustos, 1976; McBride et al., 1990).

Life History Adults emerge from overwintered stalks and root crowns in early to mid• April in the southern Plains and mid- to late June in the northern Plains. Females deposit eggs under the epidermis at the base of sunflower stalks (Rogers & Serda, 1982; Charlet, 1987). Adults feed on stem and leaf tissue. Adults are present in the fields in the northern Plains until late August (Charlet, 1987). In North Dakota, 50% of eggs are deposited by mid-July (Charlet, 1983c). Under labora• tory conditions, females oviposited 0.5 to 5 eggs per day for a total production of 24 to 195 eggs, depending on temperature. Females survived up to 75 d when held at 20 or 23°C (Barker, 1987). Early instar larvae feed in the vascular tissue and, as the larvae mature, tunnel into the pith. Larvae descend to the lower por• tion of the stalk or root crown by late August and excavate overwintering cham• bers by chewing cavities into the stem cortex (Rogers & Serda, 1982; Charlet 1983a). There is only one generation per year (Charlet, 1987).

Damage

Feeding by adults on the stem and leaf tissue causes minor damage to the plant. If the larval population in a plant is high, the stem, weakened by tunneling, 188 CHARLET ET AL. pith destruction, or overwintering chambers, will break causing a loss of the entire capitula prior to harvest (Color Plate 4). In North Dakota, a mean infesta• tion of 38 larvae resulted in 28% lodging (Charlet et aI., 1985). Stalk breakage due to the sunflower stem weevil is most severe during drought stress or when high winds occur as plants are drying prior to harvest (Charlet, 1991b). Populations of over 80 larvae/stalk in irrigated sunflower in the southern Plains were required before there was yield loss due to larval feeding (Rogers & Jones, 1979). The sunflower stem weevil also has been implicated in the epidemiology of sunflower pathogens, such as Phoma black stem (Phoma macdonaldii Boerma), that contribute to the premature ripening syndrome in the northern Plains and may predispose plants to infection by Macrophomina phaseolina (Tassi) Goid, the causative agent of charcoal stem rot in sunflower in the south• ern Plains (Gaudet & Schulz, 1981; Yang et aI., 1983; Charlet & Gulya, 1984).

Management Strategies The use of both foliar and systemically applied insecticides has been shown to be effective in reducing larval populations and percentage of stalks lodged (Charlet & Oseto, 1983; Rogers et aI., 1983; Charlet et aI., 1985). However, chemically reduced larval densities have not consistently resulted in greater seed yields. In the northern Plains, treatment must be initiated from late June to early July before appreciable egg laying has occurred to reduce larval numbers in the stalk (Charlet, 1987). Delayed planting was effective in both the northern and southern Plains as a management tool in lowering larval densities in sunflower stalks (Rogers & Jones, 1979; Oseto et aI., 1982; Rogers et aI., 1983; Charlet & Brewer, 1994). Tillage was ineffective in increasing mortality of overwintering larvae due to protection of the larvae within the woody portion of stalks, but bur• ial of stalks reduced adult emergence (Rogers et aI., 1983; Charlet, 1994a). Charlet (1989) noted that overwintering survival of the larvae varied with micro• habitat and that the mortality of larvae was not increased unless exposed in the soil. Greenhouse and field experiments have shown resistance to feeding, ovipo• sition, and larval development in many native species of sunflower (Rogers & Seiler, 1985). Barker (1991) indicated that although there was reduced feeding by adults on some native sunflower species, it was not associated with high trichome density. A number of species of parasitic wasps attack sunflower stem weevillar• vae. Anaphes conotracheli Girault (Hymenoptera: Mymaridae) was reared from eggs of the weevil (Charlet & Balsbaugh, 1984). Larvae are attacked by the fol• lowing Hymenoptera in the northern Great Plains: Nealiolus curculionis (Fitch) (Braconidae), Tetrastichus ainsliei Gahan (Eulophidae), and Mesopolobus sp. (Pteromalidae) (Charlet, 1983d). Rogers (1980) reported two species from the weevil in Texas: N curculionis and Neocatolaccus tylodermae (Ashmead) (Pteromalidae). Rhaconotus cressoni Muesebeck and Walkley (Braconidae), Eupelmus cushmani (Crawford), E. cyaniceps (Ashmead) (Eupelmidae), and Zatropis incertus (Ashmead) (Pteromalidae) also have been reported to attack lar• vae of the weevil (Casals-Bustos, 1976; Krombein et aI., 1979). Nealiolus cur• culionis represented over 96% of the parasitoids attacking the weevil from 1980 SUNFLOVVERINSECTS 189 to 1991 in North Dakota and is a consistent mortality factor even when weevil densities are low (Charlet, 1994b). The impact of pesticides on natural enemies must be considered in developing managment programs, since insecticides that are toxic to the weevil also reduced parasitism (Charlet & Oseto, 1983).

Black Sunflower Stem Weevil, Apion occidentale Fall [Coleoptera: Curculionidae]

Of the various weevil species infesting sunflower, the first to emerge from overwintering is the black sunflower stem weevil. This weevil has been reported from North Dakota, Minnesota, and Texas (Gaudet & Schulz, 1981; Rogers, 1988b).

Description Adults are shiny-black and only 2.5 mm long from the tip of the snout to the tip of the abdomen (Color Plate 5). The snout is very narrow and protrudes forward from the head, which is small in relation to the rather large, almost glo• bose body. The larvae are similar in appearance to those of the sunflower stem weevil, but are smaller (2.5-3 mm) in length at maturity and more yellow in color while the posterior is more pointed (McBride et al., 1990).

Life History Adults overwinter in soil or plant residue, and emerge from late May to early June. Eggs are deposited under the epidermis in leaf petioles or stems near axils. Adults feed from early spring to late July on leaf and stem tissue. Feeding by larvae takes place in vascular and pith tissue of both stem and petiole. Larvae pupate within the feeding tunnels and adults emerge in August. Adults emerging in late summer feed on stem and leaf tissue and congregate under the bracts sur• rounding the maturing sunflower capitula. Adults move into the soil from late August to September to pass the winter (Gaudet & Schulz, 1981).

Damage Feeding damage is seldom significant, but the weevil has been associated with the transmission of the pathogen Phoma macdonaldii Boerma, the causal agent of Phoma black stem (Gaudet & Schulz, 1981, 1984).

Management Strategies The weevil, although numerous in cultivated sunflower fields, has not been considered an economically important pest due to the lack of significant mechan• ical or physiological damage (Gaudet & Schulz, 1981). Therefore, control mea• sures have not been developed. The evidence that it can transmit fungal pathogens may someday necessitate research into control methods. 190 CHARLET ET AL.

Sunflower Root Weevil, Baris strenua (LeConte) [Coleoptera: Curculionidae)

The sunflower root weevil occurs from Illinois to California and Montana to Guatemala (Casals-Bustos, 1976). In North Dakota, it has been reported from H. annuus, H. petio/aris Nuttall, and H. maximiliani Torrey and Gray as well as other members of the Compositae (Casals-Bustos, 1976). In other locations, the sunflower root weevil has been reported from H. grosseserratus Martens and H. paradoxus Heiser (Tuttle, 1952; Rogers, 1988b). Damage has only been reported from isolated fields in southeastern North Dakota (Schulz, 1978).

Description The adults are robust with a somewhat oval-shaped body and dull-black color. They are 4 to 6 mm in length and have a short rostrum (Color Plate 6). Eggs are 1 mm, ovoid, and creamy-white. The eggs tum dark-brown prior to hatching. Larvae are similar in appearance to sunflower stem weevil larvae. They have a white body, a C-shaped appearance, and the fourth instar is 6 mm in length. The pupa is yellowish-white and 5 mm long (Casals-Bustos, 1976).

Life History Adults of the sunflower root weevil emerge in late June and initially feed on sunflower foliage. Adults move to the base of the plant about 1 wk after emer• gence and feed on stem tissue causing the plants to produce callus at the feeding site. Eggs are inserted singly in the callus tissue and larvae feed on the epidermis and cortical cells of the root. There are four larval instars. Larvae overwinter in soil-coated cocoons formed at the base of the plant and have been found as deep as 45 cm below the soil surface (Casals-Bustos, 1976). There is only one gener• ation per year.

Damage The destruction of root tissue causes plants to wilt and lodge if infestation is severe (Color Plate 7).

Management Strategies The root weevil has been only a minor pest in isolated locations, so no con• trol measures have been developed (Schulz, 1978). Casals-Bustos (1976) report• ed that fall moldboard plowing reduced overwintering larval populations of the sunflower root weevil in North Dakota. Larvae are parasitized by the braconid wasp, Bracon baridii Marsh, in North Dakota (Casals-Bustos, 1976).

Sunflower Maggot, Strauzia iongipennis (Wiedemann) [Diptera: Tephritidae)

The univoltine sunflower maggot is the only tephritid species found in the stalk of cultivated sunflower. It is a widespread species, occurring in most areas SUNFLOWER INSECTS 191 in the USA and many of the Canadian provinces (Brink, 1923). This pest also has been recovered from the native sunflower species, H. annuus, H. maximiliani, and H. tuberosus L. (Westdal & Barrett, 1960; Charlet et aI., 1992).

Description The showy yellow adult has a wing span of about 13 mm with a body about 8 mm long. The eyes are bright green and the wings bear broad dark bands that form a fairly distinct F- pattern near the wing tip (Color Plate 8). Eggs are 1 mm long, white and elongate. The larvae are yellow-white, tapered from anterior to posterior, and approximately 9 mm long and 2.5 mm wide at maturity. The larvae develop through three instars in approximately 6 wk (Westdal & Barrett, 1960).

Life History Adults emerge in mid-June, although adult flies have been noted in shel• terbelts or field margins as early as late May. The adult fly is very active during the day and are present in fields until late July. Eggs are deposited singly in stem tissue near the apical meristem and larvae feed in the stalk pith creating large tun• nels (Color Plate 9). The maggots, when fully developed, emerge from the stalk beginning in mid-August and overwinter as pupae in the soil at the base of the sunflower plant (Westdal & Barrett, 1960).

Damage Economic loss due to larval feeding has not been documented for this insect in recent years, even though larvae are commonly found in up to 100% of sun• flower stalks (Schulz, 1978). Feeding is confined to the pith, which acts as a sup• porting structure, and is not critical to plant nutrition. Secondary fungal infections also are associated with tunneling by the larvae within the stalk. Stalks are not weakened and seed yield is not reduced even with severe pith destruction (Westdal & Barrett, 1962).

Management Strategies Chemical treatment was effective in preventing pith damage to sunflower when applied after oviposition by the sunflower maggot female fly. Larval infes• tation also has been reduced 30 to 90% with applications of insecticides (Allen et aI., 1954; Schulz, 1978). Pupae are attacked by a braconid wasp, Psi/us sp. (Westdal & Barrett, 1960). The lack of evidence for seed yield reduction from maggot feeding indicates that control measures are seldom necessary (Schulz, 1978).

Long-horned Sunflower Stem Girdler, Dectes texan us LeConte [Coleoptera: Cerambycidae]

The long-homed sunflower stem girdler only recently has been detected causing economic damage to sunflower growing in North Dakota and South 192 CHARLET ET AL.

Dakota (Charlet et ai., 1987). However, it is an important girdling pest of culti• vated sunflower in the southern Plains (Rogers, 1977b). The cerambycid also is present in native sunflower species, ragweed (Ambrosia artemisiifolia L.), and cocklebur (Xanthium strumarium L.) (Charlet, 1983b; Rogers, 1985). This pest also has been reported from cultivated sunflower in Florida (Genung & Green, 1983). It has been an economically important pest of soybean [Glycine max (L.) Merr.], in the southeastern USA (Hatchett et ai., 1975; Campbell & Van Duyn, 1977).

Description The adult is pale-gray, 6 to 11 mm in length with long antennae (Color Plate 10). Eggs are about l.9 mm long, elongate, and tum dark-yellow prior to eclo• sion. Mature larvae are yellowish and 7 to 13 mm in length. Larvae bear fleshy protuberances on the first seven abdominal segments (Hatchett et aI., 1975).

Life History Adults appear in late June and early July and deposit eggs in leaf petioles. Emergence continues through August with 50% emerged by 15 July in Texas (Rogers, 1985). Larvae tunnel and feed in the petioles and stem pith and finally move to the base of the plant to overwinter (Rogers, 1977b, 1985). In late sum• mer, the mature larvae internally girdle the lower stalk or root crown, move below the girdle, and pack frass into the tunnels. Stalks often break at the point of girdling, leaving the larva in its frass-packed tunnel protected during the winter. The larvae are cannibalistic, thus stalks usually harbor only a single larva even though several may have originally hatched in a stalk (Charlet et aI., 1987). There is one generation per year.

Damage Plant damage due to adult feeding appears to be insignificant, since the scars do not penetrate the cortex nor encircle the stalk (Rogers, 1977b). Larval feeding is apparent when stalks lodge at the point of the girdle, about 7 to 9 cm above the soil surface.

Management Strategies In the southern Plains, adjustments in planting dates and fall or winter tillage reduced infestations of sunflower by this cerambycid pest. Perennial sun• flower species are resistant to stalk infestation (Rogers, 1985), indicating the pos• sibility of breeding cultivars resistant to the long-homed sunflower stem girdler. Systemic chemical treatments on soybean and sunflower are ineffective against larvae and were determined to be impractical against adults because of the extended emergence period (Rogers, 1985). Hatchett et ai. (1975) reported seven species of Hymenoptera representing the families Braconidae, Pteromalidae, and Ichneumonidae reared from larvae collected from giant ragweed (A. trifida L). SUNFLOWER INSECTS 193

Carrot Beetle, Ligyrus gibbosus (DeGreer) [Coleoptera: Scarabaeidae]

The carrot beetle has a wide host range and occurs throughout the USA, southern Canada, and northern Mexico (Rogers, 1974). Twenty-four species of noncultivated plants have been noted as hosts for this beetle. The preferred hosts include H. annuus, H. petiolaris, carelessweed (Amaranthus palmeri Wats.), horse weed (Conyza canadensis Cronquist), sawleaf daisy (Prionopsis ciliata Nutt.), silverleaf nightshade (Solanum elaeagnifolium Cav.), and white rosinweed (Silphium albiforum Gray) (Rogers, 1974). Aslam and Wilde (l991a) recorded damage from the carrot beetle at two locations in Kansas. However, it has been a serious pest of sunflower only in the High and Rolling Plains of Texas and adjoin• ing areas of Oklahoma (Bottrell et aI., 1973; Schulz, 1978).

Description Adults are large, 10 to 17 mm long by 6 to 11 mm wide, oblong-oval, red• dish-brown scarab beetles (Color Plate 11). They are frequently mistaken for June bugs or May beetles. Eggs are white, smooth, shining and 2.5 mm in length at maturity. Newly emerged larvae or grubs are white except for the brown-colored mandibles. Within a few hours, the head capsule darkens and turns brown. Mature larvae are 31 mm long and 9 mm wide with a bluish coloration. Larvae crawl on their sides or legs and lie coiled on their sides when disturbed. The pupal stage is 15 mm long and 9 mm wide and turns from creamy-white to light-brown after molting (Hayes, 1917).

Life History The carrot beetle is univoltine with mass emergence of overwintering adults from the soil in early April. Mating takes place and females begin ovipo• sition by early May. Overwintered adults may survive until early July. The adult burrows into the soil around the plant roots at night. They hide during the day in the soil or under objects, but at night are attracted to lights. Preferred breeding sites are sandy or sandy loam soils (Rogers, 1974). Eggs are deposited at the base of plants in soil high in organic matter. Eggs hatch in about 11 d (Hayes, 1917). The larvae or grubs are detritus feeders and do not occur in sunflower fields (Rogers, 1974). However, they have been reported feeding on roots of maize (Zea mays L.), oat (Avena sativa L.), and wheat (Triticum aestivum L. emend. TheiL). The development of larval and prepupal stages requires approximately 59 d and the pupal stage 19 d (Hayes, 1917). The progeny of the overwintered adults begin emerging toward the end of July. Adults overwinter in the soil wherever they are located when winter arrives (Rogers, 1974).

Damage Damage occurs as a result of adult pruning of lateral roots and feeding on the taproot, which causes sudden wilting and death of the sunflower plant (Bottrell et aI., 1973). Population densities of two or more adults per plant can destroy enough root tissue to interfere with plant uptake of nutrients and water (Brigham et aI., 1974). 194 CHARLET ET AL.

Management Strategies Application of insecticides has been ineffective in preventing economic damage to roots from adult feeding (Brigham et aI., 1974). Larvae are reported to be cannibalistic (Hayes, 1917). Adults are attacked by five species of parasitic flies in the family Sarcophagidae and pathogens (bacteria and fungi). Adults also are destroyed by a number of vertebrate predators including several species of birds, toads (Bufo spp.), skunks (Mustelidae), opossums (Didelphis virginiana Kerr), coyotes (Canis latrans Say), and raccoons [Procyon lotor (L.)]. Larval mortality is due to attack by predaceous carabid beetles and pathogens (Hayes, 1917; Rogers & Howell, 1973; Rogers, 1974). Studies have shown resistance in about one-half the native species of Helianthus with perennials less susceptible than annuals (Rogers & Thompson, 1978a; Rogers et aI., 1980).

FOLIAGE FEEDING SPECIES

Grasshoppers [Orthoptera: Acrididae]

Several species of grasshoppers are occasional pests of sunflower. In the central Plains, the most important grasshoppers are: differential grasshopper, Melanoplus difJerentialis (Thomas); migratory grasshopper, M sanguinipes (Fabricius); two striped grasshopper, M bivittatus (Say); redlegged grasshopper, M femurrubrum (DeGeer); and the clearwinged grasshopper, Camnula pellucida (Scudder) (Schulz, 1978; McBride et aI., 1987).

Description Differential Grasshopper. The differential grasshopper is brown or olive green in color with a yellowish underside. There are prominent, black V-shaped markings or chevrons on the outside of the hind leg. Differential grasshoppers are large, adult males being 2.9 to 4.1 cm in length and females are from 3.8 to 4.4 cm in length (Metcalf & Metcalf, 1993). Migratory Grasshopper. This grasshopper is 2.2 to 2.9 cm in length when mature and is brownish-red to gray in color. The hind legs are marked with a series of black bands. There is a projection on the ventral side between the mid• dle pair of legs (McBride et aI., 1987). The migratory grasshopper is similar in size and shape to the red-legged grasshopper but the hind legs are a paler red or pink color. Newly emerged grasshoppers have black bands on the dorsal surface of their thorax (Metcalf & Metcalf, 1993). Twostriped Grasshopper. The twostriped grasshopper is brown or gray• green with two pale yellow or cream-colored stripes running from the eyes to the wing tips on the upper side of the body. The yellow hind legs have a distinct black stripe. This is a large grasshopper, males are 3.2 to 3.8 cm and females are 3.8 to 4.8 cm in length. The body is robust. Immature stages are green to yellow-brown in color (McBride et aI., 1987; Metcalf & Metcalf, 1993). SUNFLOWER INSECTS 195

Redlegged Grasshopper. The redlegged grasshopper is less than 2.5 cm when full grown. It is brownish-red in color with the tibia of the hind legs being pinkish with black spines (McBride et aI., 1987). Clearwinged Grasshopper. Adults are yellow to brown in color and are marked with large, dark-brown spots on the body and forewing. The hind wings are nearly transparent (Metcalf & Metcalf, 1993). They are about 1.9 cm in length (McBride et aI., 1987).

Life History Grasshoppers found in sunflower are general feeders that attack most cul• tivated and many weedy plants. Oviposition is mainly in uncultivated soil at field margins, along roadsides, in pastures, ditches, and drift soil. Oviposition begins in late July and continues into fall. Eggs are laid in the soil in pods containing 20 to 120 eggs. The egg is the overwintering stage for most species. Egg hatch begins in late April and is usually complete by late June. Immature grasshoppers or nymphs pass through four to six stages and take 40 to 60 d before reaching maturity (McBride et aI., 1987). Nymphs resemble adults except in size and for the lack of wings. Feeding continues until frost (Metcalf & Metcalf, 1993). Grasshopper infestations usually do not originate in sunflower. Sunflower is a secondary host for grasshoppers migrating from weeds and small grains that have matured or been harvested (Adams & Gaines, 1950).

Damage Grasshoppers will feed on all aboveground parts of sunflower but damage is greatest to foliage and developing seed. Damage is sporadic but occasionally complete defoliation occurs. Dry fall weather prolongs the egg-laying period, and during dry springs, survival of nymphs increases. Outbreak conditions develop after several years of hot, dry weather (McBride et a!., 1987).

Management Strategies Because young nymphs are more susceptible to insecticides and their pop• ulations are restricted to smaller areas than older grasshoppers, less insecticide is needed for their control. Several insecticides are registered for grasshopper con• trol. If grasshoppers are a perennial problem, cultural controls can be used. Cultural controls are aimed at reducing the numbers of overwintering eggs or at concentrating eggs or nymphs to facilitate chemical control. Late-summer removal of weeds in fallow strips and other oviposition sites will reduce the num• ber of eggs oviposited. Early season elimination of all green vegetation from fal• low sites will cause the emerging nymphs to starve since they can move only a short distance before feeding. Conversely, trap strips of weeds or grains can be cultivated to attract ovipositing females and concentrate egg deposition in spe• cific areas. The emerging grasshoppers can then be more easily treated with insecticides the following spring. Nymphs can similarly be concentrated in trap strips in otherwise fallow fields. These can then be treated with insecticides (McBride et aI., 1987). 196 CHARLET ET AL.

Aphids [Homoptera: Aphididae]

Members of the genus Helianthus serve as hosts for several species of aphids. Aphis he/ianthi Monell and Masonaphis masoni (Knowlton) are two of the more common aphid species. Species of Aphis are often found on annual Helianthus, whereas Dactynotus, another common aphid genus, is often found on perennial Helianthus (Rogers et ai., 1978b).

Description Aphids are small, soft-bodied insects that are often found in clusters. They have a rapid generation time and reproduce asexually. A pair of tubes (cornicles) on the upper side and toward the back of the abdomen are distinguishing charac• teristics. They feed by sucking plant juices through stylet-shaped mouthparts that are inserted into the plant tissues. Adults exist as winged and wingless forms, and immatures resemble adults except for size and are wingless. Both adults and immatures are found together and are injurious.

Life History Little is known of the life history of sunflower aphids. Several of the species appear to have Helianthus as the primary host, but for others, Helianthus is a secondary host. Aphis sp. are found from the upper Great Plains to Mexico (Rogers et ai., 1978b).

Damage Moderate M masoni populations cause little damage to Helianthus but heavier infestations can stress the plant. The initial symptom is usually wilting, a continued heavy infestation will kill the plant. Aphids are of concern on Helianthus not only for their direct damage but also as vectors of mosaic virus diseases (Rogers & Thompson, 1978c).

Management Strategies Aphids on Helianthus serve as host to numerous parasitoids, including both native and imported species. The effect of the parasitoids and other natural ene• mies serve to keep aphid numbers in control (Rogers et ai., 1972). Some species of perennial Helianthus are resistant to M masoni (Rogers & Thompson, 1978c).

Painted Lady or Thistle Caterpillar, Vanessa cardu; (L.) [Lepidoptera: Nymphalidae]

Vanessa cardui is probably the most widely distributed butterfly species in the world and has a broad host range of over 100 food plants (Williams, 1970). Larvae feed primarily on Canada thistle [Cirsium arvense (L.) Scop.] and help reduce populations of this noxious weed (Westdal, 1975). The painted lady has been an occasional pest of sunflower in Canada, the USA, and Mexico (Westdal, 1975; Schulz, 1978; Vargas et ai., 1980). Vanessa cardui makes seasonal migra- SUNFLOWER INSECTS 197 tions to summer feeding areas and to overwintering sites in Mexico (Williams, 1970). Rogers (l988a) reported that H. annuus is among its most common natur• al hosts.

Description The painted lady is a colorful butterfly about 25 mm long with brown upper wings marked with red and orange mottling and white and black spots (Color Plate 12). Each hind wing possesses a row of one obscure and four distinct eye• spots. The wingspread of the adult is about 50 mm. Eggs are spherical and white in color. Larvae are brown to black with numerous spines and a pale yellow stripe along each side. When fully grown, larvae are 30 to 35 mm long. The pupa is about 25 mm in length and gold in color (Westdal, 1975).

Life History Adults migrate to the northern areas of North America from overwintering sites in Mexico, arriving in early June. Eggs are laid on food plants and hatch in about 1 wk. Larvae feed on leaves, producing a loose webbing that covers them (Color Plate 13). The black fecal pellets produced are often found nearby. The chrysalis hangs from the host plant. Butterflies emerge from the chrysalids in about 10 d and begin a second generation (Westdal, 1975). There is no evidence for diapause or the ability of any stage to survive cold winters (Williams, 1970).

Damage Larvae feed on the leaves and, if numerous, can completely defoliate a plant. Occasional outbreaks in the northern Great Plains have resulted in severe damage to cultivated fields (Schulz, 1978).

Management Strategies Heavy parasitization and high infections of bacterial disease limit damage by this insect. Insecticides can effectively be used to control larvae of this pest but are usually not needed (Westdal, 1975; Rogers, 1988a).

Sunflower Beetle, Zygogramma exclamation is (Fabricius) [Coleoptera: Chrysomelidae]

Sunflower beetles are a conspicuous insect in the sunflower field. Their resemblance to the Colorado potato beetle [Leptinotarsa decemlineata (Say)] has generated concern and confusion in proper identification. Although adults of both species are similar in appearance, the sunflower beetle is smaller and colored dif• ferently than the Colorado potato beetle. The sunflower beetle does not feed on potato (Solanum tuberosum L.), and the Colorado potato beetle does not feed on sunflower (Westdal, 1975; McBride & Charlet, 1985). The beetle has been report• ed from native sunflower ranging from Manitoba, Canada (Criddle, 1922), to Arizona (Brisley, 1925). Although the sunflower beetle occurs in most areas of 198 CHARLET ET AL. the USA west of the Mississippi, economic damage has been confined to the northern Plains and Manitoba (Westdal, 1975; Charlet, 1992).

Description The adult is 6 to 8 mm long with a reddish-brown head and cream-colored thorax with a reddish-brown patch at the base (Color Plate 14). Each elytron is creamy-white with three dark stripes that extend the entire length. A shorter, lat• eral stripe ends at the middle of the wing in a small dot resembling an exclama• tion point. Eggs are cigar-shaped, yellow to orange in color, and 1.5 to 2 mm in length. Larvae are yellowish-green, humped-back, and about 10 mm long at maturity (Color Plate 15). The pupa is similar in size to the adult and yellow in color (Westdal, 1975).

Life History Adults overwinter in the soil and emerge during May and feed on the first available foliage of sunflower (Charlet, 1991a). Beetles mate shortly after emer• gence, and eggs are deposited singly on the stems or undersides of sunflower leaves (Westdal, 1975; Charlet, 1992). In Manitoba, females laid a total of 968 and 636 eggs per female in 1976 and 1977, respectively (Gerber et aI., 1979). The oviposition period lasts 6 to 7 wk. Larvae pass through four instars (Rogers, 1977a) and are present in the field for about 6 wk. Mature larvae enter the soil to pupate in earthen cells. The pupal period lasts 10 to 14 d. New generation adults emerge at the end of July or the beginning of August (Charlet, 1992). The adults re-enter the soil after a couple of weeks to overwinter. New generation adults do not mate and no eggs are developed before entering the soil. There is one gener• ation per year in the northern Plains (Westdal, 1975; Gerber et aI., 1979; Charlet, 1992).

Damage Adult feeding on leaf edges can be distinguished from larval feeding that occurs over the entire leaf surface. Adults feed throughout the day, whereas the larvae feed mostly at night and spend the day hidden in the terminal growth area. Population densities of only two adults per plant and the resulting larval feeding can reduce seed yield by over 20% (McBride & Charlet, 1985). Westdal (1975) found that larval popUlations of 25 or more per plant can completely defoliate a plant and reduce yields by as much as 30%. Late-season feeding by the new gen• eration of adults normally causes minimal plant damage. Control measures are advised if defoliation reaches 25 to 30% and larvae are still in the early stages of growth (McBride & Charlet, 1985).

Management Strategies Application of insecticides when larvae are actively feeding has been shown to be effective in preventing economic damage (Westdal, 1975). Resistance to feeding or reproduction has been shown in approximately one-half of the native sunflower species. Perennial species exhibited antibiosis to both lar- SUNFLOWER INSECTS 199 vae and adult in the laboratory (Rogers & Thompson, 1978b, 1980). Natural ene• mies include a number of general predators such as coccinellids, pentatomids, and the carabid, Lebia atriventris Say, that feed on both eggs and larvae (Westdal, 1975). Paras ito ids also attack all stages of the sunflower beetle. Erixestus winne• mana Crawford (Hymenoptera: Pteromalidae) was reared from eggs, Doryphorophaga macella Reinhard (Diptera: Tachinidae) from the larvae, and Myiopharus sp. (Tachinidae) from the adults (Westdal, 1975; Charlet, 1992). Parasitism by D. macella may have contributed to the reduction of the field infes• tations of the sunflower beetle in the northern Plains in recent years (Charlet, 1992).

HEAD FEEDING SPECIES

Sunflower Moth, Homoeosoma electellum (Hulst) [Lepidoptera: Pyralidae]

Except in North Dakota, South Dakota, and Minnesota where the red sun• flower seed weevil, Smicronyx fulvus LeConte, causes more yield loss (Charlet et aI., 1987), the sunflower moth is the most widespread and damaging pest of sun• flower in North America (Schulz, 1978). It occurs from Mexico to both coasts of the USA and to the Canadian prairie provinces.

Description The adult is a small shiny-gray moth (Color Plate 16). The fringed hind wings are devoid of markings but the front wings have a small dot near the cen• ter. There are two or three smaller dots towards the distal end of the wing. However, the wing markings may be faint and difficult to detect. At rest, the wings are held alongside the body. The larva has alternate dark and light stripes running longitudinally on a buff-colored body (Wesdal, 1975) (Color Plate 17).

Life History Eggs are deposited on the surface of open sunflower heads and hatch in 4 to 5 d (Drake & Harris, 1926; Satterthwait & Swain, 1946). Larvae spin a web over the face of the sunflower head, which accumulates disk flowers and frass. This gives a trashy appearance to the head (Satterthwait & Swain, 1946). Mature larvae move to the ground where they spin cocoons in which they overwinter (Carlson, 1967; Teetes & Randolph, 1970). The first appearance of moths and larvae each season depends on the lati• tude of the location. Infestations are first seen in Texas in early May and are found in North Dakota and the Canadian prairie provinces in August (Arthur & Bauer, 1981). Infestations are frequent and severe in the southern portion of its range (Randolph et aI., 1972). In the northern limits of their range, the sunflower moth does not overwinter due to the severity of the cold (Arthur, 1978). Infestations in those areas are sporadic and dependent on migration aided by southerly winds (Arthur & Bauer, 1981; Beregovoy, 1985a). 200 CHARLET ET AL.

The host range of the sunflower moth includes wild and cultivated H. annu• us, H. petiolaris, H. maxmilliani, and H. debilis. Other species of Compositae including the musk thistle, Cardus nutans L., are hosts. Sunflower moth on C. nutans is beneficial, although it is usually too low in numbers to provide effec• tive control (Teetes & Randolph, 1969; Morihara & Balsbaugh, 1976; Depew, 1986).

Damage First instars feed primarily on pollen. Second instars feed on pollen, and larvae may burrow through the corolla to feed on pollen inside disk flowers. Larvae in the corollas also feed on anthers and styles. Feeding by third instars may sever the style and prevent the ovary from being fertilized, resulting in empty seeds. Third instars also begin feeding on ovaries. Larval feeding to matu• rity results in an average of about 96 damaged disk flowers and about 23 dam• aged ovaries per larva (Rogers, 1978). As they feed, larvae spin a webbing over the face of the sunflower head. The accumulated debris in the larval webbing and damage due to larval feeding predispose the head to Rhizopus infection. Rhizopus further reduces yield and results in rancid oil (Rogers et al., 1978a; Klisiewicz, 1979).

Management Strategies A number of tachinid and hymenopteran parasitoids (Teetes & Randolph, 1969; Beregovoy, 1985b) attack the sunflower moth and aid in its control, but other methods are often needed to protect commercial sunflower from economic loss. Sex-pheromone traps can be used to monitor populations (Underhill et al., 1982). In Kansas, early June plantings usually have higher infestations than later plantings (Aslam & Wilde, 1991 b). However, in other locations, planting dates will have to be adjusted for conditions such as moth flight, available moisture, and length of the growing season (Muma et al., 1950; Teetes & Randolph, 1971; Mitchell et al., 1978). Plant resistance is used to manage the European sunflower moth, H. neb• ulella (Hubner) (=H. nebulellum Denis and Schiffermiiller) (Kiewnick, 1964). The resistance is due to phytomelanin, a hard, acellular layer that develops between the hypodermis and sclerenchyma in the peri carp of some sunflower lines (Rogers et al., 1982). Phytomelanin also imparts mechanical resistance to the North American sunflower moth (Rogers et al., 1982) and chemical precur• sors to phytomelanin may be involved in the resistance (Waiss et al., 1977). Sunflower and other Helianthus species have simple, noncapitate glandu• lar, and capitate glandular trichomes (Spring et al., 1987). At least six different sesquiterpene lactones are produced by the capitate trichomes (Spring et al., 1987). According to two studies, sesquiterpene lactones are feeding deterrents and toxins to the sunflower moth (Gershenzon et al., 1985; Rogers et al., 1987). However, Rossiter et al. (1986) did not find that sesquiterpene lactones are toxic to the sunflower moth, although they were feeding deterrents. SUNFLOWER INSECTS 201

Other sunflower compounds also affect sunflower moth development. Sunflower diterpenes in artificial diet result in reduced larval performance (Elliger et aI., 1976; Rogers et aI., 1987). Sunflower diterpenes also are toxic to the western com rootworm (Diabrotica virgifera virgifera LeConte) (Mullin et aI., 1991) and certain fungal pathogens (Pickman et aI., 1990). The microbial insecticide, Bacillus thuringiensis (Berliner), can be used to suppress sunflower moth infestations (Rogers et aI., 1984) and may be as effec• tive as organophosphate insecticides (Chandler & Heilman, 1982). Sunflower is rich in phenolic compounds which, by themselves, do not affect sunflower moth development. However, some sunflower phenolics synergize the effect of B. thuringiensis on the sunflower moth (Brewer & Anderson, 1990). Despite the research on cultural and biological controls and plant resis• tance, the control method of necessity is usually an insecticide. Various insecti• cides are effective and are registered for sunflower moth control (Archer et aI., 1983; Depew, 1983; Bynum et aI., 1985).

Sunflower Midge, Contarinia schulzi Gagne [Diptera: Cecidomyiidae]

Several species of midge are reported from sunflower, but only the sun• flower midge and the sunflower seed midge, Neolasioptera helianthis (Felt), are economic pests (Schulz, 1973; Kreitner & Rogers, 1981). Although, the sun• flower midge is distributed throughout the Great Plains of North America from Manitoba to Texas, its economic impact has been restricted to sunflower in the Red River Valley of North Dakota, Minnesota, and Manitoba (Rogers et aI., 1979).

Description Adults are small (2-3 mm), delicate insects (Color Plate 18). They often are not seen, but when infestations are high, dead adults may be found on sunflower buds. Eggs are yellow and are laid singly or in masses of about 50 in the depres• sions between the involucral bracts of the sunflower bud. Larvae are 1 to 2 mm in length and are generally white in color (Anderson, 1989). Larvae are most eas• ily found at the base of the involucral bracts (Color Plate 19).

Life History In North Dakota, pupation occurs in the spring with adult emergence begin• ning in late June. Adults live only 2 to 3 d and are difficult to detect (Kopp & Busacca, 1983). Buds are preferred for oviposition I to 2 wk prior to pollen shed, but receptacles of all stages and even leafaxils receive eggs when infestations are high. The females prefer large buds and buds with open centers for oviposition (Anderson & Brewer, 1991). Larval development is complete in 10 to 14 d. Mature larvae drop from the head and burrow into the soil. If conditions are favorable, they pupate and emerge the same season. Otherwise, they remain in the soil and overwinter as larvae in cocoons or, in some cases, as pupae. The life 202 CHARLET ET AL. cycle ranges from 31 to 35 d and there can be several generations per year (Samuelson, 1976). The sunflower midge is restricted to the genus Helianthus and has been found on H. annuus, H. maxmilliani Schrad., H. petio/aris Nutt., and possibly H. ciliaris D.C. (Schulz, 1973; Rogers, 1977c; Rogers et aI., 1979; Charlet et aI., 1992).

Damage Newly hatched larvae migrate to the base of the bracts and their feeding produces necrotic feeding depressions between the bracts (Samuelson, 1976; Anderson, 1989). These appear as brown scar tissue and are usually the first symptom of a midge infestation. Another early symptom is the loss of ray flow• ers. Second- and third-instar larvae move to the center of the head and feed at the base of developing seeds where they may cause seed abortion. If sufficient num• bers of larvae are present, head growth is altered. Heavily damaged heads are gnarled and cupped inwardly, often with a hole or depression in the center, and produce few or no seeds (Samuelson, 1976; Anderson, 1989) (Color Plate 20). Economic damage may be severe but is sporadic and localized. Damage is usually restricted to field margins but, in severe infestations, damage is present throughout the field. In some cases, damage has been sufficient to result in fields being abandoned (Fick & Auwater, 1981)

Management Strategies Insecticides can control the sunflower midge if applications are timed just prior to adult emergence. However, because of the difficulty in predicting the emergence of adults, insecticide applications are usually not effective (Anderson, 1989). Delayed planting will usually avoid the major, first emergence of the over• wintering population, although under favorable conditions later infestations can be severe. Late planting, however, can make infestations of other insects, such as the red sunflower seed weevil, more severe (Oseto et aI., 1987). Some commercial hybrids are tolerant or resistant to the sunflower midge. Current sources of resistance affects larval development and survival and adult ovipositional preference (Anderson & Brewer, 1991). Growth deformity of sunflower heads that results from sunflower midge infestation is probably due to elevated auxin levels. A method of simulating sun• flower midge damage by treating sunflower buds with synthetic auxin can be used to select for resistance to the sunflower midge (Brewer et aI., 1994). Bracken (1991) developed a simple and reliable six-point scale for rating sunflower lines for sunflower midge damage. The scale is based on a visual esti• mate of relative area of seed destroyed as well as the degree of head cupping. Brewer et ai. (1994) described a quantitative method that relies on changes in head shape to estimate sunflower midge damage. Their method can be used to rate sunflower hybrids for both natural and simulated sunflower midge damage. Both the Bracken (1991) and the Brewer et ai. (1994) methods give values that are significantly correlated with yield loss. SUNFLOWER INSECTS 203

Red Sunflower Seed Weevil, Smicronyx fulvus LeConte [Coleoptera: Curculionidae]

The red sunflower seed weevil occurs from the Appalachian mountains westward through the Great Plains and to the Pacific Northwest (Anderson, 1962). It is a consistent, economic pest of sunflower in the Dakotas and Minne• sota and is the most common of the two sunflower seed weevil species in the northern latitudes (Gednalske & Walgenbach, 1982; Charlet et aI., 1987).

Description Red sunflower seed weevil adults are 2.5 to 3 mm long and are covered with reddish-orange, oval scales (Color Plate 21). As the weevils age, the scales rub off and the weevils become darker in appearance. The rostra or snout is black and slightly curved (Anderson, 1962). Eggs are white and average 0.28 mm wide and 0.70 mm long (Oseto & Braness, 1979a). Small larvae are cream-colored, legless, and about I to 2 mm long. Larvae are found inside and usually in the upper third of developing sunflower seeds (Color Plate 22). Larvae and pupae of the red sunflower seed weevil are described by Oseto and Braness (1979b).

Life History Adults appear during late June on volunteer sunflower and feed on the involucral bracts where they form pinpoint holes. As the bud develops and opens, adults move to the inflorescence and feed on pollen produced by the disk flowers (Korman & Oseto, 1989). After a preoviposition period of approximately 2 wk, females oviposit inside the pericarp of developing seeds. Weevil populations are highest on plants at 50% anthesis. Adults leave plants that have completed anthe• sis and move to other plants that are still shedding pollen. Adult longevity is about 53 d. Adult weevils do not readily fly and remain hidden among the disk flowers (Oseto & Braness, 1979a). Eggs are oviposited through the hull and are appressed to the developing kernel. Egg placement is normally in the upper end of the achene. The oviposi• tion pattern follows seed filling which progresses from the periphery to the cen• ter of the head. Usually, an infested achene contains a single larva, but approxi• mately 12% of the achenes contain two or more larvae. Oviposition lasts 20 d (Oseto & Braness, 1979a). Larvae eclose in the developing kernel and develop through five instars (Oseto & Braness, 1979b). In late August, fifth instars chew an exit hole in the seed, drop to the ground directly beneath the drooping sunflower head, and over• winter in the soil (Oseto & Charlet, 1981). Peng and Brewer (1995a) described a method to contrast seed damaged by exiting seed weevil larvae and by sunflower moth and banded sunflower moth larval feeding. Larvae continue to emerge from the seeds for 30 d, and pupation occurs in the soil during early June through early July. Oseto and Braness (1979a) found the red sunflower seed weevil on various species of Helianthus including, H. annuus, H. maximiliani, H. petiolaris, and H. tuberosus. However, they did not recover larvae from H. tuberosus. Charlet et al. (1992) collected adults from the above species plus H. rigidus (=pauciflorus) and 204 CHARLET ET AL.

H. nuttallii. In addition to Helianthus, Tuttle (1952) collected adults from iron• weed, Veronia interior Small, and Heliopsis helianthoides L.

Damage Larval feeding reduces seed weight and oil volume. The oil concentration loss is attributed to larva feeding on the seed and not on the hull. Oil loss from damage to the hull is insignificant (Oseto & Braness, 1980). Adult feeding on the bracts of developing sunflower does not cause economic damage.

Management Strategies Insecticides remain the major management tool to reduce red sunflower seed weevil damage (Oseto & Burr, 1990) and are applied when the economic threshold equals the cost of management. The economic threshold is based on several variables: the chemical and application costs, market price of sunflower, plant population, and kernel weight and oil content loss attributed to larval feed• ing (Peng & Brewer, 1995b). Peng and Brewer (l995c) describe a sampling method for the red sunflower seed weevil. Insecticide efficacy is maximized if chemicals are applied when the majority of plants are at 10 to 40% anthesis (Oseto & Burr, 1990). Early planting in the northern Plains region of the USA results in lower seed damage than if sunflower is planted late. This occurs because early planted sunflower completes anthesis and is no longer susceptible to oviposition at the time the weevil population peaks. Planting early does not affect seed weight or oil content (Oseto et aI., 1987). However, early planting increases the risk of infestation by the sunflower stem weevil (Oseto et aI., 1982). Fall or spring mold• board plowing can reduce adult emergence (Gednalske & Walgenbach, 1984). The planting of an early flowering border of sunflower around a larger sunflower field can serve as a trap for the red sunflower seed weevil and greatly reduce the cost of insecticide controls (Brewer & Schmidt, 1995). Although insect resistant hybrids are not yet available, Brewer and Charlet (1995) describe the red sunflower seed weevil resistance of six sunflower acces• sions. Both larval antibiosis and adult nonpreference were detected. Population levels of natural enemies are insufficient to control the red sun• flower seed weevil. Natural enemies of larvae in the seed include the parasitic Hymenoptera, Bracon mellitor Say, Nealiolus curculionis (Fitch), Trimeromicrus spp., Torymus albitarse Huber, Eupelmus cyaniceps amicus Girault, and Zyglyptonotus schwarzi Crawford. The parasitoids attack about 5.1 % ofthe lar• vae in the seeds. Stilleto fly (Diptera: Therevidae) larvae, Thereva candidata Loew and Rucifera rufiventris Loew, accounted for a 3.1 % predation rate of lar• vae and pupae in the soil (Oseto & Braness, 1979a).

Gray Sunflower Seed Weevil, Smicronyx sordidus LeConte [Coleoptera: Curculionidae]

The gray sunflower seed weevil is found on sunflower from Mexico to Texas to the Canadian prairie provinces of Manitoba and Saskatchewan SUNFLOWER INSECTS 205

(Anderson, 1962; Zak, 1976). It is more common in the southern regions than the red sunflower seed weevil (Rogers, 1988a).

Description The gray sunflower seed weevil is covered with gray scales but old adults may be black because of the loss of scales (Anderson, 1962) (Color Plate 23). Eggs are nearly elliptical to oval with one end distinctly larger than the other. Egg length averaged 0.7 mm with widths at the two opposite ends being 0.2 and 0.3 mm (Stober, 1993). Except for the width differences in the two ends of the egg, shape and size of the gray sunflower seed weevil egg resembles that of the red sunflower seed weevil. The larvae resemble red sunflower seed weevil larvae in color and shape but are larger (3-3.5 mm). They are internal seed feeders and are usually found near the bottom of the developing seed (Brewer, 1991) (Color Plate 24).

Life History Adults begin emerging from the soil in late June and early July, 2 to 3 wk earlier than adults of the red sunflower seed weevil (Gednalske & Walgenbach, 1984). Unlike the red sunflower seed weevil which oviposits internally in the seed and occurs on plants during anthesis (Oseto & Braness, 1979a), gray sun• flower seed weevil oviposition is external and occurs while the plant is in the bud stage (Brewer, 1991). Eggs are placed in the tips of immature disk flowers and larvae move through the corolla tube to reach the developing ovary. The larvae then migrate to the base of the seed to feed (Brewer, 1991; Stober, 1993). The lar• vae pass through four instars (Stober, 1993). Once the plant reaches the anthesis stage, it is no longer attractive to the gray sunflower seed weevil and it will leave the plant (Byers, 1987; Brewer, 1991). Seeds infested by larvae of the gray sun• flower seed weevil enlarge, protrude above surrounding seeds, and lack a kernel. Enlarged seeds are apparent at 16 d after oviposition (Stober, 1993) and may be a type of gall (Brewer, 1991). At maturity, larvae chew an exit hole in the peri• carp and drop to the ground. Larval emergence begins about 46 d after oviposi• tion (Stober, 1993). Adult gray sunflower seed weevils have been found on wild and cultivated H. annuus, H. coronatus, H. argophyllus, and H. maximiliani. However, it is not known if all the species were larval hosts (Anderson, 1962, Charlet et aI., 1992). Other associated plants include Silphium perfolliatum, S. terebinthaceum, Medicago sativa, and Cassia spp. (Anderson, 1962).

Damage The damage caused by a single larva of the gray sunflower seed weevil exceeds that ofthe red sunflower seed weevil because of the loss ofthe entire ker• nel (Brewer, 1991). However, total damage due to the gray sunflower seed wee• vil is usually less than that of the red sunflower seed weevil because of its lower population level (Gednalske & Walgenbach, 1984) and because the reproductive rate is lower (Brewer, 1991). However, damage may escalate as a result of 206 CHARLET ET AL. increasing gray sunflower seed weevil populations (Gednalske & Walgenbach, 1984).

Management Strategies Gednalske and Walgenbach (1984) found that pyrethroid insecticides reduced infestations of seed weevils in commercial sunflower. However, because they did not distinguish between infestations of gray and red sunflower seed wee• vils, it is not possible to determine if a reduction in the gray sunflower seed wee• vil infestation occurred. They note that if large populations of the gray sunflower seed weevil with their earlier emergence dates occur, insecticide application tim• ing will need to be adjusted. Tillage treatments, especially disking and moldboard plowing, reduce emergence of overwintering adults. Larvae in the soil are susceptible to Metarrhizium, a fungal pathogen (Byers, 1987). A number of hymenopterous parasitoid species were recovered from native sunflower species in the northern Great Plains that attack larvae of both the gray and red sunflower seed weevil (Charlet & Seiler, 1994).

Banded Sunflower Moth, Cochylis hospes Walsingham [Lepidoptera: Cochylidae]

The banded sunflower moth has been reported from the Dakotas, Minnesota, and Wisconsin, east to Indiana, Ohio, North Carolina, and north to New Jersey. The moth has been co1lected in pheromone traps in Iowa, Kansas, Arkansas, Texas, and Oregon (Beregovoy et aI., 1989). It also attacks sunflower in the Canadian prairie provinces of Saskatchewan and Manitoba (Westdal, 1949; Arthur & Campbe1l, 1979). Based on this widespread distribution, the moth prob• ably occurs wherever wild Helianthus spp. grow. Charlet et aI. (1992) recorded the larvae from heads of six species of native Helianthus in eastern North Dakota. Rogers (1988a,b) also recorded the moth from three additional species of sun• flower. Banded moth damage has increased in central and east-central North Dakota (Charlet et aI., 1987; Charlet et aI., 1995). Aslam and Wilde (1991a) noted that the moth is a potential pest in Kansas due to increasing populations in the state. Recently Arthur and Powell (1990) described a new species of Cochylis from sunflower in Saskatchewan. Cochylis arthuri Dang has comparable feeding habits and development, and causes damage similar to that of C. hospes. It also has been found in sunflower from North Dakota, but is much less common than the banded sunflower moth.

Description The adult moth measures 6 mm. Light-tan body scales cover the body. A distinct, dark-brown triangular scale patch covers the midportion of the forewings, and the edge of the forewings has a sma1l, brown patch of scales (Color Plate 25). Eggs are 0.45 mm long and 0.29 mm wide. Egg color changes from white to light-brown as the egg matures. The body color of larvae differs SUNFLOWER INSECTS 207 among instars. The early instars are light pink and late instars are red or red and green in color (Westdal, 1949; Charlet & Gross, 1990).

Life History Moths spend much of their time in vegetation along field margins during the day. At twilight, females move into the fields to oviposit. Dissection of moths indicate that females mate before they enter sunflower fields (Beregovoy & Riemann, 1987). Moths flutter from plant to plant but do not feed. The average life span of adults is 7 to 10 d. Moth flight lasts 8 wk (2 mos) (Beregovoy et aI., 1989). Oviposition begins during early July and continues for approximately 6 wk. Females oviposit more eggs on prebloom than on early bud or postbloom sunflower. The majority of eggs are oviposited on the outer whorl of the involu• cral bracts, and some eggs are oviposited on the underside of the sunflower head. Incubation period of the eggs is approximately 7 d. Newly emerged larvae are found on the involucral bracts and they later move to the disk flowers and feed on pollen. Third instars tunnel through the disk flowers and feed on young devel• oping seeds (Color Plate 26). As the seeds mature and harden, larvae chew into the seeds. Each larva will penetrate and consume the contents of several seeds. At maturity, larvae drop from the head and enter the soil to overwinter in silken cocoons. There are five larval instars. Pupation occurs in late June. Some larvae may leave the cocoon and pupate in the soil (Westdal, 1949; Beregovoy & Riemann, 1987; Charlet & Gross, 1990). Barker (1993) determined that the moth has a facultative diapause, but that conditions in the northern Plains induce dia• pause. Whereas, more than one generation is possible in the southern regions, a suggestion also made by Beregovoy et al. (1989).

Damage Newly hatched larvae of the banded sunflower moth move from the bracts to the disk flowers of the sunflower head, where they enter open disk flowers. Larvae feed on disk flowers, unfertilized seeds, and developing and mature seeds (Westdal, 1949; Charlet & Busacca, 1986). Consumption of disk flowers may adversely affect yield in sunflower since studies simulating damage by disk• flower removal showed that heads did not compensate for lost disk flowers dur• ing seed filling (Charlet & Miller, 1993). After feeding on the kernel ofa mature seed, the larva moves to a new seed. Each larva consumes more than six mature seeds (Charlet & Gross, 1990). Banded sunflower moth larval damage to the seed is similar to damage caused by the seed weevil. The banded moth larva normal• ly consumes the entire kernel, and the seed weevil larva consumes a third of the kernel. The exit hole in the seed created by the banded moth larva is slightly larg• er than the exit hole created by the seed weevil larva.

Management Strategies Pheromone traps baited with female sex pheromone can be used to moni• tor populations and flight phenology of the moths (Underhill et aI., 1986; Beregovoy & Riemann, 1987; Beregovoy et aI., 1989). Scouting strategies and 208 CHARLET ET AL. the economic threshold for the banded sunflower moth were reported by Charlet et al. (1995). Insecticide efficacy can be maximized if application timing is based on the plant developmental stage. Chemicals applied to sunflower at late bud stage (R4 = yellow ray flowers visible in the bud) significantly reduced banded sunflower moth damage, whereas insecticides applied to sunflower 2 wk after the susceptible R4 stage failed to reduce banded sunflower moth damage (Charlet & Busacca, 1986). Damage caused by the banded sunflower moth can be minimized by manipulating planting dates to avoid oviposition. Sunflower planted late (early June) in southeastern North Dakota had less damaged seeds than sunflower plant• ed early (1st wk in May). Seed weight and oil content varied from year to year and did not appear to be correlated with planting dates (Oseto et aI., 1989). Brewer and Charlet (1989) reported that resistance to the banded sunflower moth was present in some sunflower germplasm and Charlet and Brewer (1995) noted resistance in some species of native sunflowers. Further progress in developing resistant lines depended on improvement of artificial infestation techniques. Eggs and young larvae are preyed upon by Orius tristicolor White (Hemiptera: Anthocoridae) and larvae are parasitized by the ichneumonid wasp, Glypta prog• natha Dasch. Other predators found feeding on sunflower heads included Nabidae, Chrysopidae, and Coccinellidae. Ground beetles were found to destroy about 40% of overwintering larvae and pupae (Bergmann & Oseto, 1990). The parasitoid, Chelonus phaloniae Mason (Hymenoptera: Braconidae), also causes larval mortality (Westdal, 1975; Bergmann & Oseto, 1990). Two additional bra• conid parasitoids reared from banded sunflower moth larvae include Bassus arthurellus Sharkey (1985) and Bracon mellitor (Say) (Sharkey et aI., 1987).

Sunflower Receptacle Maggot, Gymnocarena diffusa (Snow) [Diptera: Tephritidae)

The sunflower receptacle maggot is a common species restricted to the Great Plains from Montana south to Arizona and east to Missouri.

Description Adult G. diffusa measure 7.6 to 7.8 mm long. The yellow to light-brown body has a pair of distinctively marked wings typical of members of the Tephritidae (Color Plate 27). A transverse hyaline band extends from the leading edge of the wing to the posterior margin. Initially the eggs are white but they change to a light-brown color as they age. Instars 1 and 2 are white and range in size from 1 to 4.5 mm, respectively. The third instar is yellow to light-brown and about 7.8 mm in length. The pupa is located on the receptacle or in the soil, is egg-shaped and black, and about 7.0 mm in length (Kamali & Schulz, 1973).

Life History Adults first appear in North Dakota in late June. Males begin mating 5 d after emergence, however, females require a preoviposition period of 15 to 20 d. SUNFLOWER INSECTS 209

Under greenhouse conditions, adults live an average of 30 d. At the time of emer• gence, wild and volunteer sunflower have buds that are attractive to the adult flies. The adults feed on glandular secretions found on the sunflower receptacle. As commercial sunflower begins to bud, these plants become attractive to the adult flies. Eggs are placed on the inner surface of the involucral bracts, usually between the second and fourth layers of bracts. First-instar larvae are most often found at the base of the involucral bracts, while older larvae are located in the receptacle (Color Plate 28). The larval period lasts about 20 d. At maturity, most larvae drop to the soil through a hole on the underside of the receptacle and pupate at a depth of about 3 cm. A few larvae remain in the receptacle or among the seeds to pupate. Gymnocarena diffusa is univoltine and diapauses as a pupa (Kamali & Schulz, 1974). The sunflower receptacle maggot also infests H. annu• us and H. maxmiliani (Charlet et aI., 1992; Kamali & Schulz, 1974).

Damage The maggot feeds on the spongy receptacle tissue of the sunflower head. Larvae do not feed on developing seeds. No adverse effects oflarval feeding have been reported.

Management Strategies Control for G. diffusa has not been necessary. A few natural control agents have been recorded. A parasitic wasp, Perilampus sp., was reared from a G. dif• fusa pupa, and a fungus, Aspergillus sp., infected G. diffusa pupae. An unidenti• fied mite has been reported on the thoracic and abdominal pleura of adults (Kamali, 1973).

Sunflower Seed Maggot, Neotephritis finalis (Loew) [Diptera: Tephritidae)

The sunflower seed maggot is a common insect infesting the heads of plants in the Asteraceae. It ranges from southern Canada to northern Mexico and throughout continental North America, except for the northeastern USA (Foote & Blanc, 1963). Synonyms for N. finalis include Trypeta finalis Loew, Euribia finalis Hendel, Tephritis finalis Loew, and T. afinis (Kamali, 1973).

Description Adults are small to medium-sized flies. The dark-brown wings have hya• line patches scattered throughout the wing (Color Plate 29). Eggs are smooth, translucent-white, ellipsoid in shape with tapered anterior and blunt posterior ends, and measure 1.15 mm long by 0.27 mm wide. Eggs are oviposited singly between the disk flowers (Goeden et aI., 1987). Mature larvae are 4.5 mm long and 1.5 mm in diameter and are found at the base of disk flowers and developing seeds (Kamali, 1973). 210 CHARLET ET AL.

Life History The sunflower seed maggot is a bivoltine tephritid fly with a partial third generation present during abnormally warm falls. In North Dakota, first-genera• tion adults are present in sunflower fields during the 1st wk in July and second• generation adults are found from mid- to late August (Kamali, 1973). In the greenhouse, females have a preoviposition period of 28 to 31 d. A mean of 36 eggs are produced within a 22-d period. Eggs are laid on the sides of unopened disk flowers or floral bracts. The egg stage lasts 4 d, and the larval stadium is 14 d. Larvae infest sunflower in early August and feed on sunflower seeds (Color Plate 30). The first generation pupates in the seeds and the pupal period lasts 8 to 9 d. The second generation overwinters as pupae in the soil. The sunflower seed maggot has been collected from H annuus, H graci• lentus, H niveus, H nuttallii, H maximiliani, H tuberosus, and H rigidus (=pauciflorus) (Charlet et al., 1992; Goeden et al., 1987). Besides Helianthus, other Asteraceae hosts include Actinomerus sp., Encelia californica Nutt., Dahlia sp., Eriophyllum lanatum, Helianthella uniflora, Wyethia mollis, Balsamorhiza sp., and Chrysothamnus sp. (Goeden et al., 1987).

Damage Damage varies with the stage of the plant and larval instar. On plants with unfertilized seeds, larvae tunneled into the ovary, resulting in seed sterility. The first instar tunnels into 3 to 6 achenes, second instars through 3 to 9 achenes, and third instars through another 7 to 11 achenes. Larva, regardless of the instar, do not feed on the receptacle (Kamali, 1973; Goeden et al., 1987). Of the three species of Tephritidae attacking the sunflower head, only N. finalis has the poten• tial to reduce seed yields. The damage, however, is slight when compared with other seed-infesting insects (Kamali, 1973).

Management Strategies In the northern Great Plains, N. finalis has not caused significant damage to sunflower seeds. However in Mexico, N. finalis infestations have caused eco• nomic damage (Zak, 1976). Larval or larval-pupal parasites of N. finalis include Eurytoma vernonia Bugbee (Eurytomidae) and Pteromalus sp. (Pteromalidae) (Goeden et al., 1987).

Sunflower Headclipping Weevil, Haplorhynchites aeneus (Bobeman) [Coleoptera: Curculionidae]

The sunflower headclipping weevil is the most common and widespread species of the genus and occurs throughout the USA and north to Manitoba and Saskatchewan, Canada (Hamilton, 1974). It is most abundant in the Midwest, occurring on native species of Helianthus including H annuus, H divaricatus L, H grosseserratusMartens, and H microcephalus Torrey & Gray as well as sev• eral species of Silphium (Hamilton, 1973, 1974). Aslam and Wilde (1991a) recorded damage by the weevil in a number of Kansas locations. SUNFLOWER INSECTS 211

Description The adult sunflower headclipping weevil is the largest of the weevil com• plex attacking sunflower (Charlet et aI., 1987). The body of the adult is shiny black (Color Plate 31). There appears to be no significant size differences between males and females. The body is 3.9 to 6.6 mm long and 2.0 to 3.4 mm wide (Hamilton, 1974). Eggs are ovoid to round and pearly-white to cream-col• ored (Schulz, 1978). Mature larvae are C-shaped, white in color, and about 5 mm in length (Hamilton, 1973).

Life History Males and females appear in July on sunflower at the early bud stage. Mating takes place on the sunflower head. Females oviposit in the base of the disk flowers and then move to the stem, below the head, and create a series of punctures. The punctures encircle the stem and eventually cause the sunflower head to drop to the soil after hanging from the stem for a few days (Color Plate 32). Eggs hatch in I wk. Larval development takes place in the decaying tissue of the sunflower head. First instars feed on pollen and the second and third instars feed on disk flowers. At maturity, fourth-instar larvae leave the heads and enter the soil at the base of the plant to a depth of 30 cm to overwinter. In Illinois, all larvae had left infested heads by the end of October. Larval development took 20 to 30 d. Pupation occurred the 1st wk of July the following year and lasted 10 d (Hamilton, 1973).

Damage Damage is caused by the female sunflower headclipping weevil and is usu• ally confined to plants in the outer rows of the sunflower field. Reports have indi• cated that damage to sunflower is usually insignificant, although losses of up to 10% of fields have been noted by Schulz (1978) in isolated areas of North Dakota. Lynch and Gamer (1980) mentioned that commercial fields had been damaged by this weevil and considered it a potential economic threat to sun• flower production in Georgia.

Management Strategies Insecticides have not been used against this weevil because of the low level of damage. Schulz (1978) reported that the parental lines HA64, HA65, and HA 113 were promising sources of resistance or tolerance to the sunflower head• clipping weevil. He also indicated that crop rotation or location of fields away from previous plantings might provide relief from damage from this pest. Aslam and Wilde ( 1991 a) indicated planting-date differences in damage at certain loca• tions in Kansas.

INSECT PESTS OF SOUTH AMERICA

A variety of insects feed on cultivated sunflower in the South American countries of Argentina, Brazil, and Uruguay. The most important pest of sun- 212 CHARLET ET AL. flower in Brazil is the nymphalid butterfly, Chlosyne lacinia saundersii Doubleday and Hewitson (Paro & Nakamo, .1976; Ungaro, 1978). Lourencao and Ungaro (1983) found that among the sunflower cultivars they tested, defoliation varied between 19 to 58%. The butterfly attacks a number of host plants, includ• ing sunflower. Depending on the plant stage when attacked, yields can be reduced from 73 to 100% (Paro & Nakamo, 1976). In Brazil, the noctuid Rachiplusia nu (Guenee) feeds on leaves and the black cutworm, Agrotis ipsilon (Hufnagel) destroys young plants (Ungaro, 1978). The chrysomelid, Diabrotica speciosa (Germar), defoliated the plants and the scarab beetle, Cyclocephala melanocephala (Fabricius), attacked the heads reducing sunflower yield (Ungaro, 1978). Boica et al. (1984) included a number of additional pests that attacked sun• flower in Brazil: Bemisia sp., aphids, the Brazilian leafhopper (Protalebrella brasiliensis (Baker), Empoasca sp. (Cicadellidae), Liriomyza sp. (Agromyzidae), Leptocorisa tipuloides (DeGreer) (Coreidae), and the noctuids, Pseudoplusia includens (Walker), the velvetbean caterpillar (Anticarsia gemmatalis HUbner), and the fall armyworm, Spodoptera frugiperda (Smith). A list of predators also was included in their survey (Boica et aI., 1984). Larvae of a caterpillar, Actinote pellena pellena HUbner (Nymphalidae), have caused damage to sunflower in Argentina (Rodriquez, 1963). This species also has been reported from Venezuela, Brazil, Paraguay, Uruguay, and Peru (Orfila, 1964). Larvae feed on sunflower leaves which may be skeletonized from the gregarious feeding habit of the larvae. The species has two to three genera• tions in Argentina, and four generations may occur in Brazil. The yellow woolly• bear, Spilosoma virginica (Fabricius) (Arctiidae), has been recorded from Argentina since 1958, where feeding by larvae slows plant development and reduces yield in late-planted sunflower (Rizzo, 1975- 1976). Two species of Homoeosoma are pests of sunflower heads in Argentina. Homoeosoma heinrichi Pastrana damages seeds from sunflower in both Argentina and Uruguay (Pastrana, 1961). Pastrana (1984) described a new species, H vinciniae Pastrana, as a pest damaging disk flowers and immature seeds of sunflower heads in Argentina. Sunflower heads also are damaged by the spotted maize beetle, Astylus atromaculatus Blanchard (Melyridae), which attacks a number of other crops including sorghum, Sorghum vulgare Pers., and maize (Nemirovsky, 1972). Rizzo (1970) listed 17 additional pests from Argentina, including: Athaumastus haematicus (Sud) (Coreidae); Edessa meditabunda (Fabricius) (Pentatomidae); the southern green stink bug, Nezara viridula (L.) (Pentatomidae); Gargaphia torresi C.L. (Tingidae); the black cutworm; the variegated cutworm, Peridroma saucia (HUbner) (Noctuidae); R. nu; Melanagromyza cunctanoides Blanchard (Agromyzidae); Hylemyia spp. (Anthomyiidae); D. speciosa; Disonychodes exclamation is (Boheman) (Chrysomelidae); Conoderus spp. (Elateridae); Epicauta leopardina (Haag-R.) (Meloidae); Acromyrmex spp. (Formicidae); and Diloboderus abderus (Sturm.), Discynetus gagates Burmeister, Ligyrus spp. (Scarabaeidae) . In Uruguay, damage to seedlings is caused by three species of ants [Acromyrmex heyeri (Forel), A. lundi (Guerin), A. striatus (Roger)] and by the black and variegated cutworms (Silveira-Guido, 1962b; Zerbino, 1986). Sunflower is defoliated by Plusia sp., which reduced yield only if feeding SUNFLOWER INSECTS 213 exceeded 25% at the bud stage of development. The moth is attacked by spiders, nabids, pentatomids, carabids, and three species of parasitoids, including Apanteles sp. (Zerbino, 1986). Grasshoppers (Dichroplus platens is Bruner and D. conspersus Bruner) damage both young plants and leaves of more mature plants in Uruguay as well as Argentina, Brazil, and Paraguay (Silveira-Guido, 1962a). A number of species of spider mites also damage sunflower leaves, although usu• ally the damage is not severe (Silviero-Guido, 1962b). Scarabs of the genera Phyllophaga, Cyclocephala, Dyscinetus, Lygirus, Diloboderus, Phileurus, and others destroy roots of sunflower, causing severe losses, especially in areas with soil rich in organic matter (Silveira-Guido, 1962b). Larvae of Hylemyia cilicrura (Rondani) (Anthomyiidae) feed on germinating seeds and have been reported to destroy over 45% of the plants in a field. The flies also occur in Argentina and Brazil (Silveira-Guido, 1962b). The southern green stink bug feeds on sunflower and many other crops in Uruguay, but also is attacked by a number of parasitoid species (Silveira-Guido, 1962a). Diabrotica speciosa adults damage sunflower leaves and floral parts of the head and the larvae feed in the stem and roots of young plants. The pest also occurrs in Bolivia and Paraguay (Silveira-Guido 1962b). Other pests that feed on sunflower foliage in Uruguay include the fol• lowing: Myzus persicae (Sulzer); the black cutworm; the variegated cutworm; and Mallocephala deserticola Bergman (Noctuidae). Rachiplusia nu is consid• ered to be most the important pest of sunflower in Urguary, feeding on leaves, disk flowers, and seeds. Populations of 40 larvae per leaf or 400 per plant have been commonly reported (Silveira-Guido, 1962a). Homoeosoma heinrichi has been a serious pest of sunflower in Uruguay, with up to 42 larvae per head in some fields. Larvae destroy all parts of the head, but prefer mature seeds (Silveira-Guido, 1962a). Silveira-Guido (1962a,b) provided a detailed list of the predators and parasitoids of sunflower pests occurring in Uruguay.

INSECT PESTS OF AFRICA

In Nigeria, as well as other parts of Africa, sunflower has been grown for a long time as an ornamental. As a result, insects feeding on Asteracea have adapt• ed to ornamental sunflower and later moved to the commercial crop (Misari, 1990). The insect pests of sunflower in Africa are polyphagous and attack a vari• ety of crops. Numerous insects attack sunflower in tropical and temperate Africa (Rajamohan, 1976) and are pests or potential pests. Many other species are of minor importance or of sporadic occurrence. However, their combined action may seriously affect yield (Misari, 1990). Over 80 species are pests or potential pests of sunflower in Kenya (Khaemba & Mutinga, 1982). Schmutterer (1969) lists a number of insect pests of northeast and central Africa. Insects attack all parts and stages of sunflower. In the preflowering stage, 51 species attack the roots, stems, and leaves. Root feeding insects include the exclusive root feeder Schizonycha sp. (Scarabaeidae) (Misari, 1990) and several species that feed on roots as well as stems and leaves. These include Gonocephalum simplex Fabricius (Tenebrionidae), the black cutworm, and Agrotis segetum Denis and 214 CHARLET ET AL.

Schiffermti1ler (Noctuidae) (Khaemba & Mutinga, 1982). Root infestations are sporadic and, although at times severe, root damaging insects are usually minor pests. Besides feeding on roots, Agrotis species also attack seedling stems and leaves where they are serious pests. As a group, the noctuids are the most important of the lepidopteran pests. The major noctuid leaf feeder is Plusia orichalcea Fabricius (Khaemba & Mutinga, 1982). It infests sunflower at germination but continues to cause dam• age through the flowering and seed development stages. Plusia orichalcea caus• es heavy defoliation and is widespread in distribution. In Nigeria, the most abundant group of insects during the preflowering stage is the piercing-sucking Hemiptera (Misari, 1990). Macrosteles sp. (Cicadellidae) are very numerous during this period. They feed by sucking sap from leaves and stems and can stunt plant growth. Macrosteles sp. remain com• mon through seed filling. At flowering, a different set of pests attacks the capitulum. Infestations of the fly Dacus cucurbitae Coquillett (Tephritidae) are potentially serious because of rotting by secondary fungal infections (Khaemba & Mutinga, 1982). Developing seeds are attacked by lepidopteran larvae with chewing mouthparts and by hemipteran bugs with piercing-sucking mouthparts (Misari, 1990). Larvae of the noctuid moth, Helicoverpa armigera (Hubner)., infest sunflower just prior to flowering but they cause the most damage during the flowering stage. Young larvae of H. armigera damage disk flowers and older larvae feed on developing seeds and cause a direct yield loss. Older larvae also may burrow into the necks of the capitulum and cause head lodging. Helicoverpa armigera is widespread throughout Africa and is a frequent pest of sunflower (Schmutterer, 1969; Rajamohan, 1976; Bohlen, 1978; Khaemba & Mutinga, 1982; Misari, 1990; van den Berg, 1993). In Egypt, Spodoptera exigua Hubner (Noctuidae) is a serious pest (Salama et aI., 1993). During seed development and filling several hemipteran bugs become important by attacking developing seeds and sucking the seed contents. A major pest of this group is Nezara viridula (L), the southern green stink bug (Penta• tomidae). It is common and feeding results in localized necrosis on the seeds, seed spotting, deformation, and shriveling (Khaemba & Mutinga, 1982). Two other pentatomids, Callidea dregei Germar and C. bohemani (Stal), also attack sunflower during the seed-filling stage (Hill, 1975; Khaemba & Mutinga, 1982). Another serious pest of developing sunflower seeds is Nysius stali Evans (Lygaeidae). In Nigeria, it first occurs on sunflower during the bud stage but becomes most numerous during seed filling (Misari, 1990).

INSECT PESTS OF WESTERN EUROPE

Insect pest problems are of less concern in the sunflower production areas of western compared to eastern Europe. Rajamohan (1976) in his extensive bib• liography of sunflower pests noted that both Lygus sp. (Miridae) and the aphid, Brachycaudus helichrysi Kaltenbach, attacked sunflower foliage in Germany. SUNFLOWER INSECTS 215

Muhle (1953) mentioned that in Germany the leafhopper, Aphrodes bicinctus Schrank (Homoptera: Cicadellidae), fed in sunflower buds. The review of pests of oil-producing plants by Flachs (1936) mentioned the following insects as pests of sunflower in Germany: Aphis fabae Scop. (Homoptera: Aphidae); Lygus pratensis L. (Hemiptera: Miridae); Dolycoris baccarum (L.) (Hemiptera: Pentatomidae); Gstrinia nubilalis (Hubner) and Phlyctaenodes sticticollis (L.) (Lepidoptera: Pyralidae), and Phytomyza geniculata Macq. (Diptera: Agromyzidae ). Insects recorded as pests of sunflower in Italy include Lygus spp. (Viggiani & Jesu, 1985), Acanthiophilus helianthi (Rossi) (Diptera: Tephritidae), which feeds on the immature seeds (Belcari, 1985), and Eurydema ventrale Kolenati (Hemiptera: Pentatomidae), whose nymphs attack the flowers (Ciampolini et aI., 1986). Bagnoli (1975) studied the insects associated with sunflower heads includ• ing pests, pollinators, and beneficial species. Anthocorids (Hemiptera) were the most numerous species on the heads. The European sunflower moth, Homoeosoma nebulellum Denis and Schiffermuller, has been an important pest in many parts of Europe since the cul• tivation of sunflower began in 1860 (Kiewnick, 1964). Damage by the European sunflower moth to late-season sunflower plantings was reported in 1983 from southern France. Larvae of the moth have been noted to develop in the flowers of Silybum marianum L. or Sececio jacobea L. (ragwort) (Zagatti et aI., 1991). Zagattii et al. (1991) isolated the sex pheromone of the moth as a monitoring tool since the moth is considered a potentially serious pest in the sunflower produc• tion areas of France. Gpatum sabulosum L. (Coleoptera: Tenebrionidae) was found to attack and feed on the cotyledon and root of seedling sunflower (d'Aguilar & Pacquetian, 1963). Badenhausser et al. (1988) showed that in west• central France infestations of Lygus spp. (chiefly L. pratensis L. and L. rugulipen• nis Poppius) (Miridae) and an aphid, B. helichrysi, can reduce sunflower yields. Additional pests of sunflower described by Hariot (1986) included the aphid, A. fabae, the leafhoppers, Empoasca pteridis Dhlb. and Eupteryx atropunctata Goeze (Cicidellidae), and a leafminer, Phytomyza horticola Goureau. Ballanger et al. (1985) presented an extensive list of over 20 pests found to occur on culti• vated sunflower in France. They also included natural enemies attacking the pests.

INSECT PESTS OF CENTRAL AND EASTERN EUROPE

Approximately 240 species of insects attack sunflower in the five major sunflower producing countries of Yugoslavia, Hungary, Bulgaria, Romania, and the former USSR where sunflower production totals about 6 million hectares (Maric et aI., 1988). Previous reviews of sunflower insect pests include: Yugoslavia (Camprag & Sekulic, 1987; Maric et aI., 1988), Hungary (Bujaki, 1984; Koczka, 1985), Bulgaria (Shindrova & Kontev, 1982), Romania (Paulian & Tiinase, 1974), and the former USSR (Dekhtiarev, 1929; Arkhangelskii & Romanova, 1930). 216 CHARLET ET AL.

STEM AND ROOT FEEDERS

Acheta deserta Pall. [Orthoptera: GryUidae]

Acheta deserta frequently occurs in cultivated soil of plains and moist low• lands and is a major sunflower pest in Yugoslavia, Hungary, Romania, Bulgaria, and the former USSR (Maric et aI., 1988).

Description and Life History Acheta deserta has one generation per year and overwinters as a nymph. The nymphs are brown and darken to black at maturity. The adult is 18 mm long and black. Eggs are laid at the end of spring in moist, loose soil and nymphs are present at the end of June. Rainy years, warm weather, winters with snow cover, crop irrigation, weedy fields, and the presence of large clods in the fields are con• ducive to the buildup of high populations of crickets. Both maize and sugarbeet (Beta vulgaris L.), favor the increase in populations of this pest (Bujaki & Manhertz, 1986; Maric et aI., 1988).

Damage Acheta deserta is polyphagous and both the nymphs and adults damage sunflower. Tobacco (Nicotiana tabacum L.), sugarbeet, bean (Phaseolus spp.), and melons also are hosts. They damage sunflower seedlings, especially at the cotyledon stage. Large populations attacking at the cotyledon stage may devas• tate large areas of sunflower. Individuals can destroy 40% of the cotyledon tissue. Yearly damage in Yugoslavia from 1963 to 1973 was between 5 to 10% (Maric et aI., 1988).

Management Strategies Effective management techniques include soil tillage, crop rotation, and weed control. Sunflower should not be grown after sugarbeet or maize (Bujaki & Manhertz, 1986). Insecticides also have been effective in reducing damage caused by these pests. The economic threshold in young crops is 0.5 to 2 adults/m2 (Maric et aI., 1988).

Lethrus apterus Laxm. [Coleoptera: Scarabaeidae]

Lethrus apterus occurs in dry, uncultivated soils and is common on plains, pastures, or sideroads. It is a major sunflower pest in southeastern Europe, espe• cially in Bulgaria and the former USSR (Dekhtiarev, 1929; Maric et aI., 1988).

Description and Life History Lethrus apterus adults are 20 mm long, wingless, and black, with well• developed jaws (Dekhtiarev, 1929; Maric et aI., 1988). It overwinters as an adult and emerges at the beginning of spring in mid-April. Burrows up to 75 cm long SUNFLOWER INSECTS 217 are constructed in the soil and provisioned with plant parts cut from the nearby crop. Eggs are laid in the subsoil burrows among the plant material. Larvae remain in the burrows and development is rapid with pupation occurring by the end of June. The development from egg to adult requires 45 to 50 d. There is one generation per year.

Damage The adult stage is polyphagous, feeding on different weed species and cul• tivated crops, especially sunflower (larvae feed on plant parts placed in subsoil tunnels by the adults) (Dekhtiarev, 1929; Maric et aI., 1988). At the end of April and early May, adults attack the top ofthe stems and feed on leaves of young sun• flower plants. Plant parts are carried to the subsoil burrows. The greatest damage occurs at borders of sunflower fields, especially if adjacent fields are uncultivat• ed or roadsides are weedy. Empty spots in the field indicate attack by L. apterus and high scarab populations may completely destroy fields of young sunflower plants.

Management Stategies The most important control measures are cultural: weed removal, plowing edge rows, and interrow cultivation of row crops to help destroy L. apterus devel• opment sites (Dekhtiarev, 1929; Maric et aI., 1988).

Wireworms [Coleoptera: Elateridae]

The most destructive wireworms are species in the genus Agriotes (espe• cially A. ustulatus Schall., A. sputator L., A. gurgistanus Fald, A. ponticus Stepanov, A. lineatus L., and A. obscurus L.). Species in the genera Selatosomus and Melanotus (including M Jusciceps Gryll.) and Athous haemorrhoidalis Fabricius also have caused damage to sunflower in central and eastern Europe (Arkhangelskii & Romanova, 1930; Kabanov, 1969; Paulian & Tiinase, 1974; Barteneva, 1976; Maric et aI., 1988).

Description and Life History Wireworm larvae are straw-yellow to reddish in color and at maturity are 25 mm long (Kabanov, 1969; Maric et aI., 1988). Female wireworms move to fields of small grains, alfalfa (Medicago sativa L.), and clover (Trifolium spp.), to lay eggs in the soil. Eggs are milky-white and about 0.8 mm long. Larvae live underground and move vertically and horizontally through the soil. Depending on conditions, larvae may need 3 to 5 yr to complete development and develop through 13 to 14 instars. Moist soil, growing small grains, alfalfa, and clover on large areas, the absence of mechanical soil tillage, crop irrigation, and the pres• ence of widely spread weeds are conducive to population buildup of wireworms. Wireworms overwinter in both the larval and adult stages. 218 CHARLET ET AL.

Damage Larvae are polyphagous and will damage seeds, seedlings, and young plants. They attack the underground plant parts and cotyledons before seedling emergence. Plants from germination to the occurrence of the first few pairs of leaves sustain the greatest damage. At high larval densities, even plants with three to four pairs of leaves may be destroyed, especially during drought condi• tions. If severely attacked, the sunflower canopy is reduced (the occurrence of blank areas in the field is often due to attack by wireworms) or destroyed, requir• ing replanting. Larval densities in sunflower production areas increased from about 2 larvae/m2 in the early 1960s to averages over 6 larvae/m2 in the early 1980s in spite of insecticidal control (Maric et aI., 1988). Population levels as high as 12 to 141arvae/m2 have occurred in the former USSR. This larval densi• ty completely destroys the field. Under favorable conditions of high moisture and weed cover, levels of 2 larvae/m2 can cause as much damage as normally sus• tained from 5 larvae/m2 (Barteneva, 1976).

Management Strategies Natural enemies of wireworms include predators of the family Carabidae and numerous predatory birds. Cultural control measures include crop rotation, soil tillage, fertilization, and weed removal. Chemical control includes both foliar and systemic insecticides (Barteneva, 1976). The economic threshold is 2 lar• vae/m2 (Maric et aI., 1988).

Psalidium maxillosum Fabricius [Coleoptera: Curculionidae]

Psalidium maxillosum occurs in central and southeastern Europe, especial• ly in the Steppe areas. It is a major pest of sunflower in Yugoslavia, Hungary, Bulgaria, and the former USSR (Shchegolev, 1928; Paulian & Tiinase, 1974; Djurkic et aI., 1976; Maric et aI., 1988).

Description and Life History The adult weevil is 6 to 10 mm and shiny-black. The pest overwinters in both the adult and larval stages. New adults appear in the spring and live about 2 yr. They inhabit the high, dry and warm parts of the field. Larvae live in the soil. Loose soil, dry and warm spring conditions, and large areas under row crops (sunflower, sugarbeet, etc.) are favorable for the development of high populations of this pest. One generation requires 2 yr (Maric et aI., 1988).

Damage The polyphagous adult is especially harmful to sunflower and sugarbeet. During colder weather, the insects damage the underground portion of young sun• flower plants. Plants are most susceptible when germinating and during emer- SUNFLOWER INSECTS 219 gence of young cotyledons, especially during periods when plant growth is retarded. Psalidium maxillosum consumes cotyledons and often leaves only bare stems. Severe attack by P maxillosum may destroy the whole sunflower field (Maric et aI., 1988).

Management Strategies Natural enemies of P maxillosum include different species birds, frogs, lizards, and entomophagous fungi (Maric et aI., 1988). Cultural control measures that accelerate growth of sunflower during the crucial period from germination to the occurrence of the first pairs of leaves aid in reducing damage from this pest. Irrigation of crops also has a negative effect on the weevil. The economic thresh• old is 2 to 5 adults/m2 at the cotyledon stage. Adults cannot fly and can be pre• vented from spreading from the neighboring fields by digging a trench and treat• ing with insecticides. Foliar applications also can be used to control P maxillo• sum.

Tanymecus dilaticollis Gyllenhal[Coleoptera: Curculionidae)

Tanymecus dilaticollis frequently occurs in the arid and semiarid Steppe plains of southeastern Europe and Asia Minor. The pest is active in maize grow• ing areas with chernozem soils. Tanymecus dilaticollis is a sunflower pest in Yugoslavia, Bulgaria, Romania, Hungary, and the former USSR (Paulian & Tiinase, 1974; Camprag & Sekulic, 1987; Maric et aI., 1988; Saringer & Takacs, 1994).

Description and Life History The adult is gray, 7 mm long, and overwinters in the soil under maize (Maric et aI., 1988). Adults are most numerous in April and May. Females lay the highest number of eggs in May in soil planted to different crops, especially maize. Larvae live in the soil. Warm and dry springs, large areas under maize cul• tivation (especially maize monoculture), and chernozem, alluvial, and sandy soils are favorable to the development of high densities of T dilaticollis. There is one generation per year (Maric et aI., 1988; Saringer & Takacs, 1994).

Damage The polyphagous adult usually feeds on maize. Although maize is a com• mon host, sunflower, sorghum, sugarbeet, and tobacco also are attacked. The pest feeds on the seed in the soil, cotyledons of the emerged plant, stem, and leaves. Only the adult stage is harmful to sunflower, especially from germination and sprouting to the formation of the first few pairs of leaves. Development of high populations of T dilaticollis, especially when maize is grown prior to sunflower, may result in the destruction of entire sunflower fields. This weevil is present in about 65% of sunflower fields in Yugoslavia (Maric et aI., 1988; Saringer & Takacs, 1994). 220 CHARLET ET AL.

Management Strategies Natural enemies are ineffective in reducing damage from T. dilaticollis. The use of certain cultural control methods have been more important in reduc• ing losses. Crop rotation, which excludes maize growing on a single field for two or more succeeding years, has been an effective technique in preventing damage. Sunflower should be planted after growing less susceptible crops (small grains) and should not be grown after sugarbeet or maize (Bujaki & Manhertz, 1986). Irrigation significantly reduces the number of older larvae and cocoons. Chemical control includes both foliar and in-furrow treatment with systemic insecticides at planting (Maric et aI., 1988; Saringer & Takacs, 1994).

Agrotis segetum Denis and Schiffermiiller [Lepidoptera: Noctuidae]

Agrotis segetum is a major cutworm pest of sunflower. It is found in Yugoslavia, Hungary, the former USSR, and other countries in southeastern Europe (Shchegolev, 1928; Camprag & Sekulic, 1987; Maric et aI., 1988).

Description and Life History Mature larvae of A. segetum are gray-brown and about 40 mm long (Maric et aI., 1988). There are two generations per year with the cutworm overwintering as a mature larva in the soil. Larvae pupate in April and adults are present at the end of May and the beginning of June. Females lay eggs on different row crops and young alfalfa, especially when fields are weedy. The first-generation larvae are present from June to the middle of July and succeeding generations from the end of August. A warm, dry spring and summer; a long, warm, and moderately moist autumn; and the presence of weeds are conducive for build-up oflarge pop• ulations of this sunflower pest.

Damage Larvae are polyphagous stem feeders. Injury by the last three instars results in the highest losses and characteristic empty spots in the field. Entire fields may be lost. First generation larvae are harmful to sunflower, especially to late-plant• ed and weedy fields, but the second generation seldom causes damage to sun• flower (Dekhtiarev, 1929; Maric et aI., 1988).

Management Strategies Natural enemies include parasitoids, predators (including different species of birds, frogs, lizards, and moles), enthomophagous fungi, bacteria, and virus diseases (Dekhtiarev, 1929; Maric et aI., 1988). Management methods that include early planting, weed control, and soil tillage are effective in preventing damage from cutworms. The presence of two to three 2nd- or 3rd-instar larvae/m2 is considered the economic threshold. Chemical control of cutworms includes foliar treatment and poison baits. SUNFLOWER INSECTS 221

Euxoa temera Hubner [Lepidoptera: Noctuidae]

Euxoa temera is a Mediterranean-Asian species and is a harmful pest in numerous crops. This cutworm is a major sunflower pest in Yugoslavia, Hungary, Bulgaria, and Romania (Camprag & Sekulic, 1987; Maric et aI., 1988).

Description and Life History Adult moths are light to dark-brown (Maric et aI., 1988). Mature larvae are brownish-gray and 35 to 45 mm long. The moth is univoltine and overwinters in the egg stage. Eggs hatch in March and larval development is completed by the end of May. The larvae then spend 8 wk (2 mos) in diapause. Moths are present in August and September with eggs laid in alfalfa, weedy fallow soil, and winter crops. Several successive warm and dry years are conducive to the buildup of large populations of E. temera. The pest is most common in crops grown in hydromorphic black soils, smonitza soils, as well as alluvial soils.

Damage Larvae are polyphagous and are most damaging to sunflower, alfalfa, sug• arbeet, and other row crops. Damage resembles that of A. segetum. Mature larvae attack germinating plants after migrating from alfalfa and neighboring row crops. In two to three nights, large areas of the field may be damaged (Maric et aI., 1988).

Management Strategies Natural enemies include enthomophagous fungi and parasitoids, including species of the egg parasitoid, Trichogramma (Maric et a!., 1988). Early planting of sunflower seed, weed eradication, and soil tillage contribute to the control of this pest. Weeds should be eradicated in August, during the mass flights of moths, since they are preferred oviposition sites. Deep plowing, beginning in the middle of September, effectively destroys eggs. Chemical control is similar to that used for A. segetum. The economic threshold in sunflower is 0.1 to 0.5 larvae/m2, depending on the plant growth stage at the time of attack.

Miscellaneous Coleoptera [Cerambycidae, Mordellidae]

A cerambycid pest of sunflower stems, Agapanthia dahli Richt., was reported to cause serious damage to sunflower in the former USSR in the 1920s (Shchegolev, 1928; Dekhtiarev, 1929; Arkhangelskii & Romanova, 1930; Dogrowolsky, 1930). It also has been found attacking sunflower in Hungary, although it was previously known only from composite weed hosts (Horvath & Nemeth, 1987-1988; Horvath & Bujaki, 1988). The larvae overwinter in sun• flower stems and emerge as adults in June. Larvae feed within the stem, con• suming the pith. Usually there is only one larva per stem. Attacked plants are stressed and yield is reduced (Dekhtiarev, 1929; Arkhange1skii & Romanova, 1930). 222 CHARLET ET AL.

The mordellid, Mordellistena parvula Gyllenhal, was reported to be the most common and serious pest of sunflower in the former USSR in the late 1920s. Larvae tunneled in the sunflower stems destroying the vascular tissue and reducing plant vigor. Mordellistena parvula overwinters in sunflower stems. This pest also was noted to have some connection with the spread of Sclerotinia sclerotiorum (Lib.) de Bary in sunflower plants (Dekhtiarev, 1929; Arkhangelskii & Romanova, 1930).

FOLIAGE FEEDERS

Brachycaudus helichrysi Kaltenbach [Homoptera: Aphididae]

The aphid, Brachycaudus helichrysi, is worldwide in distribution. It attacks sunflower in western Europe and also is a major pest of sunflower in Yugoslavia, Hungary, Romania, Bulgaria, and the former USSR. It often attacks sunflower crops in association with Aphis fabae Scop. (Bujaki, 1984; Camprag et aI., 1988b; Thalji, 1992).

Description and Life History The aphid, a migratory species, overwinters in the egg stage on species of the genus Prunus. Alate forms of the second or third generation migrate from Prunus to secondary hosts. Sunflower becomes infested in the first half of May and high numbers of aphids occur in June. Plants may be attacked from the two• to four-leaf stage to harvest (Bujaki, 1984). At the beginning of autumn, aphids return to the primary host, where they lay overwintering eggs in October. The application of high doses of nitrogen fertilizers favors population increases of this pest (Bujaki, 1984; Camprag et aI., 1988b; Maric et aI., 1988).

Damage Aphid colonies continuously infest the upper leaves of sunflower. The pest usually abandons the older leaves to infest the newer leaves. The aphid general• ly inhabits the lower surface of the leaf, feeding on sap in the central and lateral veins. The feeding causes chlorotic spots on the leaves and the upward curling of several top leaves, which deteriorates plant growth (Color Plate 33). The aphid also may attack the buds and disk flowers on the head. Damage appears earlier and is more severe on field margins (50-100 m from edge) than in centers of sun• flower fields (Bujaki, 1984). Populations of625 aphids/plant have been shown to reduce sunflower yield by as much as 16%. There is a positive correlation between the presence of aphids and occurrence of diseases caused by Botrytis and Sclerotinia (Maric et aI., 1988). Early planted sunflower fields sustain the greatest damage from aphid attack (Camprag, 1976).

Management Strategies Predatory Syrphidae, Chrysopidae, and especially Coccinellidae are the major enemies of aphids (Thalji, 1988). One ladybird beetle may destroy about SUNFLOWER INSECTS 223

600 aphids (Camprag et aI., 1988b; Maric et aI., 1988). Thalji (1992) studied the dynamics of predaceous Diptera in sunflower and found that the Syrphidae were the most important. Eupeodes corollae Fabricius represented more than 80% of the individuals attacking the aphids. Members of the families Cecidomyiidae and Chamaemyiidae also attacked B. helichrysi (Thalji, 1992). Management of aphids includes the use of resistant hybrids, chemical control, and cultural control. Sunflower should not be planted before the optimum sowing dates, the rate of nitrogen fertilizer should be carefully monitored, and weeds should be controlled. Chemicals with low toxicity to predators and parasitoids should be used. Insecticides should be applied when 20 to 30% of plants on the edges of large fields are attacked and favorable weather conditions for the spreading of pest are expected. Only the plants within 50 m of the field margin should be treated (Bujaki, 1984; Maric et aI., 1988).

Beet Webworm, Loxostege sticticalis (L.) [Lepidoptera: Pyralidae]

The beet webworm is a migratory species that frequently occurs in central and southeastern Europe, where it has been a serious pest of cultivated crops. It is a major sunflower pest in the former USSR, Yugoslavia, Hungary, Romania, and Bulgaria. The beet webworm caused extensive damage to sunflower in the former USSR between 1900 and 1930 and again beginning in the 1970s. The for• mer USSR seems to be the center of migration for this species (Knor & Tibatina, 1978; Maric et aI. , 1988).

Description and Life History The adult webworm is gray-brown (Maric et aI., 1988). The caterpillars are greenish-gray with the first instars 2 mm long and mature larvae about 20 mm. Mature larvae overwinter in the soil. The first generation begins in late Mayor early June. Adults sometimes use wind currents to fly over several hundred kilo• meters. Females often lay eggs on young weeds in fields of a variety of different crops. Abundant rainfall and warm weather are favorable for reproduction of the beet webworm. There are two to three generations per year. This species has a cyclical damaging pattern of a few to 10 yr or even several decades.

Damage The caterpillars are extremely polyphagous and damage both vegetative and reproductive plant parts. The greatest amount of damage has been observed in sunflower, alfalfa, red clover (Trifolium pratense L.), sugarbeet, maize, hemp (Cannabis sativa L.), and cotton (Gossypium spp.). Mature larvae often migrate in high numbers from field to field in search of food. They damage leaves, stems, flowers, and heads of sunflower. They feed on leaves, so that during a severe attack only the stems remain. In 1975, over 100 000 ha were treated in the former USSR and extensive damage occurred in Yugoslavia. Yields were reported to be reduced by over 50% in some areas of Romania, Hungary, and Bulgaria in 1975 (Arkhangelskii & Romanova, 1930; Maric et aI., 1988). 224 CHARLET ET AL.

Management Strategies Natural enemies (parasitoids, predators, and diseases) are significant mor• tality factors of the beet webworm. Weed destruction, deep soil tillage, and early planting of sunflower are important cultural control methods. Alfalfa is often the center of activity for this pest, from which it moves into sunflower and other crops. Alfalfa should be mowed prior to the mass movement of caterpillars. Insecticidal control includes both chemicals and the use of Bacillus thuringiensis. The economic threshold is five larvae per plant (Maric et aI., 1988).

Mamestra brassicae L [Lepidoptera: Noctuidae]

Mamestra brassicae feeds on sunflower in Yugoslavia, Romania, the for• mer USSR, and other countries of southeastern Europe (Shchegolev, 1928; Dekhtiarev, 1929; Maric et aI., 1988).

Description and Life History Young larvae of Mamestra brassicae are green and mature stages are gray or dark-green, light or dark-brown, and about 40 to 45 mm long. The moth is bivoltine and overwinters in the pupal stage. Moth flight occurs in May and June and the second generation begins at the end of July and in August. Females lay eggs on the leaves of different plants, especially on cabbage (Brassica oleracea L.), pea (Leguminosae), and beet (Beta vulgaris L.). High rainfall and crop irri• gation are favorable for the multiplication of this pest (Maric et aI., 1988).

Damage The second generation is much more numerous and damaging than the first generation. The polyphagous larvae attack plants in August and the first half of September. They damage the leaves and may consume all but the sunflower stem (Arkhangelskii & Romanova, 1930). During its development, a single caterpillar may eat an average of 170 cm2 or 4 g of sunflower leaves (Maric et aI., 1988).

Management Strategies Trichogramma egg parasitoids are major natural enemies of M brassicae. Deep fall plowing reduces the number of overwintering pupal cocoons. Chemical insecticides also are used to control this pest (Maric et aI., 1988).

CAPITULUM FEEDERS

Lygus rugulipennis Poppius [Hemiptera: Miridae]

Lygus bugs, especially L. rugulipennis, are significant sunflower pests in Yugoslavia, Hungary, Bulgaria, and Romania (Shindrova & Kontev, 1982; Koczka, 1985; Camprag et aI., 1988a; Maric et aI., 1988). Other important species include the alfalfa plant bug, Adelphocoris lineolatus (Goeze), a pest that SUNFLOWER INSECTS 225 also occurs in North America, L. pratensis (L.), and L. gemelatus H.S. (Camprag et ai., 1986b, 1988a). In the former USSR, the main mirid pest species is L. pratensis (Piven, 1976).

Description and Life History Lygus rugulipennis has two or three generations per year (Koczka, 1985; Camprag et ai., 1986b; Maric et ai., 1988). The adult overwinters in crop residue in plowed and unplowed fields. In spring, the adults move into a variety of weed species or alfalfa. The adults are extremely mobile and may migrate I to 2 km or more to new crops after alfalfa or grass is cut, especially during dry springs. They begin feeding on sunflower at the end of May. Populations peak in July and August, from flowering through maturation of sunflower. The second generation feeds and develops on the sunflower head. Dry and warm weather, as well as the presence of weeds, are favorable for the development of high densities of L. rugulipennis.

Damage Lygus rugulipennis, a polyphagous species, feeds on numerous crops and weeds. Eggs are laid in the stem, leaf petioles, and sunflower heads. Nymphal and adult feeding damages these organs, as well as buds, disk flowers, and seed. Use of susceptible hybrids, warm and dry weather, lack of weed control, and the presence of alfalfa and clover (Trifolium spp.) increase the degree of damage caused by L. rugulipennis (Camprag et ai., 1986b; Maric et aI., 1988). Crops are most susceptible to severe damage at flowering. Attack by L. rugu/ipennis decreases seed weight (13-52%), oil content (50-190 g/kg), and seed viability (20%) (Bujaki & Biro, 1986; Camprag et aI., 1986a; Camprag et aI., 1988a; Maric et aI., 1988). Damage by L. rugu/ipennis enhances the infection of the head and seeds by Botrytis cinerea Pers., Alternaria spp., Fusarium spp., and Sclerotinia sclerotiorum (Bujaki & Biro, 1986; Maric et aI., 1988).

Management Strategies Natural enemies include egg parasitoids, predators, and fungal diseases. Management methods include deep soil tillage, use of quality seed, resistant hybrids, optimum density of plant canopy, weed control, and isolation of sun• flower from alfalfa, clover (Trifolium spp.), and grasses. Insecticides are applied when 4 to 5 Lygus are present at the bud stage or 10 at flowering (Piven, 1976; Bujaki, 1986; Maric et ai., 1988).

Miscellaneous Plant Bugs [Pentatomidae, Lygaeidae, Coreidae]

Over 20 species of plant bugs have been recorded as pests of sunflower (Shindrova & Kontev, 1982; Camprag et aI., 1988a; Maric et ai., 1988). As was the case with the Lygus species, these pests also attack the seed of sunflower reducing oil and protein content (Piven, 1976; Shindrova & Kontev, 1982; Shindrova & Ivanov, 1982; Bujaki, 1986). The bugs showed a preference for seed 226 CHARLET ET AL. on the outer margins of sunflower heads (Shindrova, 1982). Species recorded as pests include: Dolycoris baccarum (L.), Palomena prasina (L.), Graphosoma italicum (Muller), and Holcostethus vernalis (Wolff) (Pentatomidae), Lygaeus equistris L. (Lygaeidae), Coreus marginatus L, and Corizus hyosciami L. (Coreidae) (Shindrova, 1982; Shindrova & Kontev, 1982; Camprag et aI., 1988a; Maric et aI., 1988; Zatyamina et aI., 1988; Bujaki & Horvath, 1992). Some resis• tance in certain sunflower lines has been reported (Shindrova, 1982).

Helicoverpa armigera (Hubner) [Lepidoptera: Noctuidae]

Helicoverpa armigera is a major pest of sunflower in the former USSR and also occurs in other countries of southeastern Europe (Maric et aI., 1988).

Description and Life History Adult body color is variable, from light-green to yellow or red-brown. Adult moths are about 40 mm in length. There are two to three generations per year. Helicoverpa armigera overwinters in the pupal stage. Eggs are laid mainly on flowers of plants. High temperatures and wet springs, as well as warm sum• mers, provide favorable conditions for development of high populations of H. armigera (Maric et aI., 1988).

Damage Larvae are polyphagous and attack the flowers of numerous crops. Larvae feed on the receptacle and under heavy infestation cause damage so severe that the seed falls from the head. The caterpillars also feed on sunflower seed after heads mature (Maric et aI., 1988).

Management Strategies Species of the egg parasitoid, Trichogramma, are major natural enemies of H. armigera. Soil tillage, insecticides, and the application of K to the soil aid in the control of H. armigera (Maric et aI., 1988). Larvae also are attacked by the braconid parasitoid, Habrobracon hebetor Say (Horvath & Bujaki, 1992).

European Sunflower Moth, Homoeosoma nebulellum Denis and Schiffermuller [Lepidoptera: Pyralidae]

The European sunflower moth is a common species in Hungary, Yugoslavia, Romania, Bulgaria, and the former USSR. The moth was first noted as a pest in the late 1860s and was widely dispersed throughout the region by the early 1900s (Reh, 1919; Shchegolev, 1928; Kiewnick, 1964). Large yield reduc• tions occurred in the former USSR between 1895 to 1897 and in 1917, over one• third of the sunflower crop in Romania was destroyed (Maric et aI., 1988). SUNFLOWER INSECTS 227

Description and Life History The adults are a light-gray, 11 to 12 mm long with leading edges of wings white underneath and two dark spots in the center of the wing. Hind wings are transparent and whitish with gray edges. Overall body color is a dirty-yellow. Larvae are a dirty green-yellow with dark stripes on the back and two stripes on each side. The moth usually has two generations per year and overwinters as a mature larva in a cocoon about 3 cm below the soil surface (Dekhtiarev, 1929; Maric et aI., 1988). Reh (1919) reported that there were probably three genera• tions in Romania. A third generation has been detected in Hungary (Horvath & Bujaki, 1992). The first generation develops mainly on wild Compositae. Females of the second generation lay eggs on the inner wall of the ring of coa• lesced stamens of early bloom sunflower. The first two larval instars feed only on pollen and the last three on the seeds. Larvae also may feed on the receptacle itself (Dekhtiarev, 1929; Horvath & Bujaki, 1992).

Damage Damage caused by the European sunflower moth is similar to that caused by the other species of Homoeosoma occurring in North and South America. Larvae construct webbing over the damaged inflorescence, similar to H. eleetel• lum, giving the head a trashy appearance (Color Plate 34). A single larva may destroy up to 10 mature seeds (Maric et aI., 1988). A total of 100 or more larvae have been known from a single head (Dekhtiarev, 1929). There is a positive cor• relation between the presence of larvae and the diseases caused by Botrytis and Sclerotinia (Maric et aI., 1988; Horvath & Bujaki, 1992).

Management Strategies Plant resistance is used to reduce damage from the European sunflower moth. Cultivars with high levels of phytomelanin in the seed confer resistance by reduced larval feeding (Kiewnick, 1964; Maric et aI., 1988). Early planted sun• flower in Hungary sustained less feeding damage since the plants are at a stage that is less susceptible to attack from the second and partial third generations of the moth (Horvath & Bujaki, 1992). The European sunflower moth also is attacked by a complex of parasitoids. Sakharov (1925) reported that larvae were attacked by ichneumonid paras ito ids (Crematus ornatus var. variegatus Szepl. and Exoehus sp.), two chalcids, a braconid parasitoid, a fungus, and the predator Chrysopa perla L. Horvath and Bujaki (1992) noted that earlier Russian literature also included Exeristes roborator (Fabricius) (Ichneumonidae) and Apanteles sp. (Braconidae) as enemies of the moth. They studied the biology of Habrobracon hebetor Say (Braconidae) in Hungary and found that the adults appear in late March to early April, the parasitization rate in second generation larvae was 90% but decreased to 20 to 30% in third generation larvae, and that the parasitoid had about six to seven generations, with each requiring approximately 12 to 14 d (Horvath & Bujaki, 1992). The predators, Coccinella septempunctata L., Adalia bipunetata L., Nab is ferus L., and Orius spp. also contributed to the mortality of the European sunflower moth (Horvath & Bujaki, 1992). 228 CHARLET ET AL.

INSECT PESTS OF ASIA

Insect pest problems have been described from a number of countries in Asia, especially India. A new species of Tingidae (Hemiptera), Galeatus helianthi Onder and Lodos, was described from Turkey as a leaf-feeding pest of sunflower (Onder & Lodos, 1977). Parwin (1988) reported that the following insect pests accounted for sunflower losses of 5 to 7% in Iran: Homoeosoma neb• ulellum (damage to seed), Spodoptera exigua (Hubner) (defoliation), S. littoralis Boisduval (defoliation), and Agrotis segetum Schiff (stem cutting). Research on H. nebulellum in Iran revealed there are four generations annually and that para• sitism of larvae showed potential to suppress populations of the moth. Moth lar• vae were attacked by the braconid wasps, Bracon hebetor Say and Bracon sp., and an unidentified ichneumonid and pathogen (Moradeshaghi, 1974). The strawberry spider mite, Tetranychus turkestani U garov and Nikolski, also has become a pest of sunflower in Iran. N avvab-Gojrati and Zare (1978b) found some tolerance in the 15 different cultivars of sunflower screened against the mite. Several acaricides were effective in suppressing damaging populations of the mite in southern Iran (Navvab-Gojrati & Zare, 1978a). The western flower thrips, Frankliniella occidentalis (Pergande), caused severe damage to sunflower in Israel in 1992 and 1993. Damage to the seed was greatest on the margins of the sunflower head. Later plantings were noted to have less damage probably due to the action of predators, especially Orius spp. (Chyzik et aI., 1995). A survey of sunflower insect pests in the Philippines revealed a total of 11 insects attacking the foliage, stems, and heads. The most damaging species were Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), which damages the head and seeds, and Ostrinia damoalis Walker (Lepidoptera: Pyralidae), which feeds in the stem resulting in stalk breakage (Lopez et aI., 1979). Sunflower has become an important oilseed crop in China, and 94 insects representing 7 orders and 28 families have been reported as pests of the crop (Li & Zhang, 1988). The European sunflower moth, H. nebulellum, is one of the important pests in Heilongjiang Province (Yeh & Chu, 1965), Xinjiang Province, Jilin Province, and Inner Mongolia (Zhou et aI., 1988). Damaging infestations by the moth occurred after the late 1960s with 5 to 10% seed damage. Studies on the moth in Jilin Province showed one to two generations per year, with the first gen• eration infesting sunflower. Thus, later plantings had fewer damaged seeds. Screening of germplasm isolated cultivars with resistance to the moth and prompted the recommendation that this was the best method to control the moth (Zhou et aI., 1988). Over 50 species of insects attack sunflower in the production areas ofIndia and Pakistan (Lewin, et aI., 1973; Sandhu et aI., 1973; Rajamohan, 1976; Sattar et aI., 1984). The crop is grown during two to three seasons depending on the location, and although many pests cause damage during only one seasons, some attack all the sunflower plantings. The major insect problems are caused by defo• liating species. Hassan et aI. (1984) remarked that about 18 insects were pests of sunflower at Faisalabad, Pakistan, during the two growing seasons. The most important SUNFLOVVERINSECTS 229 pests in the spring vvere the aphids, Myzus persicae (Sulzer) and Rhopalosiphum erysemi (Kaltenbach), and the moths, Cirphis unipuncta Haw. and Plusia spp. (N octuidae). In the autumn, leaves are attacked by Empoasca devastans (Dist.), and buds and heads by Helicoverpa spp. (Hassan et aI., 1984). Heliocoverpa armigera also was reported to cause damage to sunflower foliage (Channa et aI., 1993). Sattar et a1. (1984) described damage by nine species of insect pests in Pakistan. These included aphids, whiteflies (Bemisia tabaci (Gennadius)), grasshoppers, Carpophilus sp. (Nitidulidae), and Disonycha sp. (Chrysomelidae), in addition to E. devastans and H. armigera. The arctiid moth, Spilosoma casignetum (Kollar), can cause severe defoli• ation of sunflower in India (Banerjee & Haque, 1983). Larvae feed on climbing hempweed (Mikania cordata Burm.) when sunflower is not present (Banerjee & Haque, 1985). Another arctiid that is an important defoliator of sunflower is S. obliqua (Walker) (Singh & Singh, 1993a,b). This pest also attacks jute (Abutilon theophrasti Medik.) and a wide variety of vegetables and field crops in India (Kabir & Miah, 1987; Singh & Singh, 1993b). Adsule and Kadam (1979) report• ed that a number of chemicals could effectively control S. obliqua on sunflower. Singh and Singh (1993a) determined that some sunflower cultivars offered resis• tance to feeding damage by larvae of S. obliqua. A number of wasps, including four species of Apanteles, attack the larvae resulting in 8 to 39% parasitism (Shetgar et aI., 1990). Leaf-feeding noctuid moths reported to be serious pests of sunflower in India include: Cirphis loreyi Dupt. (Kumar & Goel, 1985), Spodoptera fitura (Fabricius) (Kumar et aI., 1992), and Plusia orichalcea Fabricius (Goel & Kumar, 1987; Kumar & Goel, 1989). Another insect that feeds on sunflower leaves in India is the tingid bug, Galeatus scrophicus (Saunders) (Sing et aI., 1991). Both the nymphs and adults suck sap from the leaves, stem, and bracts of the sunflower head, which results in a yellowing of the tissue (Verma et aI., 1974). The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae), also causes serious damage to sunflower leaves (Sethi et aI., 1978; Balasubramanian & Chelliah, 1985). Populations of the whitefly develop on adjacent crops, such as cotton, and then move into the sunflower field (Diraviam & Uthamasamy, 1992). Populations of the leafhopper (Homoptera: Cicadellidae), Amrasca biguttula biguttula (Ishida), increase during the growing season and can cause serious damage to sunflower foliage (Brar & Sandhu, 1974; Sethi et aI., 1978; Mahto, 1990). The aphid, Aphis gossypii Glover, also was included among the most damaging pests of sunflower foliage (Sethi et aI., 1978; Goel & Kumar, 1990). Goel and Kumar (1990) listed a number of predators attacking aphids in sunflower. The leaf miner, Phytomyza atricornis (Meigen) (Diptera: Agromyzidae) also is a serious pest of sunflower leaves (Rohilla et aI., 1978; Sethi et aI., 1978). Grasshoppers also have been noted to cause damage (Ayyanna et aI., 1978; Rohilla et aI., 1978; Goel & Kumar, 1989). Helicoverpa armigera causes direct losses to sunflower seeds and is an important pest of sunflower in India (Rabindra et aI., 1986; Bhosale et aI., 1990). Patel and Talati (1987) reported over 60% of heads damaged by H. armigera lar• vae and Rangarajan et al. (1977) noted that over 50% of seeds may be destroyed, followed by invasion of saprophytic fungi. Patel and Talati (1987) identified two 230 CHARLET ET AL. larval parasitoids that were responsible for 25% parasitism in the field. Chemical control of the moth has been successful (Panchabhavi et ai., 1977; Bhosale et ai., 1990) and the use of a nuclear polyhedrosis virus has been effective in reducing populations of larvae and reducing feeding losses in sunflower (Rabindra et ai., 1986). Plant bugs known to attack heads, as well as foliage, include Dolycoris indicus Stal; Nezara virudula (1.); Aphanus sordidus Fabricius; Dalpada pilicor• nis Stoll; and Eusarcocoris guttiger Thunberg (Lewin et ai., 1973; Rangarajan et ai., 1977; Sethi et ai., 1979).

INSECT PESTS OF AUSTRALIA STEM AND ROOT FEEDING SPECIES

Black Scarab Beetles, Pseudoheteronyx spp. [Coleoptera: Scarabaeidae]

At least two species of Pseudoheteronyx attack sunflower in Australia. One of them-an undescribed species with the common name of black sunflower scarab-has long been a minor problem on the Central Highlands of Queensland (Murray & Wicks, 1990), but has caused damage to large areas of seedlings, par• ticularly in northern Queensland, in recent years (Robertson & Kettle, 1992).

Description The beetles are black, about 15 mm long and flightless (Kettle & Robertson, 1994, personal communication). Eggs are spherical about 2 to 3 mm in diameter and are laid singly in the soil. There are three larval instars. Larvae are soft-bodied with brown heads and a whitish body color. The dark gut contents of older stages are visible through the body wall, especially at the posterior end. The larvae, which are called white grubs or curl grubs, are strongly curved or c• shaped. Pupae are a yellowish color.

Life History Eggs are laid in the soil throughout summer and larvae develop on the roots of grasses and other plants over the winter. Early summer rains trigger pupation and the emergence of beetles. Severe sunflower crop damage by beetles occurs with early summer (January) plantings (Robertson & Kettle, 1992). Adult black sunflower scarabs can live for up to 48 wk (12 mo) and are capable of laying eggs whenever soil moisture is adequate. They also feed whenever green plant mater• ial is available. The increased pest status of black sunflower scarab in parts of the Central Highlands is largely due to the increased density of its highly suitable host plant, parthenium weed, Parthenium hysterophorus 1.

Damage The adult beetles are the damaging stage with seedlings and young plants up to 40 cm tall being defoliated and killed. They often feed in a line across the field. The beetles hide in the soil during the day and emerge in the late afternoon to feed (Franzmann et ai., 1992b). After about an hour of feeding around sunset, SUNFLOWER INSECTS 231 they often move back into the soil. Larvae have not been recorded damaging sun• flower although larvae of another scarab, Heteronyx rugosipennis Macleay, occa• sionally damage seedlings on the Central Highlands by feeding on the develop• ing taproot (Robertson & Kettle, 1992).

Management Strategies Control can be achieved by spraying either side of the line of feeding (Franzmann et aI., 1992b). Spraying is best carried out when the beetles are active on the soil surface. Beetles also may be controlled by application of pelleted baits (using alfalfa or a similar meal) at planting. Cracked-grain baits will not control beetles. Reinfestation may occur on new cultivation or adjacent to native pasture. Keeping a field fallow is helpful.

False Wireworms [Coleoptera: Tenebrionidae] Both larvae and adults of false wireworms attack sunflower in Australia (Broadley, 1978) (Color Plate 35). Three principal species are involved: the stri• ate false wireworm, Pterohelaeus alternatus Pascoe, the eastern false wireworm, P. darlingensis Carter; and the southern false wireworm; Gonocephalum macleayi (Blackburn) (Allsopp, 1979). Another species, Celibe sp. (= Saragus sp.), is a sporadic pest in South Australia (Mowatt, 1979) and New South Wales (Forrester, 1980a).

Description Adults are black, rather nondescript beetles, which are usually found under piles of trash or low-growing weeds. Gonocephalum macleayi adults have a cov• ering of small hairs and depressions which hold soil; therefore, they tend to appear brown in red soils and gray in black soils. The adults of both genera dif• fer in general shape and in size. Gonocephalum macleayi adults are 6 to 8 mm long while Pterohelaeus are between 16 and 20 mm long (Allsopp, 1979). Eggs are laid singly into moist soil, usually under trash or low-growing weeds. Larvae are creamy, creamy-yellow, or shiny yellowish-brown in color with a thin, wire• like, tough body with three pairs of short legs directly behind the head. Larvae of G. macleayi grow to approximately 20 mm in length while those of Pterohelaeus reach about 50 mm when fully grown (Broadley & Ironside, 1980a). Fully devel• oped larvae construct earthen cells from 1 to 5 cm deep in the soil and pupate. The pupae are white and 16 to 19 mm long (Goodyer, 1983b).

Life History Adults emerge from the soil during spring and early summer. The pre• oviposition period is about 3 or 4 wk (Allsopp, 1979). Eggs hatch within 7 to 14 d and the larvae burrow down to moist soil. The larvae move as this moist layer changes with wetting and drying of the soil. Late-stage larvae are randomly dis• persed in the soil in fallow fields and in cropped fields they are found within crop rows. In fallow fields, larvae may be concentrated under areas of crop residue (Robertson & Simpson, 1988). Larval development continues from autumn to 232 CHARLET ET AL. spring. The mature larva makes a cell in the soil in which it pupates. The adult emerges about 7 to 21 d later (Allsopp, 1979). Damage Larvae feed on decaying vegetable matter and crop residues in the soil. They also feed on newly germinated seeds and the growing points of plants, which results in patchy stands. Damage is most common in early planted crops, especially where crop residues have become scarce. During summer, adults may damage young plants, by surface feeding or cutting off the plant at, or near, ground level (Allsopp, 1979). Damage by both larvae and adults necessitates replanting in many cases. Cotyledons and growing terminals also may be attacked. Larvae are more troublesome in southern districts of Queensland, whereas adults are the most damaging stage in central and northern regions (Allsopp, 1981; Murray & Wicks, 1984). Management Strategies Natural enemies provide very little control. In southern areas, cool, wet weather in autumn, winter, and spring may cause a high death rate in false wire• worm larvae. Plowing of the previous crop and weedy summer fallow favors the survival of oversummering false wireworms. Clean cultivation during summer dries out the topsoil and eliminates weeds that provide food for the adults. False wireworm beetles are more damaging to sunflower seedlings where stubble is buried by cultivation compared with crops direct drilled through surface-retained stubble. This is because the surface-feeding beetles remain feeding on the stub• ble at the soil surface in the latter (Robertson & Kettle, 1993). Larvae are con• trolled by use of insecticide application at planting or insecticide seed treatment (Radford & Allsopp, 1987). Control of adults is obtained by baiting with insecticide-treated cracked grain that is broadcast evenly over the soil surface at, or immediately after, plant• ing (Murray & Wicks, 1984). This is practiced widely by sunflower growers throughout the Central Highlands of Queensland (Murray & Spackman, 1983). Where broadcast application is not possible the bait may be laid in trails spaced no more than 2 m apart (Murray, 1989). Growers in South Australia also control the false wireworm beetle, Celibe sp., with baits (Mowatt, 1979). Economic injury levels for adults have been determined and decisions on the requirement for treatment are based on the numbers of insects killed at bait mounds (Murray & Wicks, 1990). Accurate assessment of larval density by examining soil sam• ples is prohibitive because of the number of samples required and the time involved (Robertson & Simpson, 1988). The use of germinating seed baits is an effective method of detecting both adults and larvae (Robertson & Simpson, 1989).

Wingless Cockroaches, Caioiampra spp. [Orthoptera: Blaberidae]

Two species of wingless cockroachs, Calolampra elegans Roth and Princis and C. salida Roth and Princis, have become major pests in the new sunflower areas of the Central Highlands of Queensland (Swaine & Ironside, 1983). SUNFLOWER INSECTS 233

Description The adults are large (25-35 mm long) and shiny-brown with yellow stripes and margins (Color Plate 36). The male of C. solida is fully winged whereas the other adults are wingless (Allsopp & Hitchcock, 1987). The eggs are retained by the female until they hatch (Murray, 1985). Nymphs are initially grayish-brown or tan, developing yellow markings in the second to third instar (R.L. Mackay, 1994, personal communication). There are five to seven instars.

Life History Egg incubation times are about 8, 12, and 20 wk (2,3, and 5 mo) at 30, 25, and 20°C respectively (R.L. Mackay, 1994, personal communication). Generally nymph production begins in spring and continues throughout the summer. Nymphal development occurs through the summer and is most probably com• pleted by the onset of winter; however, some overwinter as late-instar nymphs, becoming adults in the spring. One mating is probably sufficient for life and adults can live for at least 2 yr. Females of C. elegans and C. solida produce nymphs in batches of about 40 and 30, respectively.

Damage Nymphs and adults are found under stubble but congregate around volun• teer plants in bare fallows. If the soil surface dries, they tend to move down to the moist soil layer (Murray, 1985). The cockroaches feed at night (Murray & Wicks, 1990). On small seedlings, they feed on cotyledons and stems, often severing the stem. On larger seedlings, they feed on the leaves and growing points.

Management Strategies Wingless cockroach populations reach highest densities under no tillage with stubble retained (Robertson, 1993). A tachinid fly, Chlorotachinafroggattii (Townsend), has been recorded parasitizing the nymphs (Cantrell, 1985; Murray, 1985), but parasitism percentages seem to be low, mostly <5% (R.L. Mackay, 1994, personal communication). When a sufficient number of wingless cockroaches are present prior to planting, as determined by numbers killed at samples of bait mounds (Murray & Wicks, 1990), control is obtained by baiting with insecticide-treated cracked grain bait (Murray & Wicks, 1984).

Cutworms, Agrotis spp. [Lepidoptera: Noctuidae]

Several species of cutworms attack sunflower in Australia (Broadley & Ironside, 1980a). Four species of Agrotis have been found: brown cutworm, Agrotis munda Walker; bogong moth A. infusa (Boisduval); black cutworm, A. ipsilon (Hufnagel); and variable cutworm, A. prophyricollis Guenee. 234 CHARLET ET AL.

Description Cutworm moths are dull-colored and stout-bodied with a wingspan of about 40 mm. Eggs of all species are pearly-white. There are five larval stages and full-grown larvae measure up to 50 mm long. Overall color may be gray or brown, depending on the species, and the surface often has a roughened, granu• lar texture. Cutworm larvae characteristically curl up and lie motionless when disturbed (Allsopp, 1977). The brown pupa is smooth and shiny, about 20 mm long, and tapers sharply towards the posterior end.

Life History Eggs are generally laid on soil under low-growing plants and sometimes among organic material on the soil surface (Swaine & Ironside, 1983). The lar• vae, which emerge after a few days, usually feed at night and hide during the day in the soil. However, feeding may occur on dull, cloudy days (Allsopp, 1977). The larval stage usually lasts 4 to 6 wk. Mature larvae pupate in an earthen cell in the top 5 cm of soil, often under some object. The time for pupal development depends on temperature and moisture and may vary from 14 d to many weeks. The life cycle from egg to adult takes about 8 wk (2 mo) in the warmer months (Swaine & Ironside, 1983).

Damage Cutworm larvae generally sever the stems of young seedlings at, or near, ground level, thereby causing collapse of the plant. Sometimes the young plant is partially dragged into the soil, where it is fed upon by the cutworm larva. Crop areas attacked by cutworms tend to be patchy, and destruction of available seedlings in a given area may force the cutworms to migrate to adjacent areas (Swaine & Ironside, 1983).

Management Strategies Cutworms are attacked by a wide range of parasitoids, predators, and dis• eases. The cultural practice of clean fallow helps to reduce the opportunity for cutworm infestation (Swaine & Ironside, 1983). Insecticides are used to give control when damage warrants. A late-after• noon spray, close to the time when the larvae will commence feeding, gives best results (Forrester, 1980a).

Black Field Earwig, Nala lividipes (Dufour) [Dermaptera: Labiduridae] Although a pest mainly of maize (Hargreaves, 1970), the black field earwig also is a sporadic pest of sunflower (Broadley & Ironside, 1980a).

Description Adults of N lividipes occur as three forms, females and major and minor males (Simpson & Mayer, 1990). In seedling crops, major males are about twice SUNFLOWER INSECTS 235 as abundant as minor males, but females are only slightly less common than males (Simpson et aI., 1992). Simpson (l993a) described the eggs as ovoid, creamy-white, glossy, and without obvious sculpturing. The abdominal segments of the embryo become visible through the chorion as development proceeds. They are about l.0 mm in length and 0.7 mm in width. Eggs are laid in clusters of approximately 25 to 30 (Hargreaves, 1970) just below the soil surface (Simpson, 1991). Nala lividipes appears to have five nymphal stadia, each of which can be distinguished by using the number of antennal segments and the extent of wingbud development (Simpson, 1993a). First-instar nymphs are pro• tected by their mother for the first 1 to 2 wk, but after that they must fend for themselves (Galloway, 1975). Life History The black field earwig lives in the soil and moves around in the upper few centimeters loosened by cultivation. The life cycle from egg to adult takes all summer in southern Queensland (Hargreaves, 1970), however in central Queensland multiple generations are possible during the summer (Simpson, 1993b). Numbers decrease during winter and surviving females lay their eggs in spring in batches of about 30 in the soil. Sunflower is of intermediate status as a host of black field earwig as life-table data indicate that earwig numbers remain constant when fed on germinating sunflower seeds (Simpson & Robertson, 1993).

Damage Nala lividipes damages sunflower in two ways (Simpson, 1989), by feed• ing on germinating seeds and seedling stems below the surface, or by chewing on the stems of newly emerged seedlings above ground. Management Strategies Black field earwig populations peak in density with intensive cultivation both with and without retained stubble (Robertson, 1993). The common brown earwig, Labidura truncata (Kirby), is a valuable predator of black field earwig (Franzmann et aI., 1992b) Earwigs are controlled by use of insecticides applied at planting and by baiting with insecticide-treated cracked grain, broadcast evenly over the soil sur• face at, or immediately after, planting at 5.0 kg/ha. This is twice the rate needed to control false wireworm beetles, wingless cockroaches, and field crickets. The thresholds for treatment of N. lividipes have been calculated (Simpson, 1993c) from the numbers attracted to germinating-seed baits (Robertson & Simpson, 1989).

Field Crickets, Teleogryllus and Lepidogryllus spp. [Orthoptera: Gryllidae] Two black field crickets, Teleogrylius commodus (Walker) and T. oceanicus (Le Guillou), and two brown field crickets Lepidogryllus parvulus (Walker) and L. comparatus (Walker) occasionally attack sunflower. 236 CHARLET ET AL.

Description The adults are about 25 to 35 mm long and are black or dark-brown. The hind legs are stronger than the other legs and are adapted for jumping. Males pro• duce a chirping sound by moving their wings. The female has a long ovipositor with which she places eggs in cracks in the soil. The eggs are banana-shaped, cream in color, and 2.5 to 3 mm long. They are laid singly from 1 to 4 cm deep in the soil (Goodyer, 1983a). The immature stages resemble adults in shape but are wingless and paler in color.

Life History Adults, which live for 8 to 12 wk (2-3 mos), are active in the warm months of the year. Egg laying is stimulated by rainfall. Each female may lay from sev• eral hundred to more than 1000 eggs during her life. Under favorable conditions, eggs laid in spring, summer, and early autumn hatch in 1 to 3 wk. The duration of the nymphal period for the spring and summer generations is 8 to 12 wk (2-3 mos) (Goodyer, 1983a). The egg is the overwintering stage in southern districts and the egg and late nymphal stages for the autumn generation in northern areas (Goodyer, 1983a). The crickets are sporadic pests and only occur in outbreak proportions when seasonal conditions favor their build-up. Outbreaks may occur when mild winters and springs are followed by warm, dry summers.

Damage Field crickets seek shelter during the day in cracks in the soil or under trash; coming out at night to feed on weeds, grasses, or crops. In sunflower, they feed on the leaves and stems of the seedling, sometimes severing the stem at or above• ground level. They also may attack more mature plants, feeding on the back of the flower head and on the maturing seeds on the face of the head (Forrester, 1980a).

Management Strategies Cricket populations are naturally regulated by weather conditions. Other natural control agents, including diseases, parasitic insects, and predatory birds and insects, appear to have little effect (Goodyer, 1983a). However, nematodes are common parasites of Lepidogryllus spp. in central Queensland (Simpson, 1994, personal communication). Field crickets are controlled by baiting with insecticide-treated cracked grain, broadcast at 2.5 kglha. The economic threshold for treatment of field crick• ets has been experimentally calculated (Simpson, 1993c).

Sugarcane Wireworm, Agrypnus variabilis (Candeze) [Coleoptera: Elateridae]

The sugarcane wireworm has a wide host range and occasionally attacks sunflower. SUNFLOWER INSECTS 237

Description The adult is a dark gray-brown click beetle about 10 mm long. Eggs are nearly cylindrical, about 0.6 mm long, and change color during development from white to yellow (Goodyer, 1983b). Wireworms have elongated, cream to yellow-brown, shiny, leathery, and flattened bodies with a wedge-shaped head and a forked, tooth-edged posterior. Larvae travel slowly through soil, and when handled, their movements are jerky and erratic. Newly hatched larvae are white and about 2 mm long. They develop through eight instars and when fully devel• oped are 15 to 20 mm in length. The pupae are white and 9 to 14 mm long.

Life History The beetles emerge during spring and summer and may live for 4 to 8 wk (1 to 2 mo). About 3 to 4 wk after emergence, the females start laying eggs, either singly on the soil surface or in clusters in cracks or crevices up to 50 mm deep. The eggs hatch in about a week. There is only one generation per year. The lar• val period lasts for about 9 or 10 mo and larvae may be found in the soil through• out the year. Larvae pupate during spring and early summer. Fully fed larvae con• struct earthen cells in the soil and adult beetles emerge after about 2 wk (Goodyer, 1983b ).

Damage Larvae feed on vegetable matter in the soil and also on the underground stems and roots of plants. Sunflower seedlings are damaged in the early stages of growth, up to the four- or five-leaf stage (Swaine & Ironside, 1983).

Management Strategies Wireworms appear to prefer undisturbed situations and are often found where plant regrowth or weeds occur. They can be controlled by use of insecti• cides applied at planting, by in-furrow applications, or by seed treatments (Radford & Allsopp, 1987). The use of germinating-seed baits is an effective method of detecting both adults and larvae (Robertson & Simpson, 1989).

FOLIAGE FEEDING SPECIES

Soybean Looper, Thysanoplusia orichalcea (Fabricius) [Lepidoptera: Noctuidae]

The soybean looper is an occasional pest of sunflower (Broadley, 1978).

Description Adults have a wing span of 35 mm and a shiny, golden area on the forewings. Eggs are deposited singly on the undersides of the larger leaves. They are whitish, slightly flattened, and about 0.5 mm in diameter. The caterpillars are 238 CHARLET ET AL. green with light-colored stripes and grow to 40 mm long. They are characterized by their looping form of movement. They occur predominantly on the leaves and are rarely found on the sunflower head (Broadley, 1978). Fully developed larvae are about 30 mm long. Pupae are formed inside a cocoon of threads. These are normally located on sheltered parts of the plant or in debris at the base of the plant.

Life History Larvae emerging from eggs after an incubation period of 3 to 4 d, begin feeding immediately. The larval stage lasts about 4 to 6 wk. Adult moths emerge after a pupal period of about 2 wk (Broadley, 1978).

Damage Larvae feed on the leaves. Tissue damage is insignificant during early lar• val development, but increases dramatically once larvae reach about 15 mm in length. Large, irregular-shaped holes in the leaves usually coincide with the appearance of large larvae (Broadley, 1978). Severe defoliation is uncommon.

Management Strategies Soybean looper infestations are often controlled by parasitoids, predators, and diseases before they cause much damage. Control is usually unwarranted although, caterpillars causing severe damage late in crop development can be controlled with insecticides if necessary.

Thrips [Thysanoptera]

The onion thrips, Thrips tabaci Linderman, is often found on sunflower plants. Other thrips recorded include the tomato thrips, Frankliniella schultzei (Trybom), the broadwinged thrips, Desmothrips tenuicornis Bagnall, and the plague thrips, T. imaginis Bagnall.

Description Adult thrips are tiny brown or black insects about 1 to 1.5 mm long with two pairs of narrow wings fringed around the margin with fine hairs. Eggs are deposited into the plant tissue. Nymphs are wingless, somewhat sluggish, and creamy or yellow in color. There are two quiescent "pupal" stages.

Life History Thrips are most abundant during a hot, dry spring following a mild, dry winter. The nymphs feed on the plant until fully grown, then they crawl down the plant and enter the soil. There they change to the prepupal and then pupal stages. After a few days, the adults emerge. Development from egg to adult takes about 2 wk. SUNFLOWER INSECTS 239

Damage Both adults and nymphs feed on the leaves by rasping the surface tissues and sucking the exuded juices. Thrips damage is normally insignificant; howev• er, when very heavy populations of thrips occur on seedlings, they cause distor• tion and browning of the cotyledons and leaves (Forrester, 1981). Under these conditions, seedlings can be severely stunted or killed.

Management Strategies No specific parasites of thrips are known. It is probable that predators reduce the population, but it is unlikely that their influence is comparable in extent to that of the weather. When necessary, control can be achieved by spray• ing with insecticide.

Greenhouse Whitefly, Trialeurodes vaporariorum (Westwood) [Hemiptera: Aleyrodidae]

The greenhouse whitefly is a sporadic pest in Australian sunflower.

Description Adults are about 1 to 1.5 mm long and appear to be white due to a cover• ing of white powdery wax. The adults congregate on the undersides of the leaves, but fly readily when disturbed. The tiny eggs, which are yellow at first and later tum black, are laid on the undersides of young leaves. The mobile first-stage nymph chooses a feeding site on the underside of a leaf. Later-stage nymphs are immobile, flattened, and oval in outline. The second- and third-stage nymphs are greenish-yellow and the fourth-stage nymph is white and about 0.75 mm long (Forrester,1980b).

Life History Eggs hatch in about 2 wk in summer, but the incubation period can be extended to more than 12 wk (3 mo) by cool or cold conditions. After hatching, nymphs crawl about on the underside of the leaf for up to 3 d before they settle down and commence to feed. Under favorable conditions in summer, the total nymphal period is about 3 wk, but in cooler weather it may last for more than 6 wk (Forrester, 1980b). After developing within the skin of the last nymphal stage the winged adult emerges. Males live for about 4 wk (1 mo) and females from 4 to 12 wk (1-3 mo) while laying several hundred eggs. Whiteflies can overwinter in the adult or egg stage. The whiteflies have a wide host range including vegetables, ornamental plants, and weeds. They do not develop on graminaceous plants.

Damage Nymphs and adults suck sap and excrete honeydew. A secondary infection develops when a black sooty mold fungus grows on the sticky honeydew. 240 CHARLET ET AL.

Sunflower usually displays no damage symptoms with low numbers of white• flies, but under very heavy infestations, plants lose vigor and damage is mani• fested under severe moisture stress, causing leaf wilting and failure to set seed (Forrester, 1980b).

Management Strategies An introduced parasitoid, Encarsia formosa Gahan, is widespread in Australia, and commonly attacks whitefly nymphs. In Australia there are no insecticides registered for control of whiteflies on sunflower.

CAPITULUM OR HEAD FEEDING SPECIES

Rutherglen Bug, Nysius vinitor Bergroth [Hemiptera: Lygaeidae]

Two species of Nysius are found on sunflower in Australia, N. vinitor and N. clevelandens is Evans. Although adults of N. clevelandensis are commonly found on buds and heads in Queensland (Broadley & Rossiter, 1982) and north• ern New South Wales, the species is very rare in Victoria and absent in south and western Australia. In addition, nymphs of N. clevelandensis are rarely found on sunflower (Franzmann et aI., 1992a) and thus it is of minor importance relative to N. vinitor.

Description Adults are small (about 6 mm long), dull-gray and possess two pairs of sil• very-gray wings (Color Plate 37). The elongate, slightly curved eggs are laid singly or in small clusters (2-5) in the corolla tubes of individual disk flowers. Smith (1927) described the eggs in detail. On the 1st d, they are creamy-white; on the 2nd and 3rd d, they develop bright red spots; and by day 6 or 7, they are dark fuchsia and iridescent. There are five wingless nymphal instars (Smith, 1927). Nymphs are pear-shaped and are often reddish in color.

Life History The egg incubation period requires 6 to 9 d (Newman, 1928; Malipatil, 1979). Nymphal instars 1 to 5 took 4 to 5, 3 to 4,6,6, and 4 to 8 d to develop, respectively (Malipatil, 1979). Newman (1928) recorded the total nymphal devel• opment period at 24 d. At 25 ± I DC and under two different photoperiods, Allsopp (1984) found nymphal development to be 23 to 25 d with no difference between the sexes. Under these conditions, mortality was 43.5%. Attia (1982) showed that all development parameters slowed during winter and he reared eight successive generations, under field conditions, during a complete year. The pre• oviposition period has been reported to range from 3 to 10 d (Newmann, 1928; Malipatil, 1979; Attia, 1982). Females, when maintained individually with a male at 25 ± 10 C, deposited a mean of 463 eggs. However, there was a large variation between females in number of eggs laid, and most eggs were laid between 1.5 and SUNFLOWER INSECTS 241

4 wk after adult eclosion (Newman, 1928; Malipatil, 1979; Allsopp, 1984). Attia (1982) recorded the mean number of hatched eggs per female at 140 to 269 at 26°C under a range of relative humidities. Adult males lived for 55 to 60 d (Malipatil, 1979). Starvation studies by Attia (1982) indicated that adults could probably sur• vive throughout the winter, occasionally feeding. There have been no reports of diapause and in Queensland breeding populations can be found in all seasons (Franzmann & Lloyd, 1994, personal communication). Adults invade sunflower crops at the bud stage. Numbers increase until 1 wk after flowering and start to decline 2 to 3 wk later (Franzmann et aI., 1994). Immigrant females contain immature ovaries, but become sexually mature during and soon after flowering. Oviposition begins within the 1st wk after flowering, increases for 2 wk and remains relatively constant for at least the next 4 wk (Franzmann et aI., 1994).

Damage Adults congregate on the stems of sunflower during budding and cause the head to either wilt, become grossly malformed, or die (Forrester, 1982) (Color Plate 38). Broadley et aI. (1986) showed that, in nonstressed sunflower crops, adults reduced grain yield and seed germination and increased free fatty-acid lev• els. Oil content of seed and fatty-acid composition of the oil were not substan• tially altered. Forrester and Saini (1982) reported that feeding reduced the linole• ic acid content ofthe sunflower oil. Damage in terms of grain yield, total oil con• tent, and germination was higher in moisture-stressed crops than in irrigated fields.

Management Strategies Nysius vinitor is difficult to control as it often appears suddenly in large numbers and only in occasional seasons. Its invasion of sunflower from weedy hosts is somewhat unpredictable since it is capable of migrating for 200 to 300 km in a single night by taking advantage of atmospheric disturbances for its trans• port (McDonald & Farrow, 1988). The tachinid, Alophora lepidofera (Malloch), is a common though low• level parasitoid of adult N. vinitor (Forrester, 1979; Malipatil, 1979). Forrester (1979) reported the discovery of an egg parasitoid, Telenomus sp., and later sug• gested that high levels of parasitism may be the reason why nymphal populations do not develop in late-sown crops (Forrester, 1982). Franzmann and Lloyd (1994, personal communication) found that Telenomus sp. near nysivorus Huggert is an important biological control agent, particularly in the fall. Insecticides are available for control; although, reinvasion by adults after treatment can occur rapidly (McDonald et aI., 1986). Franzmann et aI. (1992b) recommended an insecticide application during the pre flowering period if there are more than 10 adults/head in August to December or 20 adultslhead in January to April. A postflowering application is recommended if there were more than 25 adults/head up to the end of January and 50 adultslhead in January to April. 242 CHARLET ET AL.

If populations warrant insecticidal control, the insecticides should be applied at the critical growth periods of budding and/or after seed formation but before the heads turn down (Broadley & Rossiter, 1980).

Green Vegetable Bug, Nezara viridula (L.) [Hemiptera: Pentatomidae]

The green vegetable bug is a sporadic pest of sunflower, but it can be quite damaging when it occurs in large numbers (Forrester, 1980a).

Description The adult is shield-shaped and about 15 mm long. It is usually grass-green, but overwintering adults become brownish-purple during hibernation. Eggs are deposited in clumps of20 to 150 on the lower surface ofleaves. Nymphs are ini• tially orange-brown. As they grow, they develop black, yellow, and red patterns but green predominates in later instars (Swaine & Ironside, 1983). There are five molts in the nymphal stage.

Life History The eggs hatch in about 5 to 9 d. The newly emerged nymphs remain clus• tered near the egg shells for a day or two. The nymphal stage lasts about 4 wk. The life cycle takes about 5 wk in summer.

Damage Both adults and nymphs feed by sucking sap from the plant. The point of attachment of the stem to the head is a favored feeding site, and wilting of the head can result (Broadley & Ironside, 1980b). Feeding also causes malformation of the flowers and possibly reduced seed set.

Management Strategies The introduced egg parasitoid, Trissolcus basalis (Wollaston), is an effec• tive controlling agent in coastal areas of eastern Australia. Heavy infestations feeding on the stem at the back of the head should be controlled immediately with insecticides (Forrester, 1980a).

Budworms, Helicoverpa spp. [Lepidoptera: Noctuidae]

There are two important budworm pests of sunflower in Australia, the native budworm, Helicoverpa punctigera (Wallengren), and the com earworm, H armigera (Hubner). The proportion of each species on sunflower varies according to time of planting in any particular year and also from year to year. During 1979 to 1982 in south Queensland, H punctigera predominated during January and H armigera at other times (Broadley, 1984) SUNFLOWER INSECTS 243

Description Adults are drab and fawn-colored with a wing span of 35 to 40 mm. They are nocturnal and usually rest on the crop plants during the day. Eggs are nearly spherical and pearly-white when first deposited but later develop an encircling, irregular, brown band. The dark head capsule and gray body of the developing larva can be seen through the translucent egg shell prior to hatching. Larval col• ors are very variable and include light and dark-green, orange, brown, black, and pink. Larvae grow up to 40 mm long (Swaine & Ironside, 1983). When first formed, pupae are light-green and soft-bodied. However, pupal cases rapidly harden and tum dark-brown (Broadley, 1977).

Life History Budworms undergo pupal diapause during the winter, emerging in spring to attack a wide variety of hosts. On sunflower, eggs are deposited on the flower bracts and on the upper surface of the leaves at the tip of the plant from the bud stage through flowering (Broadley, 1978). Eggs hatch in 3 to 5 d in the summer. After hatching, larvae often favor the underside of the head bracts as feeding sites. Small larvae also may be found among the disk flowers while larger larvae feed on all parts of the head. Larvae feed for about 2 to 3 wk before leaving the plant and pupating in the soil, and moths emerge 2 to 3 wk later. The moths feed on nectar before mating and females begin to lay eggs when 3 to 6 d old. As many as 1500 eggs may be laid by a female over a 14-d period.

Damage Although damage is obvious and appears serious, it is considered that bud• worms are not of major economic importance in sunflower as the plant is able to tolerate large infestations and still produce a worthwhile yield (Swaine & Ironside, 1983). Caterpillars feed on the leaves, buds, petals, or on the small green bracts surrounding the head. They also burrow into the back of the head or feed on the tops ofthe developing seeds on the face of the head (Forrester, 1980a). Damage to the developing seeds is usually of little consequence unless infestations are particularly heavy. However, caterpillars feeding on the back of the head can pre• dispose the crop to secondary head rots. Stressed dry land crops are more prone to head rots than unstressed irrigated crops (Forrester, 1980a). When heavy infesta• tions occur in the bud stage, severe damage can result. The larval feeding can cause deformation of the seedhead and sometimes loss of the head by the larvae chewing into its connection with the stem (Broadley & Ironside, 1980b).

Management Strategies Both the native budworm and the com earworm have many natural enemies such as egg and larval parasitoids, predaceous coccinellids, neuopterans, hemipterans, coleopterans, earwigs, spiders; and various diseases (Zalucki et aI., 1986). Eleven species of larval parasitoids have been reared from Helicoverpa 244 CHARLET ET AL. spp. on sunflower in south Queensland and parasitization sometimes exceeds 30% (Broadley, 1984). At the bud stage, the caterpillars are concealed within the bud bracts and are very difficult to control with insecticides. When spraying is considered nec• essary, it is best to wait until the buds are just beginning to open and the yellow petals are becoming visible. Spraying earlier than this may give poor results, whereas spraying later can affect pollination by bees (Forrester, 1980a). The requirements for insecticide treatment for control of larvae in sun• flower remains some what problematical. Broadley (1978) advised spraying high populations at budding, and Forrester (1980a) considered that only very heavy infestations (more than 2 larvae/head) were worth spraying. Murray and Wicks (1986) found that an initial larval population averaging 17/plant during the post• flowering phase of crop development caused no significant reduction in yield in the absence of secondary head rots, and they agree with Broadley (1978) and Forrester (1982) that insecticide spraying is unlikely to reduce head rot.

INSECT PESTS OF STORED SUNFLOWER

Stored sunflower seeds are susceptible to most of the same insects and mites infesting other stored commodities. Infestations are likely if sunflower seeds are stored for long periods, if bins are not properly cleaned or maintained, and if the seeds are stored with a high-moisture content. There are three predom• inant insect pests of stored sunflower (McBride, 1981). These are the sawtoothed grain beetle (Oryzaephilus surinamenis L.) (Coleoptera: Cucujidae), the red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and the Indianrneal moth (Plodia interpunctella (HUbner)) (Lepidoptera: Pyralidae). Many other stored-product insects are potential pests.

Description and Life History Sawtoothed grain beetles are small (2.5 mm) flattened beetles with six lat• eral projections on each side of the thorax. Larvae have brown heads and white bodies 3.2 mm in length. They have a rapid life cycle and pass through four to six generations per year. They have a worldwide distribution. The red flour beetle is a reddish-brown beetle about 3.6 mm in length. The larvae are browish-white in color and have six legs. They are very active beetles and may live for up to 2 yr. The larval period is from 4 to 12 wk (1-4 mo). The red flour beetle has a worldwide distribution but is not common above the 41 st parallel in the USA. Indianrneal moths are very general stored pest insects and are the major storage pest of sunflower. The adult moth is 12.7 to 19.1 mm in length. The front and base of the wings are grayish-white and the wingtips are reddish-brown as is the body. The larvae are small, whitish-colored caterpillars, often with a pink or green tinge. The head is light-brown. The length of the larval period is extreme• ly variable ranging from 2 wk to 2 yr. Mature larvae move to the grain surface SUNFLOWER INSECTS 245 and pupate under a silken web. They have a cosmopolitan distribution (McBride, 1981 ).

Damage The sawtoothed grain beetle is an external feeder and damaged seed appears scarred and roughened. Damage usually appears following infestation by another species because they are unable to attack intact seeds. They feed on cracked seeds and seeds damaged by another storage pest. Red flour beetle larvae feed inside the seeds. If the seeds are disturbed, large numbers of adults and larvae will be seen crawling over the surface. They feed on high-moisture, intact seeds, broken seeds, and dust. Indianmeal moth larvae feed on the surface of stored grain. Infested seed will be webbed together and fouled with frass and cast skins. Larvae feed within the webbing (McBride, 1981; Metcalf & Metcalf, 1993).

Management Strategies The most effective management strategy is to prevent the initial infestation by proper sanitation. Before placing seeds into storage, bins should be thorough• ly cleaned of all stored grain to prevent any carryover from a previous infestation. In some locations, residual bin sprays are used to destroy hidden infestations in a bin before filling with new seed. However, residual bin sprays are not registered for sunflower in the USA. Seeds should be inspected as they are placed in stor• age. Seeds stored for long periods are likely to become infested. Thus, the seeds should be routinely inspected for insects and also for hot and moist spots. Warm, moist areas in stored seed indicate insect or mold activity. Aeration to bring the grain temperature down to SOC or less will prevent insect activity but will not kill them. In warm seasons, fumigation may be necessary but should not be done unless the grain temperature is at least IS.SoC. For an Indianmeal moth infesta• tion, applications of Bacillus thuringiensis can be used (McBride, 1981; Metcalf & Metcalf, 1993).

POLLINATION

Sunflower is naturally self-incompatible (Hurd et aI., 1980) and except for H agrestis (Pollad) and a particular strain of H annuus, Helianthus species are obligate outcrossers (Heiser, 1969). The hermaphroditic disk flowers are designed to ensure outcrossing. Anthesis occurs early in the morning with the elongation of the style. This pushes the stigma and pollen out of the corolla tube. The receptive lobes of the stigma are closed at this time and unreceptive to pollen. On the following day, the lobes separate and the flower becomes receptive to pol• lination. If pollination fails to occur, the lobes continue to curl until they touch a pollen grain. This is a mechanism to allow self-pollination in the event outcross• ing does not take place. However, self-pollination is inefficient and the exception (Griffiths & Erickson, 1983). The lack of sufficient pollinators results in unfertil- 246 CHARLET ET AL. ized achenes that develop hulls without kernels. Empty hulls also develop due to genetics and environmental stress (Desmukh & Nachane, 1977; Knowles, 1978). In North America, honey bees and bumble bees (Hymenoptera: Apidae), and other wild bees (Andrenidae, Anthophoridae, Halictidae, and Megachilidae) are known pollinators of sunflower (Freund & Furgala, 1982; Parker & Frohlich, 1983; Sosa, 1988). There are hundreds of species of bees associated with sun• flower in North America (Hurd et aI., 1980). These include bees whose primary association is with Helianthus as well as polylectic bees. Some bees visit Helianthus solely for nectar and some parasitic bees also visit Helianthus (Hurd et aI., 1980). Insects other than bees are unimportant as pollinators of sunflower in the USA (Parker, 1981b). In South Africa, the spotted maize beetle, Astylus atromaculatus, a pollen feeder, was as efficient as honey bees in pollinating sunflower in cage trials (du Toit, 1990). However, the spotted maize beetle is seasonal in occurrence and is considered a pest, thus its usefulness as a pollinator is limited. The honey bee was the predominant pollinator in three South African locations sampled for sun• flower pollinators (du Toit & Holm, 1992). Most honey and bumble bees foraging on sunflower collect nectar; howev• er, at times pollen collection predominates (Tepedino & Parker, 1982; Fell, 1986). Native oligolectic bees are more efficient pollinators of sunflower than are honey or bumble bees, especially on male-sterile sunflower (Parker, 1981a). Sunflower cultivars vary in their attractiveness to bees. Head size is not related to bee attractiveness and Parker (1981 b) did not find a clear relationship between bee preference and nectar volume or percentage of dissolved sugars. The sunflower leafcutter bee, Eumegachile pugnata (Say), has been inves• tigated as a manageable, alternative pollinator to honey bees. It has several favor• able characteristics including gregarious nesting, overwintering populations that can be stored, the ability to synchronize summer emergence with sunflower bloom, and bees that can be trapped from wild populations and be transported from field to field in artificial nests (Parker & Frohlich, 1983). Managed pollination in sunflower is used to maintain the genetic purity of selected germplasm, to produce hybrid seed, and to increase yield in F 1 commer• cial fields. Wild Helianthus is an important source of genetic material for improvement of commercial sunflower and maintaining a source population requires a periodic increase of pure seed. The multibranched habit and small head size of wild Helianthus make hand pollination inefficient and the heads are high• ly self-incompatible. However, placing the plants in cages with honey bees is effective in producing genetically pure seed (Collison & Wilson, 1985). Insect pollinators, especially honey bees, are the primary pollinators used for hybrid seed production, which requires the movement of pollen from male to female lines. However, honey bee nonpreference for certain genotypes can result in low seed set. The amounts of glucose, fructose, and sucrose in sunflower nec• tar varies by genotype. Honey bee preference for sunflower genotypes is corre• lated with the proportion of sucrose in the nectar (Pham-Delegue et aI., 1990). It may be possible to improve outcrossing in hybrid production fields by selecting for increased sucrose content in nectar. Other factors preferred by honey bees include disk flowers less than 10 mm in length (Sammataro et aI., 1983) and large SUNFLOWER INSECTS 247 nectaries with more stomata (Sammataro et ai., 1985a). Ultraviolet absorbing and reflecting patterns on the ray petals and other parts of the sunflower head differ among genotypes and may affect honey bee preference. The tips of anthers are covered by simple and glandular trichomes that may dehisce or be collected by bees (Sammataro et ai., 1985b). The contents of the trichomes have anti-insect properties (Gershenzon et aI. , 1985; Rogers et aI., 1987), but their effect on bees is not known. Modem sunflower hybrids have been developed to be self-fertile (Fick & Rehder, 1977). However, even hybrid sunflower benefits from the cross pollina• tion that occurs when honey bees are present (Parker, 1981 b; Griffiths & Erickson, 1983 ). In some tests, honey bees have increased sunflower yield 10 to 15% or more by increasing seed set (Fick, 1979; Robinson, 1980; Freund & Furgala, 1982). Honey bee pollination also tends to result in a greater oil con• centration in the seeds (Krause & Wilson, 1981; Mahmood & Furgala, 1983). In some cases, the yield increase seen when pollinators are abundant is obscured by the phenomenon termed "artifact autogamy." Artifact autogamy is the compensation that occurs when partial autogamy is present and the plant responds by increasing the weight per fertile seed. However, the increase in seed weight is accompanied by a decrease in oil content (Robinson, 1980). Compensation for low seed set also occurs in response to mechanical destruction of disk flowers (Charlet & Miller, 1993). Low and Pistillo (1986) tested 25 geno• types for self-fertility and measured artifact autogamy as artifact ratio. An artifact ratio greater than one represented positive weight compensation when pollinators were absent. They found that if autogamy was 80%, then an artifact ratio of at least 1.28 was needed to compensate for low seed set when pollinators were absent or insufficient. They did not consider oil concentration. Because some insect pests attack sunflower when the plant is blooming (Charlet et ai., 1987) and pollinators are active, a conflict exists between the need for pest control and pollination. Insecticides commonly used to control pest insects also kill pollinators, although the careful timing of pesticide application can reduce losses. Thus, while insecticide use can protect yield by limiting pest damage, it may lower yield and oil concentration if pollination is insufficient. Krause (1983) found that the gain obtained by using an insecticide to control the sunflower moth was offset by the lowered yield resulting from reduced pollina• tion. The result was a lowered economic return when insecticides were used.

ACKNOWLEDGMENT

We appreciate the assistance of G. Bujaki (Hungary), Zoltan Horvath (Hungary), D. Camprag (Yugoslavia), and S. Masirevi (Yugoslavia) in providing information and literature for the section of this chapter on insects of central and eastern Europe.

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