J. Range Manage. 54: 462Ð465 July 2001 Anti-quality effects of feeding on rangeland plants: A review

JOHN B. CAMPBELL

Author is professor, Department of Entomology, University of Nebraska, West Central Research and Extension Center, Route 4ÐBox 46A, North Platte, Nebr. 69101-9495.

Abstract Resumen

The anti-quality effects of the major groups of insects that uti- Se discuten los efectos anti-calidad de los principales grupos de lize rangeland plants for food is discussed. The biology, ecology, insectos que utilizan las plantas del pastizal como alimento. geographical distribution and economic thresholds of grasshop- También se revisó la biología, ecología, distribución geográfica y pers, crickets, Western harvester ants, ranch caterpillars, big- umbrales económicos de chapulines, grillos, hormigas cosechado- eyed or black grass bugs, and white grubs are reviewed. Also dis- ras del oeste, orugas de rancho y pulgas ojonas o chibches negras cussed are practical pest management strategies if they exist. de zacate y gusanos blancos. También se discuten las estrategias Most of these rely on the integration of good range management practicas del manejo de plagas, si ellas existen. Muchas de ellas practices and the control strategy. se basan en la integración de buenas practicas de manejo del pastizal y la estrategia de control.

Key Words: Grasshoppers, harvester ants, range caterpillar, big eyed bugs, rangeland insects. or more species present at a certain type of range, only 8 or 9 species are really causing economic losses. Some species are con- In the United States, over 1,500 species of insects have been sidered beneficial in that they fed only on plants that are consid- noted as being in association with the range ecosystem (Kumer et ered detrimental to the range. For example, Hypochlora alba al. 1976, Thomas and Werner 1981). Fortunately, most of these (Dodge) feeds primarily on Louisiana sagewort, Artemsia ludovi- are not economic in terms of detrimental effects on range plants. ciana Nutt., and secondarily on Western ragweed, Ambrosia The best known damaging species belong to the order of psilostacka D.C. The genus Hesperottix feeds mainly on Western —grasshoppers, Hymenoptera—ants and termites, ragweed and Missouri goldenrod, Solidago missouriensis Nutt., Lepidoptera—caterpillars, Coleoptera—beetles, and Homoptera— (Campbell et al. 1974). leafhoppers. Insects are a significant factor in energy flow, nutri- Grasshoppers are classified as grass feeders, mixed feeders or ent cycling, water utilization and vegetative changes in a range forb feeders based on the mandibular type. Generally, the out- ecosystem. break populations belong to the mixed feeder group. Another Many entomology textbooks refer briefly to range insects, but classification is slant-face, to which most of the grassfeeders the 2 major publications that deal specifically and exclusively belong, and the spur throat to which most of the mixed feeders with the subject are Haws et al. (1982) “An Introduction to belong, and band-wings, which are mostly large grasshoppers Rangeland Insects of the Western United States” and Watts et al. that may be either mixed or forb feeders. (1989) “Rangeland Entomology”. This latter publication has been There are 3 life stages in the grasshopper life cycle—egg, noted as the world’s most authoritative treatment on the impor- nymph and adult. Eggs are deposited in soil and a frothy, sticky tant role of insects in rangeland ecosystems. Another publication material is secreted with egg deposition which forms an insulated of note is Pfadt (1994) “Field Guide to Common Western pod composed of soil particles. The number of pods and eggs per Grasshoppers”. This publication contains colored plates of adult pod varies with species. Some species deposit eggs in soil sur- and nymphs of the major rangeland grasshoppers, and the text rounded by roots of grasses; other species select open areas with details the biology habitat and feeding choices for each species. accumulations of surface debris. This publication by itself is a Wyoming Experiment Station Most grasshopper species overwinter in the egg stage, but a few Bulletin, but it is included in the USDA—APHIS Technical overwinter as nymphs. Hatching time is influenced by tempera- Bulletin 1809 “Grasshoppers Integrated Pest Management User ture and can be correlated with soil temperature. In the Northern Handbook”. This latter publication contains material by numer- Plains states, cool-season grasses such as needlegrasses (Stipa ous authors on range management considerations to reduce dam- spp.), wheatgrasses (Agropyron spp.) and bluegrasses (Poa spp.) age from grasshoppers and/or to reduce grasshopper numbers begin growth before grasshoppers become very active. By the based on range management techniques (Anonymous 1996). time grasshoppers begin to defoliate plants, these grasses have Grasshoppers are the most serious of the insect groups that con- completed growth and have enough energy reserves needed for tribute to the anti-quality of range plants. While there may be 50 spring growth the following year. The warm-season grasses such as the bluestems (Agropogan spp.), grama grasses (Bouteloua spp.) and buffalograss Buchloe doctyloides (Nutt.) Engelm., do Manuscript accepted 13 Sept. 00. not begin growth until May and grow most rapidly when temper-

462 JOURNAL OF RANGE MANAGEMENT 54(4), July 2001 atures reach 85Ð95¡F, which coincides with foot high and 30 feet in diameter. The area tion around the mouth and nose of live- the greatest grasshopper feeding activity. around the mound is denuded of all vege- stock. The larvae may tie several grass Grass responses to defoliation includes tation. Not only is the vegetation stems together with the cast skin. stoppage of root growth and nutrient destroyed, but wind erosion increases in Livestock tend to avoid grazing in these uptake for several days if more than half the denuded areas. The ants also collect areas because of the spines. of the green herbage is removed. “Shut- seeds that may affect plant production, As the populations become larger, food down” or “slow-down” periods in roots particularly with annual plants. Colonies consumption is heavy. They may destroy increase as severity and frequency of defo- survive for 15Ð20 years, and one mound all of the green grass down to and including liation increase. Removing more than 65% may consist of as many as 60 chambers. some of the crown. If drought conditions of the green herbage one time during the Winged reproductive ants may appear in exist, there is little regrowth, and the roots growing season can reduce total root May after a rain, but some also appear in are unable to store nutrients for the winter, length by 30% or more. If this occurs over the summer and fall. New colonies are and there is no reseeding of annual plants. several years, plants become weak and die formed by mated queens usually in later As they search for food, caterpillars gath- (Campbell et al. 1998). summer. After mating, the queen sheds er in bands a meter or more wide and sever- Damage caused by grasshoppers is more her wings and digs a burrow several inch- al kilometers in length. Ranchers refer to than actual consumption of forage. They cut es deep in the soil. The first brood is com- the feeding of these bands as “windrow- stems and blades while eating only part of posed mostly of female workers. This ing”. The range caterpillar feeds on 40 or them. They eat closer to the ground than brood forages, enlarges the colony, cares more species of grass (Wildermuth and livestock and may kill growing tips of for the young and protects the mound. The Caffrey 1916, Capinera 1978). Huddleston grasses. They cut off seed stocks, reducing workers move the eggs of the second et al. (1976) established the economic seed production, and soil erosion may result brood to newly-constructed chambers threshold as 2 large larvae/m2. Similar val- from denudation by heavy populations. which have been stocked with seeds and ues were derived by laboratory and model Personnel from the Bureau of insect parts as a food source. studies (Bellows et al. 1983, Capinera et al. Entomology and Plant Quarantine kept Most of the mound expansion is in the 1983, Riley et al. 1984). seasonal grasshopper density records for spring, but there is no regrowth in the The adult range caterpillar is a buff to western ranges from 1932—1952. They denuded area later in the season. Lavigne brown moth with a wing span of 50Ð70 estimated that the average number of 1.2 and Fisser (1966) estimated that a single mm. The female mates and deposits eggs grasshoppers/m2 would eat or destroy acre of rangeland supported as many as 15 and dies within about 3 days. Eggs are 14.65 million tons of forage on the 262 colonies. Worker ants from this number of deposited in cylinder-shaped clusters on million acres of western rangeland. This colonies stripped vegetation from as much plants. Larvae undergo six molts before would have provided feed for another 4.9 as one-seventh of an acre. As is true for pupating. This takes 12Ð14 weeks if hatch million units (unpublished data grasshoppers, overgrazed range suffers the occurs in the spring but only 7 or 8 if the Cowan and Bell 1973). most damage from the red harvester ant. hatch occurs in the summer. Crickets are close relatives of grasshop- Grazing management will serve to slow the The range caterpillar has in the past pers and have had sporadic outbreaks for increase of new mounds. Insecticides can be been considered cyclic which is probably over a century. In outbreak years, they used to treat the mounds, but this is labor true in the sense of large populations in increase in number and form great migra- intensive and should be approached from an extensive areas. In recent years, some tory bands (Watts et al. 1982). During area-wide control effort to be successful. extensive damage has occurred in local- these outbreaks, they may denude the ized areas virtually every year. rangeland of practically all plants. They Rangeland CaterpillarÐHemilenca Control has changed from massive aerial have been reported to feed on 250 species oliviae Cockerill spray programs over large areas to smaller of range plants (Cowan and Shipman The range caterpillar has 3 discontinu- mist applications of pyrethroids to local- 1947). They seem to have a preference for ous populations, one in Mexico, one in ized areas. If the infestation is early and flower and seed parts reducing the reseed- southcentral New Mexico and the third in appropriate timing of insecticide applica- ing potential of the plants, and if denuding northeastern New Mexico, Colorado, tions occurs in a year with at least some occurs later in the year, the plant wouldn’t Oklahoma and Texas. Dubach et al. moisture, grassy vegetation may recover. be able to store nutrients in the roots for (1988) and Shaw et al. (1987) believe overwintering. The Morman cricket has a these were once a continuous population. White Grubs similar life cycle to grasshoppers except Currently the distribution of the 3 popula- Beetles from the family Scarabaeidae that they are wingless. All crickets in the tions are separated by brush-infested areas are among the most numerous on range. migratory band move in the same direc- which may have been devoid of brush in Those beetles that have grubs as the tion, and the movement is about 0.8 km earlier times. The caterpillar distribution is immature stage are the most damaging. In per day or 40 km (25 miles) in a season generally in blue grama-dominated range- most species, plant damage occurs from (Ueckert 1970). land at elevations between 1,350 and the grubs feeding on roots which kills the 2,400 meters. The northern distribution grass; however, adults of a few species Western Harvester Ants into Colorado is probably limited by also cause plant damage. Kumer et al. The genus Pogonomyrinex is the prima- decreasing late summer precipitation. (1976) collected 37 species from short- ry group of harvester ants in North Caterpillars consume grass, often down grass prairie in northeastern Colorado. America. Cole (1968) has described 22 to the crown, waste unconsumed portions Only 9 species of the group were associat- species. This group ranks next to of leaves as do grasshoppers, and in addi- ed with root feeding, most of the rest were grasshoppers in terms of rangeland dam- tion, discourage grazing because of urtri- dung beetles. The Phyllophaga spp. com- age. Lavigne and Fisser (1966) indicate cation spines from both the larvae and plex are the best known plant damaging the mounds created by the ants may be a their shed skins. These spines cause irrita- group (Anonymous 1971a, 1971b).

JOURNAL OF RANGE MANAGEMENT 54(4), July 2001 463 The white grubs (MayÐJune beetles) are Labops have vestigial hind wings, but grasshopper egg pods. This larval stage is creamy white with a shiny brown head, Irbisia have well-developed wings. termed triungulin. Within a month, the lar- have 6 prominent legs and are generally Adult females of the big-eyed bugs vae pass through three more stages with shaped like a “C”. Much of the damage on deposit eggs into grass stems in the fall. each becoming more sedentary. Finally, rangeland probably goes unnoticed if it is The nymphs hatch in the spring in the they change to the pseudopupae which is of moderate intensity. It is generally diag- warmer lower areas and later in the cooler the overwintering stage. As temperature nosed as plant stress as a result of drought. upland areas. and moisture increase in the spring, they Heavy damage may occur only in spots The black grass bugs were first noted as enter the final immature pupal stage from ranging from 10—100 meters in diameter. pests around 1950 when range improve- which adults emerge. There is 1 genera- In some areas such as the Nebraska ment programs were replacing native grass- tion per year. Sandhills, damage may occur only in wet es with introduced grasses especially The interest in the blister beetles is not meadows that are a valuable hay or graz- wheatgrasses. The large areas of a single from the standpoint of damage to range ing source. In addition to destruction of species of grass provided an excellent niche plants but because of the injury to horses the grass, other problems may occur. for the black grass bugs (Higgins et al. or other livestock. They may actually Annual weeds often invade and dominate 1977). A density of 156/m2 reduced seed ingest a blister beetle. The bodies of the the area for a number of years (Randolph head production in intermediate wheatgrass blister beetles contain a vesicant substance and Garner 1961). Drake (1964) suggests by 56% (Malechek et al. 1977). Ansley and called cantharidan. This substance causes that feeding by white grubs creates a mode McKell (1982) showed the black grass bug blisters on skin tissue upon contact. It is of entry for bacterial and fungal diseases feeding reduced leaf length, seedhead usually ingested with the consumption of that kill the weakened plant. height and carbohydrate reserves in root alfalfa hay. Horses are very susceptible to Skunks and other rodents may cause fur- crowns in crested wheatgrass. blister beetle poisoning. Portions or all of ther damage to plants by digging up grubs Control strategies include application of the horse digestive tract can be severely as a food source. This occurs in Nebraska insecticides, (Hagen 1975, Dickerson irritated bringing about secondary infec- in the wet meadow areas. Although there 1978) or heavy grazing in the spring, tions and bleeding (Bauernfeind and are certain cultural or chemical control (Kamm and Fuxa 1977, Hagen 1975). Breeden 1984). Cantharadin is absorbed measures that reduce grub numbers, they Insect resistant varieties have also been and excreted through the kidneys, thus would only be economical to employ evaluated. Hewitt (1980) reported that tall, irritation of the kidney, ureter, urinary where a crop such as wheat is concerned. slender, intermediate and pubescent bladder and urethra could be followed by There is no practical economic method for wheatgrasses were somewhat tolerant to secondary infections and bleeding. The control of white grubs on rangeland. feeding by the black grass bugs. substance also lowers calcium levels and The life cycle of the white grub may take There are many other insect species that causes damage to heart muscle tissue. 3Ð4 years dependent on the species and cli- may sporadically cause severe damage to Capinera et al. (1985) conducted can- mate. Most of the damage is done in the rangeland in some limited areas. Termites, tharadin analysis on several species of second year. The beetles deposit eggs in armyworms, army/cutworms, leafhoppers, blister beetles commonly found in late spring or early summer. Some feeding plant hoppers, spittle bugs, wireworms, bill- Colorado. There were differences in occurs the first season. Grubs move below bugs and numerous others feed on range amounts found between species and sexes. the frost line until spring, then move close plants, but generally are not numerous enough Males apparently produce cantharadin and to the surface to feed on roots. The same to warrant expensive control techniques. pass it to females at mating. The minimum procedure occurs each year in the cycle. One other group of insects I was lethal dose of catharadin is about 1 When the larval cycle has been completed, requested to mention are blister beetles. mg/Kg. Thus a few beetles with a high an earthen cell is prepared and pupation Blister beetles are generally considered catharadin level would kill a small horse, occurs within the cell. The adults remain in beneficial in that the larvae of several but quite a few with a low level would be the cell until spring when they emerge and species are predacious on grasshopper required to kill a large horse. start another generation. eggs. Others are predaceous in the cells of Extension entomologists field quite a few ground-dwelling species of bees. questions yearly from either horse owners Miridae (Plant bugs) Adult blister beetles tend to be gregari- or alfalfa producers on how to avoid buying Many species of this family are associat- ous, and several may be noted feeding on or selling alfalfa hay that contains blister ed with range plants. They have piercing the same flowering alfalfa plant. They also beetles. Generally, blister beetles are pre- sucking mouth parts with which they suck feed on soybeans and blooming goldenrod sent at the second and third cuttings, but juices from plants. and probably other plant species found in probably will not be in the first or fourth The black grass bugs are the best known a range plant complex. cuttings; however, in 1998 in Nebraska, of this group of insects. They are also called Adult blister beetles vary in size and blister beetles were still present at the time big-eye bugs because their eyes appear to be color, but are easily recognized by the of the fourth cutting. Inspection of bales is bulging from the side of their heads. There elongated, narrow, cylindrical and soft not practical because the gregarious behav- are 34 species from 2 genera; Labops and bodies. When viewed from above, they ior of the beetles might cause one bale to Irbisia in this group (Kelton 1980). have a constriction at the back of the head have a large number of beetles, and the Insects such as black grass bugs that where it attaches to the narrowed anterior next bale might not have any. For the same feed by sucking fluids from the cell have end of the thorax (Bauernfeind and reason, chemical control is probably not considerable impact on range plant quali- Breeden 1984). The life cycle of blister practical either unless hay for horses was ty, quantity and plant survival (Haws et al. beetles is complex with several different bringing a premium price. Dead beetles are 1982). The adults of this group are about 6 immature forms. Clusters of eggs are still toxic. Killing the beetles doesn’t mm long and are blackish grey, with buff deposited in the ground. Newly-hatched reduce the toxicity. margins around the edges of the wing. larvae move through the soil feeding on

464 JOURNAL OF RANGE MANAGEMENT 54(4), July 2001 Literature Cited Haws, B.A., J.F. Werner, D.B. Thomas, J.L. Watts, J.G., E.W. Huddleston, and J.C. Capinera, R.W. Lauderdale, J.B. Knight, Owens. 1982. Rangeland entomology. Ann. E.W. Huddleston, W. Smith, W.C. Rev. Entomol. 27:283Ð311. Anonymous. 1971a. White grubs Ð Nebraska. Campbell, J.D. Evans, A.F. Glover, B.E. Watts, J. Gordon, G.B. Hewitt, E.W. USDA Coop. Econ. Insect Rept. 21:373 Norton, and E. Arlo Richardson. 1982. Huddleston, H. Grant Kinzer, R.J. Anonymous. 1971b. White grubs—Colorado. Rangeland Insects of the Western United Lavigne and D.N. Ueckert. 1989. USDA Coop. Econ. Insect Rept. 21:488. States. Utah Agr. Exp. Sta. Spec. Rept. 23. Rangeland Entomology. Range Sci. Series Anonymous. 1996. Grasshopper IPM User 64 pp. No. 2. 2nd ed. 388 pp. Handbook. Tech. Bull. No. 1809. Hewitt, G.B. 1980. Tolerance of ten species of Wildermuth, V.L. and D.T. Caffrey. 1916. USDAÐAPHIS. Agropyron to feeding by Labops hesperins. 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