Life History and Ecology of the Sameodes albiguttalis,l a Candidate for Biological Control of Waterhyacinth2

c. J. DELOACH' AND H. A. CORDa' Biological Control of Weeds Laboratory, AgrL Res. Serv., USDA, Hurlingham, Buenos Aires Prov.,

ABSTRACT Larvae of the pyralid moth, Sameodes albiguttalis (Warren), caused heavy hut sporadic damage to waterhyacinth, Eichhornia crassipes (Mart.) Solms in Argentina. Females laid an avg of 300 eggs each, usually in injuries, on the plant leaves. The larvae fed inside the petioles and bud of the plant and pupated in white cocoons in the bulbous-type petioles. Eggs required 4 days to hatch, the 5 larval instars took a total of 21 days to pupate, and pupae took 7 days to emerge. In the laboratory, 95.6% of the eggs survived, 54.3% of the larvae, and 96% of the pupae. With optimum conditions in the laboratory, the population was calculated to increase 1.16 times! day, or 150 times! generation of 34 days, and to double each 4.7 days. Five generations! year occurred in the field, and maximum populations measured were 130 larvae and pupae/l 00 plants. A braconid parasitoid heavily attacked larval populations and a pathogen, Nosema invadens or m., infected all stages in the field in Argentina. Same- odes albiguttalis would probably be an effective control agent if released in regions where it is not native. A synergistic effect between it and weevils of the Neo- chetina is predicted. The factors affecting its potential effectiveness are discussed.

Waterhyacinth, Eichhornia crassipes (Mart.) Solms, fish (Ctenopharyngodon ide/la Valenciennes) (Andres probably orginated in tropical South America, but and Bennett 1975), but both of these organisms are man has taken it into most tropical and subtropical rather indiscriminate feeders and numbers sufficient areas of the world as an ornamental. There it has to control waterhyacinth probably would also great- escaped cultivation to become the most damaging ly reduce other aquatic vegetation. aquatic weed in the world. The literature on the Explorations to find more effective biological con- organisms known to attack waterhyacinth and the trol agents for waterhyacinth in South America were progress of research on biological control has been made by Vogt (1960, 1961), Silveira-Guido,' Ben- reviewed by Bennett (1967, 1973, 1974, 1977), nett and Zwolfer (1968), Bennett (1970), and since Coulson (1971), Perkins (1972, 1973b), Zettler 1967 by B. D. Perkins" and the authors from this and Freeman (1972), Andres and Bennett (1975), laboratory. Center (1975), and Freeman et al. (1975). Research has been underway at Hurlingham, Waterhyacinth is attacked in the U.S. by larvae Argentina, since 1967 to test and introduce of the native moth, Arzama densa (Walker), that into the United States for biological control that normally feeds on the closely related pickerel-weed would be both effective and that would attack only (Pontederia cordata L.) that is native in the U.S. waterhyacinth (DeLoach 1975a, b 1976, DeLoach (Vogel and Oliver 1969a, b). In addition, the mite, and Cordo 1976a, b, Cordo and DeLoach 1975, Orthogalumna terebrantis Wallwork, apparently has 1976, Perkins and Maddox 1976, Silveira-Guido been accidently introduced from South America and and Perkins 1975). As a result, 2 species of wee- attacks the plant over much of its range in the U.S. vils, Neochetina bruchi Hustache and N. eichorniae (Bennett 1970, Gordon and Coulson 1974, Cordo Warner, now have been introduced and released in and DeLoach 1975, 1976). Waterhyacinth is also at- (Perkins 1973a). Both appear to be reduc- tacked by certain plant pathogens in Florida (Free- ing stands of waterhyacinth but their dispersal into man et al. 1975). However, these organisms pro- other areas is relatively slow Perkins," (pers. comm.). vide but little control of waterhyacinth under natural Although the weevils were the 1st species introduced, conditions. Waterhyacinth is also heavily fed on DeLoach (1975a) rated the moth Acigona infuse/la by the native manatee (Trichechus manatus L.) and Walker as potentially the most effective biological in laboratory tests by the introduced white amur control agent for waterhyacinth; however, it may have too wide a host range to permit introduction. 1 : Pyralidae; subfamily Pyraustinae. 2 This research was supported by funds from the Office of He rated the pyralid moth Sameodes (="Epigagis") the Chief Engineer, Water Resources Division, District of Civil Works, Washington, DC. Received for publication Sept. 27, 1977. • Silveira-Guido, A. 1965. Natural enemies of weed plants. 3 Research entomologist. Present address: USDA-ARS, Grass- Final report. Unpubl. report, Dept. Sanidad Vegetal, Univ. de land. Soil and Water Research Laboratory, P. O. Box 748, Tem- la Republica, Montevideo, Uruguay. 128 pp. ple, TX 76501. "B. David Perkins, present address, Aquatic Plant Manage- • Ingeniero Agr6nomo. ment Laboratory, Agric. Res. Serv., USDA, Fort Lauderdale, FL. 309 310 ENVIRONMENTAL ENTOMOLOGY Vol. 7, no. 2

albiguttalis (Warren) as the 2nd most potentially type-species phyllisalis Walker, and the rest effective control agent. to Mimorista Warren, type-species Samea botydalis Silveira-Guido" in Uruguay conducted the 1st bio- Guenee. logical observations of S. albiguttalis and found that Munroe (1955) showed that the name Epipagis the larvae tunnel in the petioles and pupate in a properly applies to the species previously placed in silken cocoon in the bulbous part of the petiole. North American lists in Stenophyes Lederer, a genus Rao' in India, by using a culture reared from pupae incorrectly synonymized by Hampson (1899) with imported from Trinidad, reported that the eggs the unrelated CrocidopllOra Lederer. Though the hatched in 5-11 days, larvae developed in 12-41 species of Epipagis as thus interpreted are related days in different months of the year, and pupae in a general way to Sameodes, they have never been required 6-12 days for development. Although his included in that genus even in its broad sense, and studies were severely limited by disease in the cul- they had not been placed in Epipagis prior to ture, disease-free females laid a maximum of 216 Munroe's paper, except for HUbner's inclusion of eggs and he reared 8 generations in the laboratory the type-species when he established Epipagis. M un- in 9 mo and II days. roe included 3 North American species in Epipagis: Cordo and DeLoach (1978) studied the host the southeastern E. huronalis (Guenee); E. for- specificity of S. albiguttalis extensively and reported sythae Munroe, described from Florida, but now that it was safe to introduce into the United States. known also from the West Indies; and E. disparilis The following research was done during that study, (Dyar), from the southwestern United States and at Hurlingham, Argentina, from 1973-77 to deter- . These 3 species are very closely related, mine the life history of S. albiguttalis, its ecology in and at least 2 more also closely related species occur the field, and to estimate its potential effectiveness in tropical America, completing our present knowl- in reducing stands of waterhyacinth if introduced edge of the genus. The life histories appear to be into the United States. unknown, but there is no indication that the species are associated with aquatic plants or aquatic habitats. and Distribution The genus is related to Diacme and Mimorista (see Sameodes albiguttalis was described by Warren above), whose life histories also seem to be un- (1889) as Epichronistis (?) albiguttalis from 3 Q known. All 3 genera are related to the holarctic collected in 1874 by J. H. W. Trail from the Rio genus Mecyna Doubleday, whose larvae feed on Purus in the Amazon basin. Hampson (1899) listed terrestrial plants." it in the genus Pyrausta Schrank. The species was The type-species of Sameodes, S. cancella/is (sec subsequently transferred in the collections of the above), is common in weedy places over most of British Museum (Natural History) and the U.S. the Old World tropics. Its habits do not suggest National Museum to Sameodes Snellen, which that it has an aquatic food plant. Several closely Hampson (1918) sank as a synonym of Epipagis related species of Sameodes occur in different parts HUbner. However, as Pastrana" (pers. comm.) points of Asia. Guenee, the type-species out, Hampson did not publish the species transfer. of Samea Guenee, is closely similar in structure and The combination Sameodes albiguttalis (Warren) ap- habits to Sameodes cancel/a Us, and occupies com- pears to have been published first by Biezanko et al. parable habitats in the tropics and subtropics of the (1957), who listed the species from Uruguay, and New World. The life history is poorly known but the combination Epipagis albiguttalis (Warren) by the U.S. National Museum has larvae from "an un- Bennett and Zwi:ilfer (1968). The latter name is known weed," presumably terrestrial. Samea ec- used in the unpublished reports of Silveira-Guido," clesia/is has a few close relatives in the Neotropics; Rao,7 and of this laboratory. these species may have similar life histories." How- Munroe" (pers. comm.) states that the taxonomy ever, another less closely related species at present is complicated by both nomenclatorial confusion placed in Samea, namely S. multiplicalis (Guenee), and incompletely resolved mistakes and uncertainties is known to feed on Salvinia, Pistia, and other in the generic classification. He believes that al- aquatic plants, including waterhyacinth under some biguttalis probably belongs to an unnamed genus and conditions (Bennett 1966, 1970, Bennett and Zwi:ilfer not to either Sameodes or Epipagis. As noted by 1968, DeLoach unpublished data). Samea multipli- Munroe (1950), the type-species of Sameodes is calis is abundant in Florida and widespread in the Old World tropical species Sameodes trithyralis tropical America. Samea nicaeusalis Walker and S. Snellen, a synonym of S. cancel/alis (Zeller). Though alophalis Hampson are neotropical species that close- in his 1950 paper he left a number of North Amer- ly resemble S. multiplicalis and which might be ican species in Sameodes, Munroe now feels that expected to have similar life histories. The genus some of these should be referred to Diacme Warren, Somatania Mi:ischler, with a single known species, S. pellucidalis Mi:ischler, recorded from Florida

7 Rao, V. P. 1972. Studies on four species of natural (Kimball 1965) and widely distributed in tropical enemies for biological control of Eichhomia crassipes. Unpubl. Rept., Indian Station, CIBC, Bangalore, India. 15 pp. America, is related and seems to be associated with 8lng. Agron. Jose A. Pastrana, Inst. Patologia Vegetal, aquatic habitats." Centro N acional de Investigaciones Agropecuarias, INT A, Villa Udaondo, Buenos Aires Prov., Argentina (pers. comm.). Reference in current or past literature of species "Eugene G. Munroe, Biosystematics Research Institute, Agri· culture Canada, Ottawa (pers. comm.). to such nominal genera as Samea, Sameodes, Epi- April 1978 DELoACH AND CORDO: ECOLOGY OF Sameodes albiguttalis 311 pagis, Diacme, and Mimorista should not in general pupae of S. albiguttalis were removed and placed be taken to indicate a probable aquatic host associa- with petioles in jars for transport to the laboratory tion. The life histories of most of the species that and subsequent rearing. really belong to these genera are unknown, but it Eggs and larvae used in the life history tests were seems likely that many if not most of them will reared from larvae and pupae dissected from the prove to be terrestrial. Also, many of the species petioles of waterhyacinth in the field. Each morning are grossly misclassified and will in time be trans- the adults that had emerged in 1/2 -liter paper cartons ferred to other genera or even subfamilies. For were transferred to 2-liter, screen-topped glass jars example, the species group that includes "Epipagis", containing leaves of waterhyacinth plants; sometimes "Chrysobotys" or "Sameodes" cambogialis (Guenee), adults were allowed to emerge from pupae in the Loxomorpha citrinalis Amsel (not to be confused jars with the plants. Ovipositional sites were made with "Sameodes" citrinalis Hampson), "Mimorista" available by breaking the pseudolamina between the fiavidissimalis (Grote) and "Mimorista" pulchellalis veins near the petiole, by cutting off slices or cutting (Dyar), as well as "Mimorista sp." of Costa Lima notches in the petiole, and by using leaves with and of Mann, has been recorded as feeding on cacti feeding lesions of weevils of the genus Neochetina and (somewhat questionably) on other terrestrial or of snails. All these methods exposed the spongy plants (Costa Lima 1968, Mann 1969, Pastrana" aerenchyma cells that preferred for oviposi- pers. comm.). However, this group belongs to a tion. Females mated and oviposited readily in the separate genus not very closely related to Samea, jars or in 1-m3 screen cages. Moths were provided Sameodes, Epipagis, or Mimorista." with a 1: 3 honey-water solution in sponges hung Pending completion of his current studies, Mun- from the tops of the cages as a standard rearing roeD recommends that albiguttalis be placed pro- procedure, but we did not determine if they actually visionally in Sameodes, as we have done in the fed. The jars were held in a temperature cabinet present paper. at 25°±2°C and a 16-h photophase from ten 40-w Sameodes albiguttalis appears to be distributed Gro-lux® fluorescent tubes. throughout tropical and subtropical South America. We did not attempt to transfer eggs to other Silveira-Guido' collected it from waterhyacinth in plants after they were laid, but the newly hatched Uruguay and at Iguazu (on the border between larvae were easily transferred with a small brush Argentina and ), Bennett and Zwolfer (1968) to punctures made in the petioles of other plants. collected it regularly from waterhyacinth in Trini- Plants for use in tests were collected from a stand dad, Guyana, Surinam, and the Amazon basin of of waterhyacinth in the Rio Reconquista near Hurl- Brazil, and during the present study we collected ingham that was not infested by S. albiguttalis or it near Buenos Aires, Argentina. Neochetina weevils. This stand was isolated by at least 15 km from any other known stand of water- Methods hyacinth. Plants used during larval development The population density of S. albiguttalis on water- tests or predation tests were held in hydroponic hyacinth was sampled during 3 yr in a small canal solution (described by DeLoach 1976) in 2-liter ca. 7 m wide near the Rio Parana at the town of containers or in small glass aquaria 36x28X35 cm Dique Lujan, 40 km NW of Buenos Aires, and at with a screen top. a site called "new canal" 2 km N of the small canal. Tests to measure fecundity, preference for oviposi- Also, samples were taken at 2 sites at Campana 70 tional site, duration and survival of eggs, larvae, km NW of Buenos Aires: at the inlet 1 km down- and pupae, and the rate of increase were all made stream from the Balneario Municipal, and at a in the 25°C temperature cabinet; other tests were lagoon of ca. 3 ha across the Rio Parana from the made at room temperature in the laboratory or in Balneario; these locations are at ca. 34° IS'S lati- the greenhouse. tude. When populations became highly diseased Our specimens of S. albiguttalis were first identi- in 1976, an isolated population that appeared to be fied by Pastrana" and later confirmed by Ferguson'· disease-free (i.e., normal fecundity, survival of adults and Munroe." Voucher specimens of the insects and eggs, and no microsporidian spores found in from these studies were deposited in museums of the adults) was found at Dique Los Sauces at La the USDA, Beltsville, MD, the Biosystematic Re- Rioja, 1000 km NW of Buenos Aires. According search Institute, Ottawa, and the Museo Argentino to the local water management authorities at Dique de Ciencias Naturales Bernardino Rivadavia, Buenos Los Sauces, waterhyacinth is not native there but Aires. was introduced into the lake since 1947. Two methods were used to sample population Results density. At the Campana lagoon, all the petioles Adult were examined ca. every 2 wk in either 4 or 8 Adult S. albiguttalis are yellowish tan with brown sampling units of l/.i m" at random locations within markings (Fig. 1). Females are darker, especially the stand of plants. At the Campana inlet and at on the forewings, than the males; the tip of the Dique Lujan, larger samples of several hundred female abdomen is tube-shaped and that of the male plants were examined at irregular intervals. In both ,. Douglas C. Ferguson, Systematic Entomology Laboratory, cases, the petioles were dissected, and larvae and Agric. Res. Serv., USDA, Beltsville. MD. 312 ENVIRONMENTAL ENTOMOLOGY Vol. 7, no. 2

Females usually laid their eggs in the exposed, spongy air-filled aerenchyma cells in injured areas of the waterhyacinth leaves where the epidermis had been removed by the feeding of weevils of the genus Neochetina, by snails, or by other causes; one egg fit snugly in each cell (Fig. 2A). Females also laid readily in areas where we had removed the epidermis with a knife or in cuts made in the leaf or petiole and in the cut ends of petioles. Less often they oviposited on undamaged plants. Eggs were usually laid singly in the laboratory, but groups of eggs in several adjacent cells were also seen. Of 983 eggs examined that were laid in the laboratory, 35.7% occurred singly, 16.5% in groups of 2,13.7% in groups of 3, 11.8% in groups of 4, 4.1 % in groups of 5, and lesser numbers in groups of 6-20 eggs each. In one test, we compared the preference of moths for ovipositing in feeding spots of Neochetina, in cuts made with a knife, or in undamaged water- hyacinth plants. In each replication, 1 ~ and 1 5

Table I.-Fecundity and survival of adult Sameodes albiguualis and viability of eggs.

Eggs laid Viability of eggs' Age of No. Eggs/ females females Survival % of ~ /day % (days) surviving (Ix) No. total (mx) I.mx No. hatch

1 19 0.499 1641 28.6 86.4 43.1 1421 84.4 2 19 .499 2399 41.8 126.3 63.0 849 98.2 3 19 .499 678 11.8 35.7 17.8 180 86.1 4 19 .499 659 11.5 34.7 17.3 349 94.0 5 13 .341 306 5.3 23.5 8.0 120 74.2 6 10 .263 27 0.5 2.7 0.7 16 50.0 7 6 .158 28 0.5 4.7 0.7 12 100.0 3 3 .079 0 0 0 0 0 9 1 .026 0 0 0 0 0 10 0 .000 0 0

Total 5738 150.6b 2947 Mean 302.0 89.1

• Includes only the 2947 eggs laid by It ~ from La Rioja; data were not taken on percent hatch of the other eggs. b Net rate of increase, Ro == times increase per generation. April 1978 DELoACH AND CORDO: ECOLOGY OF Sameodes albiguttalis 313

posed to 22 C(, 28 ~, and 8 moths of undetermined sex in a 0.7-m3 screen cage in the greenhouse in early December (sunset was at ca. 7:00 p.m.). The plants were changed and the eggs were counted periodically for 3 days. Females laid 84% of their eggs between 7 and 11 p.m. Results were as follows: Hour of day No. eggs laid 5-7 p.m. 15 7-9 p.m. 47 9-11 p.m. 81 II p.m.-8 a.m. 10 8 a.m.-5 p.m. 0 Egg The eggs of S. albiguttalis are creamy white, with- out obvious markings, ovoid, and 0.47 mm (0.40- 0.53) long by 0.37 mm (0.33-0.40) diam. Dura- tion of the egg stage was measured for 1109 eggs held at 24'±1.6'C. The eggs were laid by adults held at 24·C and dissected from the plants the morning after oviposition. The eggs were surface sterilized by placing a drop of 0.05 % sodium hypo- chlorite on them without subsequent rinsing; then they were held on wet filter paper in petri dishes and examined once a day for hatching. All eggs had hatched when examined on the 5th or some- times the 4th day after oviposition but we assume that they had hatched the night before, i.e., at a time halfway from the previous examination the afternoon before. Duration of the egg stage was thus 3-4 days. Viability was 89.1 % for 2947 eggs laid by 11 C( reared from pupae collected at La Rioja (Table 1). Of the total of 322 eggs that did not hatch, 202 were from 1 C( that apparently did not mate the 1st night; if these are excluded, 95.6% of the eggs hatched. Larva Newly hatched larvae fed just below the epidermis of the petioles and the feeding damage could be

Table 2.-0viposition by Sameodes albiguualis in wounded and undamaged waterhyacinth plants. FIG. 2.-Immature stages of Sameodes albigultalis: A) Eggs laid in exposed cells of a waterhyacinth leaf in the feeding lesion of a snail (ca. 40 eggs present), No. eggs laid on indicated B) Full-grown larva in its feeding tunnel in the petiole type of plant" (larva = 19 mm long), C) Cocoon in the bulbous petiole of waterhyacinth. With With Neochetilla Neochetilla feeding Rep. feeding lesions Undam- seen 1-2 days after hatching. Larvae from eggs laid no. lesions plus cuts aged on the pseudolamina tunneled within for 1-2 days and then apparently exited, crawled down the nar- 1 177 283 80 row part of the petiole, and entered again in the 2 289 505 26 3 116 299 28 globose part of the petiole where they continued 4 138 46 feeding (Fig. 2B). They appeared to feed singly, although several small larvae might feed in one Total 720 1554 134 petiole, and no gregarious habits were observed. In Mean eggs/ « 180 388.5 44.7 the field we usually found only one large larval plant. • Differences between all 3 treatments were significant at the 5% level according to Duncan's multiple range test. Full-grown larvae usually selected a pupation site 314 ENVIRONMENTAL ENTOMOLOGY Vol. 7, no. 2

Table 3.-Developmenlal lime and survival of each life stage of Sameodes albiguualis at 24°C in 3rd 56 .-----...Inslar the laboratory. 4th 48 lsI Instar " Inslar ~ Mean " width % survival ~ 40 ----. 2nd head Mean " Inslar capsule duration Each Cumu- e 32 ,-...... Stage (mm) (days) stage lative ,." " 5th ------~ 24 Inslar Egg 4 95.6 95.6 Larva 1st 0.23 3 8 2nd 0.40 4 3rd 0.57 3 o 4th 0.93 4 0.2 0.4 1.0 1.2 1.4 1.6 5th 1.33 7 Diameter of head capsule (mm) Total 21 54.3 51.9 FIG.. 3.-Frequency distribution showing number of Pupa 7 96.0 49.8 Sameodes albigultalis. larval mstars of Adult to peak oviposition 2 Total generation 34

in the mid-part of a globose petiole that had little prior feeding. The full-grown larva hollowed out Pupa a pocket, cut a round exit hole below it, tied the plug of plant epidermis from the exit hole in place Pupae of S. albiguttalis averaged 11.0 mm long with silk, and lined the exit tunnel with silk. The (range = 10.0-12.1) and 2.85 mm wide (range = larva spun a white cocoon and pupated (Fig. 2C). 2.5-3.1) for 5 & and 5

From the test on larval survival, one pupa died to year and between locations in the same year. In and 24 healthy adults emerged from the 25 pupae 6 yr of observations at several locations in Argen- recovered, a survival rate of 96.0% for the pupal tina, populations large enough to cause heavy dam- stage. Only one pupa was found in each of 23 age to waterhyacinth were found in only 4 instances: petioles and 2 were found in one petiole; the pupae in 1973-74 in the small canal at Dique Lujan; in were located in the bulbous petioles as previously 1975-76 at the Campana inlet, at the new canal, observed in the field. and at the small canal at Dique Lujan (Fig. 6). Generation Time and Rate of Increase In addition, populations reached 128 larvae and pupae/ 100 plants at the small canal at Dique Lujan In the laboratory at 25 ·C, a complete generation in Jan. 1977. The occurrence of generation peaks required 34 days: 4 days for the egg stage, 21 days in the field is based mostly on data from 1976. for the larval stage, 7 days for the pupal stage, and Counts made during the 1973-74 and 1974-75 2 days before the adult reached peak oviposition seasons generally confirmed these findings, but popu- (Table 3). lations were too low in those years for reliable The rate of increase at a density of 3 eggs/ plant measurements of generations. was calculated according to the method of Birch Sameodes albiguttalis appeared to have 5 gen- ( 1948) by using age-specific survival and fecundity erations in the field at Dique Lujan (Fig. 6). Gen- calculated from the previous life history data (Fig. eration peaks were in mid-Nov., Jan. 7 (49 days), 5) . The net rate of increase (times increase per Feb. 6 (30 days), and Mar. 18 (41 days). A 5th generation, Ro) was 150.6, the intrinsic rate of in- generation of larvae appeared ca. June 16 (90 days). crease (r ) was 0.14675, and the generation time n The 5th generation occurred in May 1975 but in (T) was 34.17 days. Thus, the finite rate of in- 1976 it was delayed until June by cool weather. crease (or number of times the population would Larvae of the 5th generation, and probably some increase per day = antiloger ) was 1.158, and 4.72 m from the 4th generation, overwintered in the petioles days would be required for the population to double of waterhyacinth. No pupae of the 4th generation (days to double loge 2/r ). = m were found in the field after June 16. Larvae of We should emphasize that this calculation of the the 5th (overwintering) generation began pupating rate of increase is valid only at an original density in Sept. (Fig. 6). of 3 eggs/plant on rather small plants. Density of the eggs, and subsequent degree of competition Damage Caused to Waterhyacinth between larvae and possible cannibalism by larvae, The larvae of S. albiguttalis damaged water- may be of great importance in larval mortality. Al- hyacinth by feeding inside the petioles and the bud though we never observed cannibalism, the 50% but they usually did not enter the plant crown. This larval mortality in these tests is difficult to explain feeding caused the petioles to break and die and unless some intraspecific competition or disease were killed the growing bud (Fig. 7). The large larvae involved. The eggs and larvae were taken from sometimes moved to other petioles or to other plants cultures believed to be pathogen free, but the micro- and might bore through several petioles just before sporidian is difficult to detect and its presence can- pupating. We found no evidence that the larvae not be ruled out; if present, the incidence of disease were vectors of primary plant pathogens but the might also increase with density. Thus, the rate of feeding did provide entry sites for invasion by facul- increase might be higher than calculated at lower tative or saprophytic microorganisms that caused larval densities and much lower at higher larval decay. The larvae damaged plants throughout the densities. growing season but reached a peak in mid-summer. Seasonal Abundance In heavy infestations, the plants did not recover before fall and suffered heavy die-back during the Populations in the field varied greatly from year winter. Damage done by S. albiguttalis to stands of water- hyacinth in nature was observed during 3 growing Egg 1.0 - Survlva' (1,1 seasons in the small canal at Dique Lujan and at Eggs/fema'e Campana. A small population of 12 larvae/IOO --. per day (m.) 0.8 plants was found in the 1st generation in Nov. 1973. The population increased in the 2nd generation, in g 0.6 .; Pupa Adull 150 Jan. 1974, to 28 larvae or pupae/lOO plants. Those ~ larvae severely damaged or destroyed the central ..•~ a'" '" 0.4 100 ~ part of the bud of most plants and 12% of all ,!;, 0+ , , •... on petioles s<;lmpledwere damaged. This damage, com- ,I ,, 0.2 50 ~ bined with heavy damage done by the weevils :.. w Neochetina bruchi and N. eichhorniae, greatly re- o o 10 15 20 25 30 35 40 45 duced the stand of waterhyacinth to the point that Age since eggs laid (days) by Aug. (mid-winter), the stand was estimated to FIG. 5.-Survival (at an initial density of 3 eggs/ cover only lis the area occupied the previous Jan. plant) and oviposition of Sameodes albiguttalis at 25·C. Stands are always reduced by cold weather during 316 ENVIRONMENTAL ENTOMOLOGY Vol. 7, no. 2

/973-74 40 Dique Lujan 20 Small canal o 0 ,\ 1974-75 , \ , \ 20 Campana Inlet I \ I \ I \ o 000 I \ 0 1974 -75 Dique Lujan 20 Small canal

0 80 /975-76 Campana Inlet 60

40

20

'" 0 -c: 1975-76 C Dique Lujan 0- 100 New canal 0 0 80 •... Q) 60 0- •... 40 Q) .Q E 20 :J Z 0 1975 -76 Dique Lujan 0 Pupae Small canal Larvae 140 2nd Gen 3rd Gen I ,~"'\ % Parasitized pupae 120 -c 4th Gen c -- % Dead pupae Q) 100 -c •... 0 80 E 1st Gen 60 '" A c'" 40 c.. a.. 20 ~

0 Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

FIG. 6.-Seasonal abundance of Sameodes albiguttalis determined from periodic field samples taken during 3 yr (% dead or parasitized may be read from the ordinate scale, i.e., 60 = 60 larvae/lOO plants or 60% para- sitized; % is based on number of prepupae or pupae inside cocoons on each date, not including other larvae in the sample). April 1978 DELoACH AND CORDO: ECOLOGY OF Sameodes albiguttalis 317

Competition with Acigona The larvae of both S. albiguttalis and Acigona intusella feed inside the petioles of waterhyacinth, and both are capable of causing heavy damage to the plant. The 2 species have similar life histories and behavior on waterhyacinth, but they seem to prefer different parts of the plant and therefore are ecologically separated. Several attempts were made to measure this separation, but sufficient populations of both species to make comparisons meaningful were present only in the inlet at Campana on Apr. 11 and 18, 1975. On both dateS, Acigona strongly preferred the tall slender plants (ca. 80 em high) and Sameodes preferred plants with globose leaves (ca. 25 em high) (Table 4). However, this dif- FIG. 7.-Typical damage to bud of a waterhyacinlh ference was not conclusive because of the small plant caused by larvae of Sameodes albigl/llalis. number of samples. Natural Enemies the winter but that in the small canal was reduced Sameodes albiguttalis is heavily attacked in the much more than in nearby areas exposed to similar field in Argentina by a parasitoid, a pathogen, and weather conditions. possible by predators. The solitary braconid, Hypo- Throughout the next growing season (Nov. 1974- microgaster n. sp." that emerged from the full-grown May 1975), the stand remained small, and the larva inside the host cocoon was the most abundant population of S. albiguttalis remained low; anchored parasitoid. The rate of parasitism increased in 1975- waterhyacinth, Eichhornia azurea (Swartz) Kunth, 76 from near zero in the 1st generation to 35 % in replaced waterhyacinth as the dominant plant. Maxi- the 2nd, to 50% in the 3rd, and to 90% in the mum populations on waterhyacinth that season were 4th in the small canal at Dique Lujan (Fig. 6). Less 6 larvae and pupae/ 100 plants in the 3rd genera- complete season-long data were obtained at other tion and 7/100 plants in the 4th generation (Fig. 6). locations, but the results were generally similar if By the spring of the 3rd season of observations moderate to large populations of host larvae were (Nov. 1975), the stand of waterhyacinth was again present. In 1975-76, parasitism at the new canal increasing but did not reach the abundance seen dur- at Dique Lujan reached 38% in the 2nd generation ing 1973-74: Nevertheless, populations of Sameodes and 100% in the 3rd generation; at the Campana larvae and pupae reached the highest levels seen- inlet it reached 83% in Mar. (Fig. 6). Populations 130/1 00 plants in the 2nd generation and 110/1 00 of S. albiguttalis were low during the spring of plants in the 3rd generation (Fig. 6). Populations 1976-77 at the small canal at Dique Lujan, and in the "new canal" at Dique Lujan (ca. 2 km NW parasitism was only 4% on Jan. 4, 1977; by Jan. 28, of the "small canal") also were very high, reaching populations had increased to 128 larvae + pupae/ 107/100 plants in the 2nd generation. 100 plants, and parasitism was 44.4%. Percent At Campana and the other areas sampled, popu- parasitism and disease was based on the number of lations of S. albiguttalis were generally much lower prepupae or pupae inside the cocoons on each date, than at Dique Lujan. In th 1973-74 season, a maxi- not including smaller larvae in the sample. mum of 4 larvae and pupae/lOO plants was found A 2nd braconid parasitoid was determined by in the lagoon at Campana, and in 1974-75 a maxi- Marsh,'" as Agathis sp. It also pupated inside the mum of 15/l 00 plants was found in the inlet at 11 Being described by Dr. Luis DeSantis, La Plata Univ., Campana. In 1975-76 a maximum of 42 in the La Plata, Argentina. ]2 Paul M. Marsh, Systematic Entomology Laboratory, Agric. 2nd generation and 15 in the 3rd generation/100 Res. Serv .• USDA, Beltsville, MD. plants were found in the inlet at Campana; only a few samples were taken in the lagoon during 1975- 76 and the maximum was 4/100 plants in the 2nd Table 4.-Preference of Sameodes albiguttalis and Acigona infusella for different phenotypes of water- generation. hyacinth in the field. The large population of S. albiguttalis in the 1973-74 season and the heavy damage it did ap- No. of larvae and pupae parently occurred because rates of parasitism (6.0%) collected/100 plants" and disease (7.7%) were low during the 2nd gen- eration in Jan. In the 1975-76 season, parasitism Type plant Sameodes Acigona in the 2nd generation was much higher (35 % ), and it increased through the 3rd generation. This prob- Short, globose 4.88 2.31 ably explains the population decline in the 4th and Tall, slender 0.00 28.51 5th generations. (Disease was also high but was ".A total of 389 globose plants and 221 slender plants ex- not measured.) ammed on 2 dates, Apr. 11 and 18. 1975. at the Campana inlet. 318 ENVIRONMENTAL ENTOMOLOGY Vol. 7, no. 2 host cocoon. Adults were ca. I cm long (twice as Sameodes albigllttalis ranks high in potential ef- long as Hypomicrogaster), and the female had an fectiveness, compared with other candidate insects, ovipositor ca. the length of the body. Agalhi.l' sp. for several reasons. The larvae attack the vital parts was rare, and only 2 adults were reared during the of the plant, the petioles and the bud, causing the studies. leaves to die and break off and preventing growth A microsporidian pathogen was found by Allen'" of the bud. Although the plant can still reproduce and identified by Maddox" as a Nosema species from offshoots, these new plants may be attacked by near Nosema invadens Kellen Lindegren, as deter- the next generation of larvae. The tunneling inside mined by host range studies and ultrastructural fea- the plant also allows the entry of secondary patho- tures of the spores. The pathogen appeared to infect genic organisms that cause decay. In Argentina, it all stages of S. albiguttalis; it greatly reduced fecun- appeared to cause heavy damage to waterhyacinth dity and longevity of adult moths, and infected fe- in the field, although the effect was confounded with males often died with the abdomen full of eggs. damage from the Neochetina weevils. However, the Fifteen females collected from a highly infected pop- damage was sporadic, apparently because of heavy ulation in the inlet at Campana in Feb. 1976 lived attack by parasitoids and pathogens. Apparently S. an avg of only 3 days (range = 1-5), laid an avg albiguttalis could increase to a population sufficient of only 29.1 eggs (range = 0-149), and only 26.5% to cause noticeable damage only in isolated stands of these eggs hatched. Healthy moths lived an avg where it could temporarily escape attack by these 5.7 days, laid an avg 302 eggs! 'j?, and 89.1 % of the natural enemies. eggs hatched (Table 2). On several occasions, The major factors limiting populations of S. (/1- 10-12 % of the pupae found in the field were dead, biguttalis in Argentina appear to be parasitoids and but mortality was probably much greater than this pathogens that probably are host specific. If these because dead larvae tend to disintegrate rapidly, and natural enemies can be eliminated in the "clean-up" most of them were not found. procedure before release in the field in the U.S., The 2 most common predaceous insects found S. albiguttalis should produce large populations in throughout the growing season in stands of water- the fall that would cause much greater damage to hyacinth were the coccinellid Coleomegilla quadri- waterhyacinth than seen in Argentina. Also, a larger fasciata Schon herr and the staphalinid Paederus sp.; overwintering population should result, producing a staphalinids were sometimes observed in the feeding larger Ist generation and more damage in the spring. tunnels inside the petioles. In petri dishes in the s. albiguttalis attacks waterhyacinth throughout its laboratory, 1 staphalinid adult ate alI 6 eggs of known climatic range in South America, so presum- S. albigullalis and killed 2 of 4 newly hatched larvae ably it would attack the plant throughout its range in 4 days; 2 adult Coleomegilla ate all 7 eggs they in the U.S., and in the rest of the world also. It were given in I day. These predators also were attacks waterhyacinth throughout the growing sea- placed on waterhyacinth plants in aquaria where son of the plant, although the spring buildup was moths of S. albigullalis were allowed to oviposit. somewhat slow and larval populations were reduced The predators appeared to reduce the number of in the fall, probably because of parasitism and dis- larvae of S. albiguttalis that were produced after 14 ease. days by half of that in a control aquarium without In order for S. albigllttalis to provide satisfactory predators. The tests were inconclusive because of control of waterhyacinth, it must overcome the insufficient replications and because the initial num- enormous capacity for increase of the plant and its ber of eggs laid was unknown, but they did indicate great capability to recover from damage. Sameudes that predators might reduce populations of S. albi- albiguttalis seems capable of doing this. Although gUllalis in nature. it does not produce a particularly large number of progeny per generation (which ranks low in Harris' Discussion and Conclusions (1973) scale), it produces several generations a The moth, Sameodes albiguttalis, appears capable year. The laboratory studies indicate that it has of giving good control of waterhyacinth if released the capacity to increase 150 times in each generation in the United States. The tests of Corda and De- of 34 days, or ca. 3 times that of the Neochetina Loach (1978) indicate that it is safe and will not weevils already released in Florida. Another ad- damage beneficial plants. Our findings confirm the vantage (not considered by Harris 1973) is that preliminary evaluation made by DeLoach (1975a) since it is a moth, and presumably a good flyer, it (based on the system developed by Harris 1973) should disperse and find isolated stands of water- that S. albigullalis has the greatest effectiveness hyacinth more rapidly than the Neochetina. weevils potential among the known candidates that have done to date. are safe to introduce. It should complement the Sameodes albigllttalis does not rank high in some effectiveness of the 2 weevils, Neochetina bruchi and factors in Harris' (1973) system. In addition to its N. eichhorniae, already released in Florida. How- low number of progeny, the full-grown larvae are ever, certain dangers to the insect exist that might rather small and they show no tendency to feed limit its effectiveness after release. gregariously; in fact, they may have some tendency

13 George E. Allen, Dept. of Entomology and Nematology, toward cannibalism. The effects of possible cannibal- Univ. of Florida, Gainesville, FL. ism and other density-dependent factors are not yet H Joe V. Maddox, Illinois Natural History Survey, Urbana. April 1978 DELoACH AND CORDO: ECOLOGY OF Sameodes albiguttalis 319 well understood, and they might greatly reduce the its natural host plant and S. albiguttalis presumably rate of increase, especially at higher population would be better adapted to it. The mite, Orthoga- densities. The effectiveness of S. albiguttalis as a lumna terebrantis, may also provide some competi- biocontrol agent has not, of course, been demon- tion for S. albiguttalis by making the leaves un- strated in another area of the world, since the pres- attractive as oviposition sites, especially in mid-sum- ent project will be the 1st introduction outside of mer when the mite is most abundant (Cordo and its native range (it was studied in quarantine in DeLoach 1976). 7 India (Ra0 ) but not released in the field). The greatest risk to effective control in the U.S. Sameodes albiguttalis is limited in host range to is that S. albiguttalis might be attacked heavily by E. crassipes and it may rarely complete its life cycle parasitoids or pathogens already present in the U.S. on E. azurea (Cordo and DeLoach 1978). This on other related insects in the same habitat (such habit ranks low in the system of Harris (1973), as the native moth, Arzama densa on pickerelweed who postulates that oligophagous insects are more and waterhyacinth). Muesebeck et al. (1951) listed effective control agents than monophagous ones. The 27 species of Microgaster (= Hypomicrogaster) and high degree of specificity does, however, make S. 55 species of Agathis from North America, the same albiguttalis safe to beneficial plants, without which 2 genera that contained species attacking S. albigut- it could not be introduced at all. talis in Argentina. Bennett and Zwolfer ( 1968) Sameodes albiguttalis appears to be generally com- reared 2 species of parasites from S. albiguttalis patible with the weevils Neochetina bruchi and N. collected in Surinam and at Belem, Brazil, Bracon eichJzorniae that have already been introduced. At sp., a gregarious ectoparasite of the larvae, and Dique Lujan in Argentina, a heavy attack by both Spilochalcis sp. from the pupae. Both of these Sameodes and NeocJzetina combined to nearly elimi- parasitic genera are abundantly represented in the nate waterhyacinth in one year. Sameodes albigut- U.S. Also, a microsporidian, Nosema sp., attacks talis could supplement· the control produced by A. densa in Florida (Habeck and Allen 1974) that Neochetina by attacking the growing bud, whereas might be able to infect S. albiguttalis when released. Neochetina attacks the crown. However, the species The attack of general predators in the U.S. will may compete to some extent since both tunnel in probably reduce populations somewhat, since they the petioles. also appear to attack eggs and larvae in Argentina, A synergistic effect between S. albiguttalis and but the effect probably would be much less than NeocJzetina is probable. Because S. albiguttalis pre- that of specific parasites. fers damaged leaf tissue for maximum oviposition Another possible danger to future control in the (although some eggs were laid on undamaged plants), U.S. is that the natural enemies of S. albiguttalis oviposition might be greatly increased if Neochetina present within its native range in South America were present to provide the feeding lesions. This might move naturalIy into the U.S. through Central effect probably was not critical in Argentina where America and Mexico. Waterhyacinth occurs at sev- the plants are much damaged by snails and other eral locations in Mexico but its distribution is not organisms, but in the U.S. where such damage is yet continuous to the U.S. Sameodes albiguttalis slight, the effect could be great. is not known to occur in Central America or Mexico Preliminary observations indicate that S. albigut- but its introduction there would provide a nearly talis and Acigona infusella are compatible because continuous bridge to the U.S. over which its natural they tend to attack different phenotypes of water- enemies might eventually migrate. If this occurs, hyacinth plants; also, S. albiguttalis attacks the bud the control of waterhyacinth probably would be re- and A. infuselia the plant crown. These results con- duced substantialIy. One of the greatest advantages firm the observations of Bennett and ZwoIfer (1968). of S. albiguttalis, that of an exotic organism free of This difference in ecological niche may explain, to- its natural enemies and free to increase possibly to gether with the difference in host range (Cordo and the limit of its food supply, would then be lost. DeLoach 1978), how the 2 species can coexist in Future research will attempt to measure the effec- the same area. Acigona infusella may compete with tiveness of S. albiguttalis in controlling waterhyacinth the Neochetina weevils since both feed in the plant after its release in the U.S. Of particular importance crown. The introduction of A. infusella might give is the assessment of the factors that reduce its added control of waterhyacinth but our observations effectiveness, especially of any parasitoids or patho- indicate that it would also damage the native gens of other insects already in the U.S. that may pickerelweed (Pontederia cordata) that is considered attack it. Surveys will also determine if it damages of value as food for waterfowl in the U.S. (Cordo any beneficial plants, especialIy pickerelweed. and DeLoach 1978). In countries where P. cordata If, after its release, S. albiguttalis proves ineffec- does not grow, or is not considered a valuable plant, tive in controlling waterhyacinth in the U.S., re- A. infusella would be a good candidate for intro- search could continue on the testing of other organ- duction. isms in Argentina known to attack the plant, such Sameodes albiguttalis wiII probably compete in as the moth Acigona infusella (Silveira-Guido 1971), the U.S. with the native Arzama densa since both the grasshopper Cornops aquaticum (Bruner) (Sil- attack similar parts of the plant; A. densa may loose veira-Guido and Perkins 1975), the scarab beetle out in this competition since waterhyacinth is not Chalepides luridus (Burmeister) (Silviera-Guido) ,. 320 ENVIRONMENTAL ENTOMOLOGY Vol. 7, no. 2 the fly Thripticus sp. (Bennett and Zwi:ilfer 1968), 1976. Biology of the waterhyacinth mite in Argen- and the rust pathogen Uredo eichhorniae Fragoso tina. Weed Sci. 24: 245-9. and Ciferri (Freeman et al. 1975).15 1978. Host specificity of Sameodes albigultalis in Argentina, a biologica] control agent for water- Acknowledgment hyacinth. Environ. Entomo!. 7: 322-28. Costa Lima, A. M. 1968. Quarto Catalogo dos in- The authors express their appreciation to Rosa sectos que vivem nas plantas do Brasil. Minist. da Ferrer, Josephine Runnacles, and Susan Walsh, tech- Agric. Lab. Centra] de Pat. Vegetal, Rio de Janerio, nicians of this laboratory, for their assistance in GB, Brasil. making many of the field and laboratory tests. Coulson, J. R. 1971. Prognosis for control of water We express our thanks to Jose A. Pastrana,· hyacinth by . Hyacinth Control J. 9: Douglas C. Ferguson,'· and Paul M. Marsh'" for 31-4. identifying the insect specimens, and to Joe V. Mad- DeLoach, C. J. 1975a. Evaluation of candidate ar- dox" for identifying the pathogen. We especially thropods for control of waterhyacinth: Studies in Argentina. P. 44-50. In Proc. Symp. Water Qual- thank Eugene G. Munroe" for contributing the entire ity Management through Biological Control, Gaines- section of this paper on the taxonomy of S. albigut- ville, FL, Jan. 29-31,1975. taUs and related species. 1975b. Identification and biological notes on the species of Neocltetina that attack Pontederiaceae in 15 Sameodes albjguttalis was released at 3 locations in the field in Florida on Sept. 22, 1977 by the U.S. Anny Corps of Argentina (Coleoptera: Curculionidae: Bagoini). En~ineers (G. R. Buckingham, Biological Pest Control Research Co]eopt. Bul!. 29: 257-66. Umt, Agric. Res. Serv., USDA, Gainesville. FL, pers. comm.). Releases were also made in the field in Australia in Oct. 1977 1976. N eocltetina bruclti, a biological control agent (K. L. S. Harley, Division of Entomology, CSIRO, Long Pocket of waterhyacinth: Host specificity in Argentina. Laboratories, Indooroopilly, Queensland, Australia, pers. comm.). Ann. Entomo\. Soc. Am. 69: 635-42. DeLoach, C. J., and H. A. 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