Interactions between the Parasitoid Rhopus nigroclavatus (Ashmead) (Hymenoptera: Encyrtidae) and its Mealybug Hosts Tridiscus sporoboli (Cockerell) and Trionymus sp. (Homoptera: Pseudococcidae)

This research investigated age-class-specific parasitism rates of the buffalograss mealybugs Tridiscus sporoboli (Cockerell) and Trionymus sp. by Rhopus nigroclavatus (Ashmead) (Hymenoptera; Encyrtidae), size class preference of this parasitoid, and mealybug–parasitoid interactions through choice and no-choice studies. In the no-choice studies, the mean rates of parasitism by R. nigroclavatus were 45, 20, 0, and 0%, respectively, for mealybugs adult female, third and fourth instars, first and second instars, and eggs. Choice studies indicated that rate of parasitism increased with host size. The mean rates of parasitism on mealybugs in the choice studies were 100% for adult females, 24% for third and fourth instars, 0% for first and second instars, and 0% for eggs. A second set of choice studies investigating mealybug/parasitoid behavior revealed that R. nigroclavatus oviposits in all post-egg mealybug age classes, but first and second instars were less often parasitized than older mealybugs.     

Factors affecting progeny production of Anaphes iole

Anaphes iole Girault(Hymenoptera: Mymaridae) is a native, solitaryegg parasitoid of Lygus spp.(Heteroptera: Miridae) in North America. Current research is considering factors thatmay optimize the in-vivo rearing of A.iole using Lygus hesperus Knight(Heteroptera: Miridae) as host. The effects ofhost density, day of oviposition and foodpresence, parasitoid age and mate presence onproduction of A. iole progeny weredetermined in this study. After exposingindividual parasitoids to host patches for 24h, the percentage of hosts containing a latestage A. iole pupa wassignificantly greater at a moderate hostdensity (41–70 eggs per patch) than at a lowdensity (10–40 eggs). But, no differenceswere detected between moderate and high density(71–100 eggs) or between high and low densitytreatments. More adult progeny were generatedby females (of variable age; 0–2 d old) onthe first day of oviposition rather than thesecond day, regardless of food presence. Progeny sex ratio was decidedly male-biased onthe second day. Female age (0 d vs 1 d old)had a marginal effect on production in 24 h; 0d old females tended to generate more adultprogeny than 1 d old females. Overall, thisresearch suggests that exposing newly-emerged,unfed, mated A. iole females to amoderate to high host density for 1 to 2 dcould lead to time-efficient production ofadult progeny in an in-vivo rearing system.     

Determination of Homalodisca coagulata (Hemiptera: Cicadellidae) egg ages suitable for oviposition by Gonatocerus ashmeadi, Gonatocerus triguttatus, and Gonatocerus fasciatus (Hymenoptera: Mymaridae)

Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) eggs 1–10 days of age were exposed to Gonatocerus ashmeadi Girault, Gonatocerus triguttatus Girault, and Gonatocerus fasciatus Girault (all Hymenoptera: Mymaridae) in no choice laboratory trials to investigate egg age utilization and to determine which egg ages are vulnerable to attack by these three parasitoids. The H. coagulata egg ages that were most suitable for oviposition by G. ashmeadi, G. triguttatus, and G. fasciatus were eggs 3, 4, and 2 days of age, respectively. Egg ages least suitable for parasitoid development were 6–10 days for G. ashmeadi (resulting in <50% parasitism), 1–2 and 7–10 days for G. triguttatus (resulting in <25% parasitism), and 3–10 days for G. fasciatus (resulting in <11% parasitism). Pooling parasitism data across all egg ages showed that parasitism by G. ashmeadi was 12.9 and 28.5% higher compared with G. triguttatus and G. fasciatus, respectively, and G. triguttatus resulted in 15.6% higher percentage parasitism compared with G. fasciatus. Egg age had a significant effect on the percentage of female G. ashmeadi offspring produced, but this was not significant for G. triguttatus, and low G. fasciatus parasitism prevented statistical analyses for comparisons. Results from tests where females were offered a choice for oviposition between eggs 1, 3, and 5 days of age demonstrated that G. ashmeadi and G. triguttatus showed no significant oviposition preference, while percentage parasitism by G. fasciatus was 29.4 and 7.4% higher when females were presented eggs 1 and 3 days of age, respectively, compared with eggs 5 days of age. Choice tests indicated that an overlap in egg age suitability for oviposition exists between G. ashmeadi, G. triguttatus, and G. fasciatus, and that interspecific competition for eggs 1, 2, and 3 days of age may occur in the field environment.     

Biological control of Lygus lineolaris by Peristenus spp. in strawberry

Peristenus digoneutis Loan (Hymenoptera: Braconidae) was introduced to the US for biological control of the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), and has since spread through much of the northeast. The purpose of this study was to determine if P. digoneutis and a native congener, Peristenus pallipes (Curtis), parasitize L. lineolaris in strawberry (where it is a key pest), and what factors relate to parasitism levels. During 1997–1999 we monitored parasitism on 17 strawberry farms in 14 counties in eastern and western New York State. We found that in eastern NY (where P. digoneutis has been established since the early 1990s), overall mean parasitism was 19.7% (ranging from 0 to 70%), mostly by P. digoneutis. Mean parasitism was significantly lower (12.3%, ranging from 0 to 58%) in western NY (where P. digoneutis was first recorded in 1999), and was mostly by P. pallipes. P. pallipes parasitism was significantly lower in eastern than western NY, suggesting the potential for competitive interaction with P. digoneutis. The insecticide regime of a farm was an important factor influencing parasitism rate, which was 5- to 6.5-fold higher on organic or casually sprayed farms than on intensely treated farms, though pest density under these three regimes was not significantly different. L. lineolaris density, and parasitism rate in nearby alfalfa and abandoned fields were also significant factors for parasitism in strawberry.     

Evaluation of cold-stored eggs of Dolycoris baccarum (Hemiptera: Pentatomidae) for parasitization by Trissolcus nigripedius (Hymenoptera: Scelionidae)

Trissolcus nigripedius Nakagawa (Hymenoptera: Scelionidae) is an egg parasitoid of Dolycoris baccarum L. (Hemiptera: Pentatomidae), a polyphagous insect pest of many crops including soybean. As a method for mass-rearing to augment the parasitoid, cold storage of host eggs were evaluated in the laboratory. After 0 (control), 8, 20, 60, 90, and 120 days of refrigeration, host eggs were given to adult female T. nigripedius. Host acceptance behaviors of the parasitoid, categorized as drumming, oviposition, and marking, on the refrigerated eggs and biological attributes of offspring were assessed. Most of the attributes examined were affected by the refrigeration of host eggs. But host eggs could be refrigerated for up to two months without significant change in emergence rate and sex ratio and with 90% of parasitism. In addition, the second generation of the parasitoid was not negatively affected at all. However, frozen eggs of D. baccarum can not be used for rearing the parasitoid since parasitism rate decreased to 44% on host eggs frozen for 8 days. Refrigeration of D. baccarum eggs could be useful for mass-rearing and augmentation of T. nigripedius to control D. baccarum without reduction in the quality of parasitoid’s progeny. Furthermore, refrigerated eggs could be supplemented in the field to boost the population of T. nigripedius since immature D. baccarum can not hatch after 20 days of refrigeration.     

Production of Anagrus epos Girault (Hymenoptera: Mymaridae) on Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) eggs

Anagrus epos Girault (Hymenoptera: Mymaridae) is a natural enemy candidate for a classical biological control program targeting the glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), in California. Little is known about the biology or ecology of A. epos when it utilizes GWSS eggs as a host. Here, we report the results of laboratory studies that describe the host age preference for oviposition, longevity of A. epos adults provided with different food sources, and developmental rates at six different constant temperature regimes. Anagrus epos is a gregarious parasitoid in GWSS eggs with up to 14 adults emerging from each GWSS egg. In choice and no-choice tests for oviposition, A. epos females successfully parasitized all developmental ages of GWSS eggs (1–8 days old). In choice tests, parasitism rates were significantly higher in 1-, 3-, 4-, and 5-day-old GWSS eggs than in 2-, 6-, 7-, and 8-day-old eggs. If provided with honey and water, honey only, water only, or no food or water, A. epos females lived on average 8.2, 4.7, 2.6, and 1.6 days, respectively. Anagrus epos required 294.1 degree-days above a lower temperature threshold of 12.4 °C to develop from egg to adult (eclosion). Our results provide baseline information useful in the development of an efficient parasitoid mass rearing program for A. epos release and evaluation in California.     

Integrating pesticide effects with inundative biological control: interpretation of pesticide toxicity curves for Anaphes iole in strawberries

We examined pesticide residue effects on the egg parasitoid Anaphes iole Girault (Hymenoptera: Mymaridae), an inundative biological control agent for Lygus hesperus Knight (Heteroptera: Miridae) in strawberries (Fragaria × ananassa Duchesne). Our objectives were to identify compatible pesticides, determine appropriate parasitoid release timings for minimizing harmful effects, and develop an approach for interpreting pesticide toxicity curves. Six insecticides, 2 acaricides and 6 fungicides were tested, and survivorship of adult A. iole exposed to foliar residues for 48 h, at 4–6 different times after pesticide application, was examined. A logistic function was developed for incorporating control mortality at each test date. Values for LT₅₀ (Lethal Time for 50% mortality) and mortalities on day 1 (initial mortality) and day 13 (estimated maximum time parasitoid releases can be delayed under extreme summer conditions) were estimated. In the study, insecticide residues proved to be the most toxic, followed by those from acaricides while most fungicides were least toxic. Among insecticides, fenpropathrin, bifenthrin and carbaryl caused the greatest mortality (estimated mortality on day 13 >75%). Residues of naled resulted in the least mortality (LT₅₀=3.2 days) followed by methomyl (LT₅₀=8.3 days) and malathion (LT₅₀=13.2 days). Estimated mortality = 12.3% on day 13 for the acaricide propargite and <1% for abamectin. For the fungicides benomyl, captan, myclobutanil and thiram, estimated mortality on day 1 was <1%, and for iprodione it was <6%, indicating compatibility with A. iole releases. For sulfur, LT₅₀=0, but the mortality decay curve was relatively flat (estimated mortality on day 13=13.6%). These results suggest possibilities for integrating A. iole releases with certain pesticide programs by appropriate timing of pesticide applications to minimize negative impacts.     

Non-target parasitism of the endemic New Zealand red admiral butterfly (Bassaris gonerilla) by the introduced biological control agent Pteromalus puparum

The New Zealand red admiral butterfly, Bassaris gonerilla (F.) (Lepidoptera: Nymphalidae), has been known as a non-target host for the introduced biological control agent Pteromalus puparum (L.) (Hymenoptera: Pteromalidae) for at least 35 years, but the level of parasitism has never been quantified. Pre-imaginal mortality in B. gonerilla was assessed over the southern summer of 2000/01 at six field sites in the Christchurch area of the South Island, New Zealand. Individual eggs and larvae were identified by tagging the stem of the Urtica ferox Forst.f. plant on which they were found and the fate of these individuals was checked weekly. These data were used to construct a partial life table for B. gonerilla. Egg mortality was very high (95%), with parasitism by an unidentified Telenomus sp. Haliday (Hymenoptera: Scelionidae) causing 57% mortality. Mortality in the larval and pupal stages increased at a constant rate with age and the major mortality factor was disappearance, which was assumed to be a result of predation and dispersal of larvae. The introduced biological control agent P. puparum parasitized 14% of B. gonerilla pupae sampled. However, parasitism by another exotic parasitoid, the self-introduced Echthromorpha intricatoria (F.) (Hymenoptera: Ichneumonidae), was even higher at 26%. A survey of pupal parasitism in three regions of New Zealand (Wellington, Christchurch, and Dunedin) revealed overall parasitism levels of 67% by E. intricatoria and 8% by P. puparum, but due to the difference in emergence times of B. gonerilla and its parasitoids, these are likely to be overestimates of percent parasitism. It is concluded that P. puparum has permanently enhanced mortality in B. gonerilla, but the level of mortality is low relative to egg parasitism by Telenomus sp., larval disappearance mortality, and pupal mortality due to E. intricatoria parasitism. To determine if this level of pupal parasitism has had population effects will require more data and the development of a population model for B. gonerilla.     

Aphelinus albipodus(Hymenoptera: Aphelinidae) andDiaeretiella rapae(Hymenoptera: Braconidae) Parasitism onDiuraphis noxia(Homoptera: Aphididae) Infesting Barley Plants Differing in Plant Resistance to Aphids

Russian wheat aphid,Diuraphis noxia(Mordvilko), as a pest of small grains, has prompted research into biological control and host plant resistance. In the presence of Russian wheat aphid, leaves of a susceptible barley (Morex) are curled and chlorotic and sustain large densities of this aphid, while leaves of a resistant barley (STARS-9301B) remain flat and green and sustain fewer aphids. Might parasitism of Russian wheat aphid byAphelinus albipodusHayat & Fatima andDiaeretiella rapaeMcIntosh be affected differently by these plant types? When presented the plants separately and based on parasitism rate relative to aphid density, the largerD. rapaewas more effective in parasitizing relatively high densities of aphids within curled leaves of Morex than relatively low densities of aphids on uncurled leaves of STARS-9301B. Parasitism byA. albipodusdid not significantly differ among the plants. When given a choice of plants, approximately equal rates of parasitism occurred on the two plant lines for both parasitoid species, and parasitism byD. rapaewas greater thanA. albipodus.These data indicate that using parasitoid size as an indicator of success in a physically restricted environment may be misleading, when considered in a plant environment responsive in several manners to aphids (chlorosis, curling, and ability to sustain Russian wheat aphid). We expect that use of resistant barley will result in decreased parasitoid abundance as aphid densities decrease. However, parasitism rates are expected to be approximately equal on resistant and susceptible barley. In this system, plant resistance and biocontrol are compatible management strategies.     

Plant-mediated decisions by an herbivore affect oviposition pattern and subsequent egg parasitism

Natural enemies are important mortality factors for herbivores and thus may influence herbivore population dynamics. In response to natural enemy pressure, herbivores can alter life history decisions, such as oviposition behavior, so that offspring are protected from natural enemies. One such strategy is to deposit eggs into structures where vulnerability to natural enemies is reduced or eliminated, i.e., use enemy-free space. The plant bug, Lygus lineolaris (Palisot de Beauvois), is native to North America and has a broad host range (>350 plant species), including crops. This bug’s eggs are attacked by a native parasitoid, Anaphes iole Girault, and parasitism levels vary greatly among host plant species. Weed hosts are critical to contemporary L. lineolaris life history because they serve as an ecological bridge from one crop growing season to the next. We investigated the egg distribution pattern of L. lineolaris on 11 host plant species (nine weeds and two crops), and parasitism by A. iole, to determine whether oviposition choices by L. lineolaris females protect their eggs from parasitism and to demonstrate the mechanism of this protection. Our results indicate that the reproductive structures of Erigeron annuus, as well as those of several other host plant species, provide a refuge from parasitism for most L. lineolaris eggs. This refuge is due to the deposition of host eggs deeper in plant tissue than the length of the ovipositor of A. iole. Also, overall parasitism levels were greater on non-Asteraceae host plant species compared with host plant species belonging to Asteraceae. Oviposition site choice by female bugs appears to be a selective strategy to take advantage of enemy-free space.     

The biology of Phymastichus coffea LaSalle (Hymenoptera: Eulophidae) under field conditions

The coffee berry borer (CBB) Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae) was accidentally introduced into México in 1978, and rapidly became the main pest of coffee. As an exotic pest, its management has been mainly based on biological control methods through the introduction of parasitoids from Africa. In this context, at the beginning of the present decade, the parasitoid Phymastichus coffea LaSalle (Hymenoptera: Eulophidae) was imported to Mexico. Since then, several studies have been carried out as part of the post introduction evaluation of this parasitoid. In this paper, information concerning the parasitism and life-cycle of P. coffea in coffee farms is presented with the objective of providing information that elucidates its role as a biological control agent. P. coffea showed highly significant preferences for allocation of two eggs per host, usually one female and one male. Both offspring are able to develop and reach the adult stage successfully. Lifespan of adults is 2–3 days only. The degree of parasitism by P. coffea was more than 95% at the three altitudes tested, when releases consisted of a ratio of 10 CBB:1 parasitoid. The median survivorship of CBB parasitized by this wasp was 13, 15 and 19 days at the low, medium and high altitude coffee zones, respectively. The parasitism by P. coffea was higher when parasitoid releases were carried out simultaneously with the CBB, and decreased with the time between host and parasitoid releases. We showed that using P. coffea at a density of 1 parasitoid per 10 hosts resulted in a 3- to 5.6-fold decrease in CBB damage to the coffee seeds when compared to the control. The importance and value of these results are discussed in terms of the use of P. coffea as a biological control agent of the CBB in Latin America.     

Are Lab-cultured <Emphasis Type="Italic">Anaphes iole</Emphasis> Females Strictly Proovigenic?

Anaphes iole Girault (Hymenoptera: Mymaridae) is a solitary egg parasitoid of Lygus bugs (Heteroptera: Miridae) in North America. Circumstantial evidence suggests that A. iole females are strictly proovigenic. This study was designed to determine if honey-fed A. iole females could in fact mature additional eggs if exposed to hosts for a few days then removed from hosts and held at 25 °C for 0, 3, or 6 days. Contrary to expectation, honey-fed A. iole females matured considerably more eggs when deprived of hosts for 3 or 6 days rather than 0 days. This research suggests that A. iole females are not strictly proovigenic. However, they do have proovigenic tendencies, since most females emerge with at least 71% of their potential fecundity.     

Host specificity of the egg pupal parasitoid Fopius arisanus (Hymenoptera: Braconidae) in La Reunion

Fopius arisanus is a polyphagous parasitoid of Tephritidae, which has been recently introduced to La Réunion Island as part of a classical biological control programme. We carried out laboratory experiments to assess the host specificity of this parasitoid, initially reared on Bactrocera zonata, and then offered for parasitization the eight local tephritid pest species. Naive or experienced parasitoid females were given tephritid eggs in no choice tests. Fopius arisanus females parasitize all fly species but parasitism varies with host species. No adult wasps emerge from Bactrocera cucurbitae and the survival of this species is only slightly affected by parasitism. Dissections show that the late instars of this fly may eliminate the parasitoid by encapsulation. When developing on Ceratitis capitata, Ceratitis rosa, Dacus ciliatus, Dacus demmerezi, and Neoceratitis cyanescens, parasitoid survival rate ranges from 10 to 25%. Bactrocera zonata and Ceratitis catoirii are the best hosts, yielding parasitoid survival rates of more than 70% with no premature mortality. The egg-larval mortality of C. capitata, C. rosa, D. ciliatus, and N. cyanescens, and the pupal mortality of D. demmerezi, are significantly increased by parasitism. The size of emerging adults is affected by host species and is correlated to pupal weight. Bactrocera zonata would be a favorable host to support routine colonization of F. arisanus for mass production of this parasitoid.     

Parasitism ofLygus lineolaris eggs onCoronilla varia,solanum tuberosum,and three host weeds in southeastern Québec

Parasitism ofLygus lineolaris (Palisot de Beauvois) eggs by three species ofMymaridae, Anaphes iole Girault,Erythmelus miridiphagus Dozier andPolynema pratensiphagum Walley and one species ofScelionidae, Telenomus sp., was investigated at Ste-Anne-de-Bellevue, Québec. The maximum level of field parasitism ofL. lineolaris eggs by individual species was 15.4, 53.8, 70.0 and 16,7%, respectively. Parasitoids were retrieved from eggs ofL. lineolaris inserted in stems and branches ofAmaranthus retroflexus L.,Chenopodium album L.,Coronilla varia L.,Rumex obtusifolius L. andSolanum tuberosum L. Amaranthus retroflexus andS. tuberosum sustained a large population ofL. lineolaris and egg parasitism was high enough to consider it as a potential control factor.      

The effects of mullein plants (Verbascum thapsus) on the population dynamics of Dicyphus hesperus (Heteroptera: Miridae) in tomato greenhouses

The response of Dicyphus hesperus Knight (Heteroptera: Miridae) to whitefly populations in tomato greenhouses was measured in the presence and absence of mullein (Verbascum thapsus L.) as an alternative host plant. The dynamics of the D. hesperus population on tomato (Lycopersicon esculentum Mill.) and on mullein plants were followed through an entire growing season. In houses with mullein plants, more predators occurred on mullein when whitefly density was low on tomato. A mark-release-recapture experiment where rabbit IgG was used as an external marker showed that D. hesperus adults moved from mullein plants to tomato plants. D. hesperus was always more abundant in houses with mullein than in the houses with tomato plants alone. Movements between tomato and mullein plants are discussed as a strategy to optimize predator foraging. The use of mullein as an alternative host plant may contribute to the establishment of D. hesperus and help to preserve the predator population when prey on tomato crops is scarce.     

Natural establishment of a parasitoid complex on Bactrocera latifrons (Diptera: Tephritidae) in Hawaii

Bactrocera latifrons (Hendel) (Diptera: Tephritidae) is the most recent of four tephritid fruit fly species accidentally introduced into Hawaii. Although parasitoids have been released against other tephritid fruit fly species and have shown partial success in Hawaii, no parasitoids were released until 2004 to suppress populations of B. latifrons. The present study was conducted to document the parasitoid complex that has naturally established against B. latifrons in Hawaii and to assess whether there is a need for improving the biological control of this species. Based on ripe turkeyberry (Solanum torvum Sw) fruit collections over three consecutive years B. latifrons was the dominant tephritid fruit fly infestating turkeyberry at all four sites surveyed, across three major islands in Hawaii. The overall percentage parasitism of B. latifrons ranged from a low of 0.8% (Hana, Maui) to a high of 8.8% (Kahaluu, Oahu). Five primary parasitoid species were recovered from individually held B. latifrons puparia: Fopius arisanus (Sonan), Psyttalia incisi (Silvestri), Diachasmimorpha longicaudata (Ashmead), D. tryoni (Cameron), and Tetrastichus giffardianus Silvestri. F. arisanus was the predominant parasitoid at three of the four sites. Low levels of parasitism suggest that there is a need to improve biological control of B. latifrons, to minimize chances of this species causing economic impacts on crop production in Hawaii. We discuss the possibility of improving biological control of B. latifrons through augmentative releases of F. arisanus or introduction and release of specific and efficient new parasitoid species.     

Distribution, host specificity, and overwintering of Celatoria bosqi Blanchard (Diptera: Tachinidae), a South American parasitoid of Diabrotica spp. (Coleoptera: Chrysomelidae: Galerucinae)

The genus Diabrotica (Coleoptera: Chrysomelidae) includes a great number of pest species, including some of the most important crops pests of the Americas. However, only five parasitoid species have been recorded for it. The parasitoid Celatoria bosqi Blanchard was the first parasitoid described from Diabrotica spp. in South America, where substantial parasitism has been observed. C. bosqi has been collected almost throughout the South American distribution of its main host, Diabrotica speciosa (Germar), in an area that includes temperate and tropical lowlands, and semiarid to humid highlands. Three Diabrotica species were found to host the parasitoid, D. speciosa (Germar), Hystiopsis sp., and Diabrotica viridula (F.), with a total parasitism of 2.60, 5.55, and <0.02%, respectively. Laboratory experiments with field beetles and puparia, reared in the laboratory, indicate that C. bosqi overwinters obligatorily in overwintering adult host beetles, remaining quiescent in its live host below developmental temperatures. Based on the known climatic range of C. bosqi, and its requirement of adult overwintering hosts, a potential distribution in North America is projected.     

Establishment of papaya banker plant system for parasitoid, Encarsia sophia (Hymenoptera: Aphilidae) against Bemisia tabaci (Hemiptera: Aleyrodidae) in greenhouse tomato production

The silverleaf whitefly, Bemisia tabaci biotype B (Gennadius) (Hemiptera: Aleyrodidae), is a key pest of tomato (Solanum lycopersicum L.) and other vegetable crops worldwide. To combat this pest, a non-crop banker plant system was evaluated that employs a parasitoid, Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphelinidae) with whitefly, Trialeurodes variabilis (Quaintance) (Hemiptera: Aleyrodidae), as an alternative host for rearing and dispersal of the parasitoid to the target pest. (a) Multi-choice and no-choice greenhouse experiments were conducted to determine host specificity of T. variabilis to papaya (Carica papaya L.) and three vegetable crops including tomato, green bean (Phaseolus vulgaris L.), and cabbage (Brassica oleracea L.). The result showed that papaya was an excellent non-crop banker plant for supporting the non-pest alternative host, T. variabilis, whose adults had a strong specificity to papaya plants for feeding and oviposition in both multi-choice and no-choice tests. (b) The dispersal ability of E. sophia was investigated from papaya banker plants to tomato and green bean plants infested with B. tabaci, as well as to papaya control plants infested with T. variabilis; and (c) the percent parasitism by E. sophia on T. variabilis reared on papaya plants and on B. tabaci infested on tomato plants was also evaluated. These data proved that E. sophia was able to disperse at least 14.5 m away from papaya plants to target tomato, bean or papaya control plants within 48–96 h. Furthermore, E. sophia was a strong parasitoid of both T. variabilis and B. tabaci. There was no significant difference in percent parasitism by E. sophia on T. variabilis (36.2–47.4%) infested on papaya plants or B. tabaci (29–45.9%) on tomato plants. Thus, a novel banker plant system for the potential management of B. tabaci was established using papaya as a non-crop banker plant to support a non-pest alternative host, T. variabilis for maintaining the parasitoid to control B. tabaci. The established banker plant system should provide growers with a new option for long-term control of B. tabaci in greenhouse vegetable production. Ongoing studies on the papaya banker plant system are being performed in commercial greenhouses.     

Effects of local vegetation and plantation age for the parasitoid Asecodes mento– a biocontrol agent in organic strawberry fields

Abstract The parasitoid Asecodes mento (Walker, 1839) (Hymenoptera: Eulophidae) is the most important biocontrol agent of the strawberry leaf beetle Galerucella tenella (L.) (Coleoptera: Chrysomelidae) in northern Europe. Here, I investigated whether natural parasitism in organic strawberry plantations was affected by the presence of the alternative host plant meadowsweet (Filipendula ulmaria), and whether parasitism rates differed between plantations of different ages (6 to 79 years). I also investigated whether parasitoid brood size, body size and sex ratio differed between the two host plants in the field. Parasitism was very low (0%) in newly established plantations and increased to a plateau (～40%) in fields where strawberries had been grown for approximately 20 years or longer. Such an extended colonization process is unacceptable for commercial growers. It would thus be desirable to find a method to catalyze parasitoid population buildup in young plantations. Parasitoid brood sizes were larger in beetles collected from meadowsweet, while body size and sex ratio did not differ between parasitoids collected from the two plants. These findings suggest that meadowsweet can export parasitoids to neighboring strawberry fields. Although this is a possibility, I did not find any significant differences in parasitism rates between isolated strawberry fields and fields adjacent to meadowsweet stands, indicating that effects of local vegetation are small on parasitism rates. Releasing parasitoids in newly established strawberry plantations may be a better strategy for quickly obtaining high parasitism than intercropping with meadowsweet.     

Egg load of lab-cultured <Emphasis Type="Italic">Anaphes iole</Emphasis> and effects of mate presence and exposure time on load depletion

Anaphes iole Girault (Hymenoptera: Mymaridae) is a solitary egg parasitoid of Lygus bugs (Heteroptera: Miridae) in North America. This research considered factors that might impact the egg load of lab-cultured A .iole females, reared from Lygus hesperus Knight egg patches. The following hypotheses were tested: (1) egg load was related to body size and not affected by female age, and (2) egg load depletion was not affected by mate presence and time (in days) that females were exposed to host patches. Initial egg load averaged 48 mature eggs and no immature eggs were detected in the ovarioles of dissected females. Egg load was neither related to body size (hind tibia or forewing length) nor affected significantly by age (0, 1 or 2days old honey-fed females). Mate presence (females with or without males) and exposure time (1, 3 or 5days on the same host patch) had no effect on egg load depletion. Females usually depleted most of their egg load within 24h. From 86 to 92% of females contained less than six mature eggs and no immature eggs after 1, 3 or 5days of exposure to host patches. The results of this study suggest that A. iole females are certainly pro-ovigenic and initial egg load does not correlate with body size or age. Since mated and unmated females deplete most of their egg load in 24h, time-efficient production of progeny may result when ovipositing parasitoids are exposed to suitable hosts for just a few days.The United States Government has the right to retain a non-exclusive, royalty-free license in and to any copyright of this article. This article reports the results of research only. Mention of a commercial or proprietary product does not constitute an endorsement of the product by the United States Department of Agriculture.