Egg Parasitism Rates Research Articles

Field Control Effect of Telenomus remus Nixon and Trichogramma chilonis Ishii Compound Parasitoid Balls against Spodoptera frugiperda (J. E. Smith).

Although the release of egg parasitoids has proven to be an effective strategy for the control of the fall armyworm (FAW), a single egg parasitoid, however, has exposed some deficiencies in practice, and it is worthwhile to explore whether the combination of multiple parasitoid species released can be used to control FAW by adopting an inter- or intra-specific relationship. In this study, we released compound parasitoid balls of Te. remus and Tr. chilonis in maize fields to explore the effects of combinations in different proportions of these two egg parasitoids on the control of the FAW. The results showed that the release of compound parasitoid balls improved the control effect on the FAW compared to the release of only Te. Remus (100%) and only Tr. Chilonis (100%). The treatments released with compound parasitoid balls significantly increased the egg parasitism rate against the FAW, reduced its populations, and alleviated its damage to maize as compared to the treatment with only Tr. chilonis (100%) released, whereas there was no significant difference in the egg parasitism rate and FAW populations between the treatments with the release of only Te. remus (100%) and that of compound parasitoid balls. Among the compound parasitoid balls with different proportions of egg parasitoids, the treatment with 80% Te. remus and 20% Tr. chilonis and that with 20% Te. remus and 80% Tr. chilonis could still retain more than 50% of the control effect against the FAW after 15 days of release and given the higher cost of production of Te. Remus, our results suggested that the combination of 20% Te. Remus and 80% Tr. Chilonis is a more cost-efficient ratio for the control of the FAW. Our findings may provide a new perspective for the sustainable control of the FAW.

Species diversity and abundance of parasitoids of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) from South Sumatra, Indonesia

Abstract. Herlinda S, Suwandi S, Irsan C, Adrian R, Fawwazi F, Akbar F. 2023. Species diversity and abundance of parasitoids of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) from South Sumatra, Indonesia. Biodiversitas 24: 6184-6190. The parasitoid species attacking Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) have never been reported from South Sumatra. The objectives of this research were to identify and analyze the species diversity of egg and larval parasitoids of S. frugiperda and to determine their abundance in corn fields from South Sumatra. Surveys were carried out in Ogan Komering Ilir District, Ogan Ilir District, Muara Enim District, and Palembang City. The results showed that fourteen species of parasitoids were found attacking eggs and larvae of S. frugiperda in South Sumatra. Two species were egg parasitoids (Telenomus remus (Nixon) and Trichogramma sp.), and 12 species of larval parasitoids (Chelonus formosanus Sonan, Chelonus oculator F., Chelonus annulipes Wesm., Chelonus cautus (Cresson), Microplitis manilae Ashmead, Microplitis marshallii Kokujev, Euplectrus corriemoreauae Hansson, Compsilura concinnata (Meigen), Sarcophaga sp., Macrocentrus sp., Exorista sp., and Megaselia sp.). The most abundant species of the parasitoids found was T. remus. The highest species diversity was found in Muara Enim District. The number of parasitoid species was greater in the dry season compared to the rainy season. Egg parasitism rates were significantly higher at the corn vegetative stage (59.03%) compared to the generative stage (53.56%).

Augmentative biological control for squash bug (Hemiptera: Coreidae) using the egg parasitoid, Hadronotus pennsylvanicus (Hymenoptera: Scelionidae).

The squash bug, Anasa tristis (De Geer) (Hemiptera: Coreidae), is a serious pest of cucurbit crops across the United States. Conventional growers commonly use broad-spectrum insecticides to manage squash bugs, however organic growers lack these effective chemical tools and must rely on alternative management strategies. Biological control of A. tristis is largely understudied, specifically the potential of natural enemy, Hadronotus pennsylvanicus (Ashmead) (Hymenoptera: Scelionidae), as an augmentative biological control agent. For this reason, we performed early-season field releases of H. pennsylvanicus on organic farms in southeastern Virginia to test if this would improve A. tristis egg parasitism. We chose organic vegetable farms growing summer squash (Cucurbita pepo L.) as release sites and nearby Virginia Tech Agricultural Research Extension Centers (AREC) as no-release sites. Parasitoids were reared in the lab and deployed as parasitized egg masses (~2-3 females wasps/plant) in June 2020 and 2021. Before parasitoid deployment, host eggs collected from release and no-release sites displayed low levels of H. pennsylvanicus parasitism in 2020 (<21%) and 2021 (<8%). In both years, the percentage of A. tristis eggs parasitized within 2 weeks post deployment was significantly greater at release sites (~60%) than at no-release sites (~14%). High rates of H. pennsylvanicus parasitism (>72%) were further observed at release sites 4, 6, 8, and 10 weeks following parasitoid deployment. Our study demonstrates that releases of lab-reared H. pennsylvanicus can increase A. tristis egg parasitism rates and subsequently decrease successful nymph hatch rates in early summer squash plantings.

Postrelease assessment of Oobius agrili (Hymenoptera: Encyrtidae) establishment and persistence in Michigan and the Northeastern United States.

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is an invasive woodboring pest of ash trees (Fraxinus sp.) in North America. Among the Asiatic parasitoids being released for the management of EAB in North America, Oobius agrili Zhang and Huang (Hymenoptera: Encyrtidae) is the only EAB egg parasitoid. To date, more than 2.5 million O. agrili have been released in North America; however, few studies have examined its success as a biological control agent of EAB. We conducted studies to assess O. agrili establishment, persistence, spread, and EAB egg parasitism rates in Michigan at the earliest release sites (2007-2010), as well as at more recent release sites (2015-2016) in 3 Northeastern United States (Connecticut, Massachusetts, New York). In both regions, we documented successful O. agrili establishment at all but one release site. In Michigan, O. agrili has persisted at release sites for over a decade and spread to all control sites located 0.6-3.8 km from release sites. Overall, EAB egg parasitism ranged from 1.5% to 51.2% (mean of 21.4%) during 2016-2020 in Michigan and from 2.6% to 29.2% (mean of 16.1%) during 2018-2020 in the Northeastern states. Future research efforts should focus on factors affecting the spatiotemporal variation in EAB egg parasitism rates by O. agrili, as well as its potential range in North America.

Wildflower plantings have mixed effects on insect herbivores and their natural enemies

Flower strips are advocated as a strategy to promote beneficial insects as well as the services they deliver to adjacent crops. Flower strips have, however, often been developed separately for pollinators and natural enemies and, additionally, little consideration has been given to effects on insect herbivores. We sampled insect herbivores, their natural enemies and parasitism of pest eggs using vacuum sampling, sticky cards and egg cards in nine pairs of bee-attractive wildflower plantings and control field borders, as well as in adjacent tomato and watermelon crop fields in Yolo County, California 2015–2016. Control field borders had a higher total number of herbivores on sticky traps than did wildflower plantings, a pattern that was driven by more aphids, hoppers, psyllids and whiteflies, whereas wildflower plantings had more lace bugs and Lygus bugs. The total number of herbivores in the adjacent crop fields did not differ between treatments, but there were more leaf beetles near (at 10 m but not 50 m from) wildflower plantings. Control field borders had a higher total number of predators, driven by more big-eyed bugs, lady beetles and minute pirate bugs, whereas spiders were more common in wildflower plantings. The total number of predators in adjacent crop fields was, however, higher in those next to wildflower plantings, which was driven by more minute pirate bugs. Parasitoid wasps were more common in wildflower plantings and at 10 m but not 50 m into adjacent crop fields. Stink bug egg parasitism rate did not differ between treatments, either in the borders or in the crop fields. In conclusion, wildflower plantings clearly affect the insect herbivore and natural enemy community, but do so in a highly taxon-specific manner, which can lead to both positive and negative outcomes for pest control as a result.

Field evaluation of Trichogramma strains collected from Myanmar for biological control of Asian corn borer, Ostrinia furnacalis (Guenée) (Lepidoptera: Crambidae) and sustainable maize production

Trichogramma (Hymenoptera: Trichogrammatidae) egg parasitoids are successfully used for biological control of Asian corn borer, Ostrinia furnacalis (Guenée) in China. This pest has become increasingly problematic in Myanmar and surrounding countries. To determine the optimal number of releases, release density and select the most effecive parasitoid, two strains of Trichogramma ostriniae (Pang and Chen) and one Trichogramma dendrolimi (Matsumura), originating from Myanmar, were assessed under field-cage conditions in 2020–2021. Three release densities, 50,000 wasps/ha (low), 100,000 wasps/ha (medium) and 200,000 wasps/ha (high), were tested with three releases at weekly intervals during tasseling stage. The highest egg parasitism rate was achieved by T. ostriniae from Yatsawk, Southern Shan State (overall 89%), followed by T. dendrolimi from Yatsawk and T. ostriniae from Taungyi (67%). The kernel weight of maize plots treated with the T. ostriniae from Yatsawk was 1.2–1.4 times higher than values for the other two tested strains and significantly increased yield by 60% over control plots. Trichogramma ostriniae from Yatsawk overall showed the best performance, and may be considered the most promising strain for biological control of O. furnacalis in Myanmar. Two- and three-inundative releases substantially reduced plant damage (60–80%) and yield loss (50%) over control plots. The highest cost-benefit ratio (1:31) was found for two releases of the medium release density. Two releases with either medium or high release density was optimal to achieve high yield and best net return. Our results facilitate the initiation of a biological control program to improve maize production in Myanmar.

Oviposition by a lycaenid butterfly onto old host parts is adaptive to avoid interference by conspecific larvae.

Oviposition site selection by herbivores can depend not only on the quality of host resources, but also on the risk of predation, parasitism and interference. Females of the lycaenid butterfly Arhopala bazalus (Lepidoptera) lay eggs primarily on old host foliage away from fresh growth, where larval offspring live and feed. Resource availability of young host leaves seems not to affect the oviposition site preference by the females. To clarify the adaptive significance of A. bazalus oviposition behavior on old foliage, we tested three hypotheses: eggs on fresh foliage are (1) easily dropped during rapid leaf expansion (bottom-up hypothesis), (2) more likely to be attacked by egg parasitoids (top-down hypothesis), and (3) frequently displaced or injured by other herbivores (interference hypothesis). In field surveys, rates of egg dropping and parasitism by egg parasitoids were not significantly different between fresh and old host parts. However, the portions of fresh leaves on which A. bazalus eggs had been laid were cut from shoots on which conspecific larvae fed. Laboratory experiments demonstrated that eggs on young leaves were displaced in the presence of conspecific larvae and we observed that fifth instar larvae actively displaced conspecific eggs by feeding on the surrounding leaf tissue. These findings indicate that eggs laid on fresh leaves are at risk of being displaced by conspecific larvae, and support the interference hypothesis. Larval behavior is a likely evolutionary force for A. bazalus to lay eggs apart from larval feeding sites on the host plant.

Damage, distribution and natural enemies of invasive fall armyworm Spodoptera frugiperda (J. E. smith) under rainfed maize in Karnataka, India

Fall armyworm, Spodoptera frugiperda (J.E. Smith), is a polyphagous pest invaded India and seriously threatened maize and other crops. The detailed information on its occurrence and damage severity in the invaded regions are limited. In this study, we assessed the occurrence, incidence and damage severity of fall armyworm in 126 maize fields in 10 districts of Karnataka during the rainfed condition. Further, potential co-occurrence of this pest with native stem borers and its natural enemies explored to tackle this pest. Survey reports revealed that the fall armyworm was well distributed across the maize growing regions of Karnataka with 44–100% field infestation. The damage incidence of S. frugiperda was 22.13–46.83% with damage severity 0 to 4.9 on the 0 to 9 scale. The larval count was 0.93 ± 0.17 to 3.07 ± 0.58 per 10 plants across the locations. The co-occurrence of S. frugiperda with the native maize stem borers, Chilo partellus (Swinhoe) and Sesamia inferens (Walker) was less than 5% of the plants. It shows that S. frugiperda had dominated the native stem borers causing significant damage to maize. This study found five parasitoids parasitizing the egg, egg-larval, larval and larval-pupal stages of S. frugiperda. Trichogramma chilonis Ishii and Telenomus remus Nixon egg parasitism rates were 15.81–23.87% and 5.44–8.78%, respectively. The larval parasitoids caused 9.18% parasitism of S. frugiperda larvae. Trichogramma chilonis appeared as a major natural enemy. These data provide an important baseline for the development of sustainable management strategies for S. frugiperda.

No significant effects of insecticide use indicators and landscape variables on biocontrol in field margins

Insecticides are used widely to manage pests, but they may cause mortality in natural enemy populations and non-target prey. On the other hand, resources provided by the landscape – often associated with semi-natural habitat – may enhance natural enemy communities. While there is substantial information on how insecticide use and semi-natural habitats influence biocontrol in crop fields, little is known about how local insecticide use interacts with landscape variables to govern natural biocontrol in field margins. In this 2-year study we assessed predation and parasitism rates of eggs of the cabbage moth (Mamestra brassicae) on potted cabbage plants in field margins adjacent to 20 organically managed fields and 18 conventionally managed fields We analysed egg predation and parasitism rates in field margins using three predictors for insecticide use: (i) farming system (organic or conventional), (ii) frequency of insecticide use in the adjacent focal fields, and (iii) estimated insecticide use quantity within a radius of 1 km from the sampling sites. Insecticide use included foliar or soil-applied applications, including mineral oils. Landscape variables were used as covariables to account for landscape effects. Mean predation and parasitism rates were 14 % and 6%, respectively. There were no significant associations between predation and parasitism rates in field margins with insecticide use in the adjacent field or the wider landscape. Our findings suggest that field margins can be valuable habitats for natural enemies in agricultural landscapes, irrespective of the insecticide use intensity at the local and landscape scale.

Long-term decline in the parasitism rate of passionvine hopper eggs (Scolypopa australis)

Passionvine hopper, Scolypopa australis (Walker) (Hemiptera: Ricaniidae), (PVH) is an introduced pest of kiwifruit grown in New Zealand. Two aphelinid egg parasitoids, Centrodora scolypopae Valentine and Ablerus sp., are thought to be its most important natural enemies. Rates of egg parasitism measured during 2010–2015 in the Bay of Plenty region and in a wider survey of the North Island of New Zealand in 2015 were ≤ 10% compared with medians of about 30–50% for historical estimates. PVH eggs laid in bracken, a favored host plant, in 2015 and 2019 were parasitized at about half the rate or less than indicated by measurements made 20, 35–38 and 57 years ago. The apparent decline may have been the result of asynchrony between one or both egg parasitoids and PVH associated with warmer summer and autumn temperatures. Further work is needed to clarify the role of each parasitoid in PVH population dynamics.

Use of Flowering Plants to Enhance Parasitism and Predation Rates on Two Squash Bug Species Anasa tristis and Anasa armigera (Hemiptera: Coreidae).

A two-year study evaluated the effect of a flowering border of buckwheat Fagopyrum esculentum Moench on rates of egg parasitism, egg predation and adult parasitism on two squash bug species, Anasa tristis (DeGeer) and Anasa armigera Say, by comparing rates in squash fields with and without a flowering border. Furthermore, we evaluated whether there was an edge effect by comparing parasitism and predation rates in plots located in the corner of a squash field with plots located in the center of a squash field for fields with and without a flowering border. The egg parasitism rates were not affected by either treatment (flowering border or control) or plot location (edge or center). Anasa armigera egg masses only accounted for 4.3% of the total egg masses collected. The egg parasitism rates increased gradually throughout the season, peaking in the last week of August in 2017 at 45% for A. tristis egg masses. The most common egg parasitoid recovered was Gryon pennsylvanicum (Ashmead) followed by Ooencyrtus anasae (Ashmead). Adult parasitism was not affected by treatment, but A. tristis adult parasitism rates were higher in plots located on the edge of squash fields compared with plots located in the center of squash fields in 2016. Since adult parasitoid, Trichopoda pennipes (Fabricius) flies were observed visiting buckwheat flowers, future studies could explore the possibility that the flowering buckwheat may have a more impact on adult parasitism if there was a greater distance between fields with and without a flowering border.

Phenology of sugarcane leaf hopper Pyrilla perpusilla (Walker) (Homoptera: Lophopidae) and its natural enemies in a crop island scenario

Population dynamics of sugarcane leaf hopper Pyrilla perpusilla (Walker) (Homoptera: Lophopidae) and its natural enemies, namely the egg parasitoid Parachrysocharis javensis Girault (= Tetrastichus pyrillae Chrawford) (Hymenoptera: Eulophidae), nymphal parasitoid Dryinus pyrillae (Kieffer) (= Lestodryinus pyrillae Kieffer) (Hymenoptera: Dryinidae) and entomophathogenic fungus Hirsutella citriformis Speare (Ascomycota: Ophiocordycipitaceae) were studied in sugarcane germplasm maintained as a crop island. During the three-year (2010–12) study period, germplasm was planted in January/February each year, and fortnightly observations of pyrilla and natural enemy abundance were recorded. In all three years, pyrilla populations began in May, peaked during September–October and declined thereafter. The proportion of adults in relation to that of nymphs was high in the beginning, decreased progressively and increased towards the end of the crop season. Pyrilla populations differed significantly among the fortnights and years. Activity of P. javensis began early in the crop season and its parasitism rates continued to reach high levels until September–October. Parasitism rates among eggs masses were the lowest in 2010 (83.3%) and highest in 2011 (96.1%). Parasitism rates within egg masses differed significantly among the three years with the lowest (36.3%) in 2010 and highest (41.4%) in 2011. The occurrence of D. pyrillae began around June and its intensity reached a peak during October–December. The mean parasitism rate of 3.1% in 2010 declined to 2.6% in 2011 and 2.1% in 2012. Field pathogenicity of H. citriformis, which began in August and ended in December, varied among the three study years with higher infection rates in adults than in nymphs. The overall infection rates increased in successive years with a significant two-fold surge in 2012 (25.4 ± 34.1%) as compared to that in 2010 (12.5 ± 16.5%). Simple and multiple correlation analysis of pyrilla populations vs. natural enemy activity showed that egg parasitism rates alone were significantly and positively related to pyrilla abundance. Similar analysis with weather parameters indicated their indistinct influence on both pyrilla and natural enemy populations.

Field parasitism and host specificity of Oobius primorskyensis (Hymenoptera: Encyrtidae), an egg parasitoid of the emerald ash borer (Coleoptera: Buprestidae) in the Russian Far East

Oobius primorskyensis Yao and Duan (Hymenoptera: Encyrtidae) is a recently described egg parasitoid of the emerald ash borer (EAB), Agrilus planipennis Fairmaire, from the Russian Far East. To support the potential introduction of this new parasitoid for biocontrol of EAB in North America, we surveyed EAB eggs on infested green ash (Fraxinus pennsylvanica Marsh) trees in the Russian Far East and documented the rate of EAB egg parasitism by O. primorskyensis. After establishing quarantine colonies of O. primorskyensis in the United States, we tested the parasitoid against eggs of 30 taxa of insects, mostly native North American wood-boring beetles in the families Buprestidae and Cerambycidae plus one unidentified weevil, one predatory coccinellid, one pentatomid and one moth. Field observations showed that EAB egg parasitism rate ranged from 23 to 44% in the Russian Far East and O. primorskyensis was the only egg parasitoid recovered from the parasitized eggs collected there. Quarantine testing showed that O. primorskyensis attacked seven out of nine Agrilus species, but not any of the other non-target species tested. Percentage parasitism of A. anxius (40%) and A. cephalicus (30%) was comparable to parasitism of their corresponding EAB (positive) control (29–30%). However, percentage parasitism of the other five attacked species (A. bilineatus, A. egenus, A. fallax, A. macer, and A. oblongus) were significantly less (4–17%) than for the EAB control (60–90%). These results indicate that the host specificity of O. primorskyensis may be limited to species phylogenetically closely related to EAB, such as those in the genus Agrilus. Additional testing is needed to determine whether the eggs of other buprestid genera are utilized by the species as well.

Enemy-free space is important in driving the host expansion of a generalist herbivore to an inferior exotic plant in a wetland of Yangtze Estuary

Novel interactions between exotic plants and native herbivores can be driven by multiple ecological and evolutionary processes, but the underlying mechanisms have rarely been explored from a multitrophic perspective. In this study, we examined the effects of host plant quality and natural enemies on the host plant use of a native generalist Laelia coenosa, which was recently known to expand its host range from indigenous Phragmites australis to invasive exotic Spartina alterniflora in the wetlands of Yangtze Estuary, China. A field population survey showed that larval density of L. coenosa was significantly higher in S. alterniflora monocultures (SM) than in P. australis monocultures (PM) and patches in S. alterniflora-dominated communities (PIS). Nonetheless, an indoor rearing experiment suggested feeding on S. alterniflora significantly reduced larval growth rate, cocoon weight, adult lifespan and female lifetime fecundity of L. coenosa in comparison with P. australis. Despite an induced feeding preference in 5th instar larvae, both 1st and 3rd instar larvae of L. coenosa significantly preferred leaves of P. australis over S. alterniflora. These results contradicted the field population survey. Subsequent field experiments showed larval mortality of L. coenosa significantly increased in habitats with SM < PIS < PM. The same trend was observed in the egg parasitism rate of L. coenosa by a specialized parasitoid Telenomus laelia. Generally, our study suggests that the enemy-free space provided by the invasive S. alterniflora is important in driving the host expansion of L. coenosa to this inferior exotic plant.

Ant-related oviposition is not associated to low parasitism of the myrmecophilous butterfly Allosmaitia strophius in an extrafloral nectaried shrub

In Lycaenidae-ant mutualisms, ovipositing females select plants based on the presence and/or species of ants in order to maximize survival rates of immatures. The ants are supposed to protect the immatures from parasitoids, but there is large variation in the protection provided. Here, we experimentally investigated whether the occurrence of the facultative myrmecophilous Allosmaitia strophius (the dominant species in our study system) was ant-related. The parasitism rates of immatures collected in the field and reared in the laboratory were also investigated. Stems of the extrafloral nectaried shrub Peixotoa tomentosa were designated as either ant-present (control) or absent (treated). The occurrence of A. strophius on ant-present stems was five times greater than on treated stems. Most eggs and larvae were associated with Camponotus blandus and Ectatomma tuberculatum, two aggressive ant species in the Brazilian savanna. Egg parasitism rate was 9%, and all the parasitized eggs were on ant-present stems. Pupal parasitism on ant-present and ant-absent stems was 25.6% and 7%, respectively. The higher parasitism rate in the presence of ants might also have been density-dependent, because caterpillars were more abundant in ant-present stems. Tropical lycaenids are frequently found in association with patrolling ants. Nevertheless, there is growing evidence that parasitism is higher in the presence of ants, owing to caterpillar's density-dependent effects in plants with ants, and/or to the weak lycaenid-ant associations. This indicates that the offspring of myrmecophilous lycaenids may not benefit, at least in terms of lower parasitism, by living with ants.

Seasonal Occurrence and Interspecific Interactions of Egg Parasitoids of Megacopta cribraria (Heteroptera: Plataspidae) in Japan

We conducted a field study to determine seasonal egg parasitism rates of the kudzu bug Megacopta cribraria (F.) on the kudzu plant, Pueraria montana (Lour.) Merr. var. lobata (Willd.) Maesen et Almeida ex Sanjappa and Pradeep, in Tokyo, Japan, during the period from May 2014 to September 2014. The eggs of M. cribraria per 1 m2 of kudzu at four locations in Tokyo were collected weekly and parasitism rates were assessed. Eggs of M. cribraria were laid on the kudzu plant from May to September. Megacopta cribraria eggs were parasitized by two parasitoid species, Paratelenomus saccharalis (Dodd) and Ooencyrtus nezarae Ishii. Paratelenomus saccharalis first appeared in May, and its parasitism rates peaked in July and September. Ooencyrtus nezarae first appeared in June and its parasitism rates peaked in July. Except for one location which could not be statistically analyzed because of the small sample size, occurrence of parasitism by P. saccharalis and O. nezarae in M. cribraria egg masses was independent at one location and positively associated at two locations, suggesting that the use of host egg masses by P. saccharalis and O. nezarae is not mutually exclusive. Parasitism rates by P. saccharalis and O. nezarae were significantly lower for egg masses parasitized by both species than for those parasitized by a single species. The proportion of males among O. nezarae progeny was significantly higher for egg masses parasitized by O. nezarae together with P. saccharalis than for those parasitized by O. nezarae alone. These results suggest that parasitism of host egg masses by the two species is influenced by their interspecific interactions.

Pengaruh ketiadaan inang terhadap tanggap reproduksi Trichogrammatoidea armigera Nagaraja dan Trichogramma japonicum Ashmed (Hymenoptera: Trichogrammatoidea) dan implikasinya terhadap penerimaan inang

Trichogrammatoidea armigera and Trichogramma japonicum are polyphagous egg parastioids, that are important as natural enemies. The objective of this research was to study the effect of host deprivation on reproductive capacity of T. armigera and T. japonicum. This study consists of 8 treatments, host deprivation : 0 hour, 1 hour, 2 hours, 3 hours, 6 hours, 12 hours, and 48 hours. Host were replaced every 24 hours. Results showed there are difference with respect of how the two parasitoids respond to the treatment. Deprivation of host for 3 hours in T. armigera resulted in the increase of egg production and parasitism rate. After 12 and 24 hours of not encountering any hosts, the numbers of eggs produced drastically decreased. Treatment on T. japonicum resulted in the reaction of fecundity and parasitism rate overall. Forty eight hours of host deprivation resulted in death of both parasitoids species within 2 days. None of the parasitoids seems to produce any egg.

Assessment of Trichogramma japonicum and T. chilonis as Potential Biological Control Agents of Yellow Stem Borer in Rice.

Two species of Trichogramma wasps were assessed for their effectiveness against yellow stem borer Scirpophaga incertulas. A laboratory cage test with T. japonicum and T. chilonis showed that both species parasitized yellow stem borer egg masses at 60.0% ± 9.13% and 40.7% ± 7.11%, respectively, with egg parasitism rates of 15.8% ± 22.2% for T. japonicum and 2.8% ± 5.0% for T. chilonis. Once the host eggs were parasitized, emergence rates were high for both species (95.7% ± 0.12% for T. japonicum and 100% for T. chilonis). In paddy field trials, the two Trichogramma species were released at three densities (50,000/ha, 100,000/ha and 200,000/ha) in Southwestern China. Egg mass parasitism was 9% ± 7.7% for T. japonicum and 15% ± 14.1% for T. chilonis, and again only a relatively small fraction of eggs was successfully parasitized. No clear conclusion could be drawn on the most efficient release rate as no significant differences were found among the three release rates. A comparison of field-collected T. japonicum with T. japonicum and T. chilonis mass reared on Corcyra cephalonica showed significantly larger body size and ovipositor length in field-collected wasps, suggesting potentially higher effectiveness on yellow stem borer eggs after at least one generation on the target host. Factors contributing to the low field parasitism rates are discussed.

Natural parasitism of the second generation European corn borer eggs Ostrinia nubilalis (Hübner) (Lepidoptera, Pyralidae) by Trichogramma spp. in sweet corn fields in Vojvodina, Serbia - short communication

Natural parasitism of the European corn borer eggs (Hübner) by Trichogramma spp. (Hymenoptera, Trichogrammatidae) was assessed in sweet corn field in north-west Serbia, region Vojvodina at the localities of Ruski Krstur, from 2004 till 2007. The rate of egg parasitism in 2004 varied from 35.89% to 73.58%. The parasitism in 2005 was lower than in 2004. On four different sampling dates in 2005 parasitism varied from 28.48% to 57.05% and averaged 39.4%. In 2006 parasitism fluctuated between 9.31 and 62.9%, averaging 32.15%. In 2007 parasitism varied from 36.8% to 54.54% and averaged 43.48%. The egg parasitoid species was identified as Trichogramma evanescens (Westwood). The study showed that this natural enemy occurred constantly in sweet corn fields but its number greatly fluctuated from year to year.

Impact of the Egg Parasitoid, Gryon pennsylvanicum (Hymenoptera: Scelionidae), on Sentinel and Wild Egg Masses of the Squash Bug (Hemiptera: Coreidae) in Maryland.

Seasonal changes in egg parasitism and predation rates on sentinel (laboratory-reared) and wild (naturally occurring) egg masses of the squash bug, Anasa tristis (De Geer), were evaluated in squash fields in Maryland from June through September in 2013 and 2014. Rates of egg parasitism were significantly higher on wild egg masses than on sentinel egg masses. Squash bug nymphal emergence was significantly higher on sentinel egg masses than on wild egg masses. Between the first week of July and the first week of September of both survey years, squash bug nymphs emerged from 24.2% of wild eggs compared with 46.2% of sentinel eggs and parasitoids emerged from 55.7% of wild eggs compared with only 21.8% of sentinel eggs. Sentinel egg masses significantly underestimated the rate of natural egg parasitism. The egg parasitoid, Gryon pennsylvanicum (Ashmead), was responsible for over 99% of parasitism of squash bug eggs. There was a significant negative correlation between parasitoid emergence and nymphal emergence, suggesting that parasitoids were able to suppress squash bug populations. The average rate of parasitoid emergence peaked on wild egg masses on the fifth week of July at 72.8%, whereas the average rate of nymphal emergence from wild egg masses was <20% from the fifth week of July until the first week of September. These results demonstrate that G. pennsylvanicum was able to efficiently track wild squash bug eggs throughout the season and that it has the potential to be an effective biological control agent of the squash bug in Maryland.