Augmentative Biological Control Agent Research Articles

Insight into the host-specificity of a native and a newly introduced parasitoid of Tuta absoluta and prospect for biological control

New strategies are urgently needed to control Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), one of the most destructive pests of tomato crops. Originating from South America, it is spreading rapidly and has evolved resistance to most common insecticides making it highly challenging to control. Regarding biological control, the parasitoid Necremnus tutae Ribes & Bernardo (Hymenoptera: Eulophidae) is widely present around the Mediterranean basin and has adapted to the invader playing a substantial role in its control. In addition, the neotropical parasitoid Dolichogenidea gelechiidivoris Marsh (Hymenoptera: Braconidae) has established accidentally following its host in Spain and Algeria and a classical biological control program using this species is ongoing in Sub-Saharan Africa. Understanding the trophic connections between D.gelechiidivoris, N.tutae, the targeted host T.absoluta and potential non-target hosts is essential to assess their value as augmentative or classical biological control agents and to promote their establishment in conservation biocontrol. We conducted host-specificity tests in the laboratory using four European leafminer species to evaluate the specificity of these two parasitoids to T.absoluta. We then assessed their affinity for T.absoluta by exposing sentinel plants with the alternative host Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) inside and around greenhouses and measuring each parasitoid species' field parasitism rate. Our results show that of the four non-target species tested in the laboratory, N.tutae attacked three, while D.gelechiidivoris attacked only P. operculella. In the greenhouse, N.tutae did not prefer P.operculella or T.absoluta, whereas D.gelechiidivoris preferred the latter. The mean parasitism rate of T.absoluta over the three-month monitoring period in the greenhouses reached 27% for N.tutae and 35% for D.gelechiidivoris. We discuss the importance of host affinity for understanding potential non-target effects and the value a natural enemy can have as biological control.

Aecial and Telial Host Specificity of Puccinia coronata var. coronata, a Eurasian Crown Rust Fungus of Two Highly Invasive Wetland Species in North America.

The Eurasian crown rust fungus Puccinia coronata var. coronata (Pcc) was recently reported in North America and is widespread across the Midwest and Northeast United States. Pcc is a close relative of major pathogens of oats, barley, and turfgrasses. It infects two highly invasive wetland plants, glossy buckthorn (Frangula alnus) and reed canarygrass (Phalaris arundinacea), and could be useful as an augmentative biological control agent. We conducted large greenhouse trials to assess the host specificity of Pcc and determine any threat to cultivated cereals, turfgrasses, or native North American species. A total of 1,830 accessions of cereal crop species and 783 accessions of 110 other gramineous species were evaluated. Young plants were first inoculated with a composite uredinial inoculum derived from aecia. Accessions showing sporulation were further tested with pure urediniospore isolates. Sixteen potential aecial hosts in the families Rhamnaceae and Elaeagnaceae were tested for susceptibility through inoculation with germinating teliospores. Thirteen grass species within five genera in the tribe Poeae (Apera, Calamagrostis, Lamarckia, Phalaris, and Puccinellia) and four species in Rhamnaceae (Frangula alnus, F. californica, F. caroliniana, and Rhamnus lanceolata) were found to be susceptible to Pcc, with some species native to North America. All assessed crop species and turfgrasses were resistant. Limited sporulation, however, was observed on some resistant species within Poeae and four other tribes: Brachypodieae, Bromeae, Meliceae, and Triticeae. Among these species are oats, barley, and Brachypodium distachyon, suggesting the possible use of Pcc in studies of nonhost resistance.

Hadronotus pennsylvanicus (Hymenoptera: Scelionidae): a biological control agent for pestiferous leaffooted bugs (Hemiptera: Coreidae)

Abstract In recent decades, the egg parasitoid Hadronotus pennsylvanicus (Ashmead) has gained substantial attention as an important natural enemy of pestiferous leaffooted bug species in the genera Anasa Amyot and Serville and Leptoglossus Guérin-Méneville. Throughout its native range of North America, H. pennsylvanicus parasitizes Anasa and Leptoglossus eggs in various vegetable and orchard systems. The overreliance on broad-spectrum insecticides in these systems and the demand for effective and sustainable coreid pest management strategies have motivated researchers to consider H. pennsylvanicus as an augmentative biological control agent. The potential use of H. pennsylvanicus as a classical biological control agent has also been studied in Europe in response to the rapid spread of Leptoglossus occidentalis Heidemann, an invasive pest causing significant economic losses to the European pine nut industry. Improved understanding of H. pennsylvanicus taxonomy, life history, host range, parasitoid–host ecology, laboratory rearing, and field deployment techniques have created a robust scaffold on which to build future biological control programs. This natural enemy profile reviews the current advances in the aforementioned areas of H. pennsylvanicus research and outlines the parasitoid’s prospects as a biological control agent.

Susceptibility to cold suggests low risk of establishment of a tropical parasitoid attacking the corn pest Sesamia nonagrioides

Low temperatures limit the distribution and performance of many crop pests and their natural enemies in non-native areas. Here we evaluated the lower thermal thresholds for survival, development and reproduction of the tropical species Cotesia typhae Fernandez-Triana (Hymenoptera: Braconidae), a gregarious larval parasitoid of Sesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae), an important corn pest in southern Europe. C. typhae is highly host specific and a very efficient biocontrol agent of S. nonagrioides in greenhouse, with minimal impact on non-target species. Immature and adult stages of the parasitoid were exposed to five constant temperatures ranging from 5 to 27 °C. High mortality was observed in all immature stages below 15 °C and thresholds for egg, larval, and external pupal development were between 10 and 15 °C. Adult locomotor activity decreased dramatically within this temperature range, and males were more susceptible to cold than females. Given these thermal limitations and based on winter temperatures recorded over the past 20 years, we estimated that C. typhae had a low probability to survive in French winters. This finding supports the safe use of C. typhae as an augmentative biological control agent against S. nonagrioides.

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.

Resident parasitoids associated with Drosophilidae in Michigan tart cherry orchards and woodland edges

Knowledge of the distribution and abundance of resident parasitoid species of Drosophila flies constitutes an important base for developing and implementing a biological control program for Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), an invasive pest that attacks ripening thin-skinned wild and cultivated berries and stone fruits. For this purpose, a field survey was conducted to identify the parasitoid community associated with D. suzukii infested sites in tart cherry orchards and woodlots in west, northwest, and central Michigan. Sentinel traps baited with D. suzukii larvae and pupae in banana slices were deployed in the center of tart cherry orchards, in woodlots adjacent to tart cherry orchards, and in woodlots isolated from any known commercial host of D. suzukii. Traps were placed from the beginning of July to the end of October 2021. Three parasitoid species that are known to use drosophilids as hosts were recovered from these traps. Pachycrepoideus vindemiae (Rondani) (Hymenoptera: Pteromalidae) and Leptopilina boulardi Barbotin, Carton &amp; Keiner-Pillault (Hymenoptera: Figitidae) emerged from the infested bananas. Leptopilina heterotoma (Thomson) was collected as an adult in a sentinel trap. Among these wasps, only P. vindemiae successfully parasitized D. suzukii pupae in the laboratory. This pupal parasitoid was abundant and widely distributed in both cherry orchards and woodlots. The highest number of P. vindemiae was collected from orchards, followed by woodlots adjacent to orchards, with woodlots without nearby cultivated fruit having the lowest detections. These findings suggest that future release of augmentative or classical biological control agents for D. suzukii could be successful in orchards post-harvest to control late-season populations of this pest.

Recent advances in the biological control of citrus nematodes: A review

Parasitic nematodes including Tylenchulus semipenetrans, Radopholus similis, Pratylenchus coffeae and Meloidogyne spp. are significant pests of citrus worldwide. Various microbes and soil-dwelling predatory mites (Acari: Mesostigmata) have been evaluated as augmentative biological control agents against citrus parasitic nematodes. Some microbial candidates have received attention as bionematicides with reduced environmental toxicity. They include fungi (Trichoderma spp., Purpureocillium lilacinum, Pochonia chlamydosporia, and mycorrhizae, Glomus spp.) and bacteria (Bacillus spp., Pseudomonas fluorescens, Streptomyces avermitilis, and Pasteuria spp.), that have been applied against nematodes parasitic in different citrus cultivars. To date, at least sixteen bionematicides based on fungi and bacteria have been developed and marketed for use in citrus crops in various countries. Integration of bionematicides with other management tools as well as the conservation and enhancement of indigenous antagonists, will further enhance the management of citrus parasitic nematodes. Promising research avenues are discussed.

Influence of competition and predation on survival of the hydrilla tip mining midge and its success as a potential augmentative biological control agent of hydrilla

Hydrilla verticillata is an aquatic weed that grows densely throughout the water column and is costly to manage. The hydrilla tip mining midge, Cricotopus lebetis, a potential augmentative biological control agent of hydrilla, feeds on the apical meristem preventing growth. The goal of this study was to quantify the influence of a predator (mosquitofish, Gambusia sp.) and a competitor (hydrilla leafcutter moth, Parapoynx diminutalis) and their interactions, on the ability of the midge to survive and feed on hydrilla. The first experiment involved six treatments established in 37.8 L tanks with combinations of the organisms, including larval C. lebetis. Survival to adult midge eclosion was significantly reduced in the presence of the predator but was unaffected by the competitor’s presence alone. Apical meristem damage was reduced when both the competitor and predator were present. The second experiment included four treatments with C. lebetis egg masses or larvae and the presence or absence of mosquitofish. Adding C. lebetis as eggs rather than as larvae increased midge survival in the absence of the predator. Midge survival was lower when larvae were added, but the predator had no additional effect. To facilitate successful establishment of the midge and control of hydrilla, high numbers of larvae should be released to overcome predation.

Cricotopus lebetis Intraspecific Competition and Damage to Hydrilla

Cricotopus lebetis Sublette (Diptera: Chironomidae) is an aquatic insect adventive in Florida. Evidence from previous studies suggest the insect may have value as an augmentative biological control agent for hydrilla, Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), but there are gaps in knowledge of the biology and life history traits. To increase understanding of this insect, this study was comprised of 3 experiments. In the first experiment, we investigated the productivity and survival rate of C. lebetis across 6 generations by analyzing our colony data. Then the effect of intraspecific competition on the rates of pupal and adult eclosion was studied by monitoring hydrilla tips in test tubes with varying numbers of larvae. Finally, the level of hydrilla stem tip damage caused by a C. lebetis larva was determined by monitoring tip damage following feeding of a known number of larvae on a standardized number of hydrilla tips. The first experiment revealed the average survival rate of C. lebetis from egg to adult was 16.4%. Approximately a third of the females (30.2%) oviposited. The egg masses had an average of 154.5 eggs per egg mass and an 83.7% fertility rate. Investigation of intraspecific competition revealed pupation and adult eclosion was highest with 1 C. lebetis larva per hydrilla stem tip. Evaluation of the impact of C. lebetis larvae feeding on hydrilla showed stem tips in treatments with C. lebetis larvae experienced 38% higher damage compared to stem tips in control treatments. Overall, this study provided valuable information useful in improving the mass rearing of C. lebetis and predicting the damage caused by C. lebetis. For example, for efficient mass rearing, an average of 1 larva per hydrilla tip should be maintained with the remainder of eggs being used for augmentative releases.

Trichogramma spp. as potential augmentative biocontrol agents of Poinciana looper, Pericyma cruegeri (Butler) (Lepidoptera: Noctuidae)

Poinciana looper, Pericyma cruegeri (Butler) (Lepidoptera: Noctuidae) is an endemic Australasian defoliator of iconic Poinciana (Delonix regia) trees. Poincianas, despite being exotic, are of significant urban value in subtropical and tropical Australia for their attractive form, flamboyant blooms and popular utility as shade and amenity trees. Poinciana looper larvae can cause extensive defoliation, reduced flowering, and become a nuisance to residents as caterpillars drop from trees, while in an urban setting, chemical control options are limited. The suitability of P. cruegeri eggs as a host for the commercially-available egg parasitoids Trichogramma carverae, Trichogramma pretiosum and Trichogramma nr. finiculatum was evaluated to determine their potential as augmentative biological control agents. One female of each of these Trichogramma species was exposed to ten P. cruegeri eggs and left for one hour to oviposit. The suitability of looper eggs as a host for each wasp species was measured by time for initial host acceptance, subsequent development time, emergence rates, egg mortality and sex ratios. All three Trichogramma species successfully utilised P. cruegeri eggs as hosts, causing an average 58 % reduction in P. cruegeri larval emergence. Female wasps generally accepted P. cruegeri eggs within one minute of introduction, and this did not differ between parasitoid species. Development time differed significantly between all three species, with T. pretiosum emerging after 14 days, and T. carverae requiring 18 days for development. Significantly more T. nr. finiculatum emerged compared with the other two species, partially due to multiple wasps emerging per host egg. P. cruegeri is a suitable host for all three Trichogramma species, but further research is required prior to embarking on a biocontrol program using these species.

Economic feasibility of an augmentative biological control industry in Niger

Farmers in Niger are vulnerable to high millet yield losses due to the millet head miner, Heliocheilus albipunctella De Joannis (Lepidoptera: Noctuidae), for which pest control options are limited. Researchers have developed a procedure to multiply and spread an augmentative biological control agent Habrobracon hebetor Say (Hymenoptera: Braconidae) which is effective in limiting millet yield losses due to the pest. This study assesses the economic viability of small businesses to produce and sell biological control agents. It analyzes the profitability of the businesses under alternative pricing regimes given estimated costs to produce and distribute biological control agents. The economic assessment provides budget analysis for potential businesses and discusses options for scaling, price setting, and organizing. Our study suggests that the small H. hebetor industry should turn a profit in Niger at relatively low prices for the biological control agents of $3.00-$4.00 per bag with 15 bags needed per village. Competitive wages are achievable for the businesses that sell to at least 13 villages. Each business would hire three workers from late May to late August. Commercialization of H. hebetor would generate opportunities for wide geographic distribution of the technology on a sustainable basis in Niger.

Graphosoma lineatum (Hemiptera: Pentatomidae): a suitable host for mass rearing Ooencyrtus telenomicida (Hymenoptera: Encyrtidae)

ABSTRACTThe species Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae) is currently being considered as a candidate for augmentative biological control agent (BCA) against several pests, including Halyomorpha halys (Stål) (Heteroptera: Pentatomidae). Protocols for mass production of a BCA need fundamental information on its biological attributes. Here we tested a possible laboratory host for the rearing of O. telenomicida: the common bug Graphosoma lineatum L. (Heteroptera: Pentatomidae). At tested conditions, O. telenomicida biological parameters were: rm 0.154, offspring production 84.07 specimens/female, sex ratio (% females) 71%, juvenile development time about 16 days, population doubling time 4.52 days, emergence rate about 90%.

A baseline study using Plantwise information to assess the contribution of extension services to the uptake of augmentative biological control in selected low- to lower- middle- income countries

The uptake of augmentative biological control agents (BCAs) is still limited, particularly in many low- to lower- middle- income countries. This study focuses on factors that affect the uptake of BCAs for arthropod pests by national extension partners (NEPs) in Plantwise—an agricultural development programme facilitating the establishment of plant clinics where farmers can obtain diagnosis and plant health advice. Using data generated by NEPs, BCA recommendations in extension material and given by extension workers in Ghana, Kenya, Zambia, India, Nepal and Pakistan were analysed. The rate of BCA recommendation ranged from 13.0 (Zambia) to 61.1% (India) in extension materials and from 0.0 (Zambia) to 18.2% (India) in recommendations given by extension workers. Knowledge, availability and price were identified as the main factors affecting the uptake of BCAs by NEPs. This baseline study gives novel insight into the potential of NEPs to facilitate the use of BCAs.

Effects of cold storage on the biological characteristics of Microplitis prodeniae (Hymenoptera: Braconidae).

The endoparasitoid Microplitis prodeniae Rao and Chandry is an important potential augmentative biological control agent for lepidopteran pests of vegetables and tobacco. However, cold storage of pupae is required to ensure that sufficient parasitoids are available when they are needed in the field. In this study, pupae were maintained at 0, 4 or 10°C for 5-50 days after which the adults were evaluated for emergence, pre-emergence period, sex ratio, female longevity, oviposition period, and fecundity. Cold storage did not affect the pre-emergence period or proportion of females; however, there was a significant reduction in emergence, female longevity, oviposition period, and fecundity with increased exposure to cold. The pre-emergence period was approximately 5 days, and approximately 50% of the emergent parasitoids were females. A cold storage regime of 10 days at 10°C had no effect on the parasitoids and adult emergence was greater than 50% even after 20 days at 10°C. There was no carryover of the cold treatment from parental to F1 and F2 generations. Thus, M. prodeniae can be stockpiled for field release by exposing the pupae to a cold regime and subsequently holding them for adult emergence at 28°C.

Isolation and DNA Barcode Characterization of a PermanentTelenomus(Hymenoptera: Platygastridae) Population in Florida That Targets Fall Armyworm (Lepidoptera: Noctuidae)

ABSTRACT Telenomus remus Nixon is a platygastrid egg parasite of the fall armyworm, Spodoptera frugiperda (J. E. Smith), with a history of use as an augmentative biological control agent in Central and South America. Efforts were made in 1975–1977 and again in 1988–1989 to introduce T. remus into the fall armyworm overwintering regions of southern Florida to mitigate infestations by this migratory pest, but in neither case was evidence of long-term establishment found. However, in 2009 and again in 2013, an unidentified Telenomus species was found attacking fall armyworm sentinel egg masses placed on corn plants or pasture grasses in the north-central Florida counties of Levy and Alachua. Taxonomic uncertainties have so far not allowed a conclusive identification of species by morphological keys. DNA barcode comparisons showed a single Florida haplotype in all collections that was identical to that found in a T. remus colony from Ecuador and very similar to a T. remus colony from Honduras. The T. remus ba...

Cold tolerance of the predatory ladybird Cryptolaemus montrouzieri

The effect of low temperature acclimation and diet on the supercooling point (SCP, the temperature at which the insect’s body fluids freeze) and lethal time (LTime, time required to kill 50 % of the population at a temperature of 5 °C) of the mealybug destroyer, Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae), was assessed in the laboratory. The SCP of acclimated adult ladybirds which were allowed to complete development to adulthood at 18 °C and a 8:16(L:D)h photoperiod, or at 25 °C and a 16:8(L:D)h photoperiod, and which were subsequently kept at 10 °C and a 12:12(L:D)h photoperiod for seven days, was −17.4 and −16.8 °C, respectively. These SCP-values were approximately 7 °C lower than the value of −9.9 °C for non-acclimated ladybirds maintained at a temperature of 25 °C and a photoperiod of 16:8(L:D)h throughout development and in the first week of their adult life. Also food source had a significant effect on the freezing temperature of C. montrouzieri: the SCP of ladybirds fed the citrus mealybug, Planococcus citri (Risso)(Hemiptera: Pseudococcidae), was 1.6 °C higher than the value of −17.2 °C observed for ladybirds provided with eggs of the flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). However, neither cold acclimation nor diet had a significant effect on the lethal times of C. montrouzieri. Overall, the time required to kill 50 % of the population at a temperature of 5 °C ranged from 12.8 days for ladybirds fed P. citri mealybugs to 14.4 days for ladybirds fed E. kuehniella eggs. All individuals exposed to a constant 5 °C had died by day 24. Based on the results from this laboratory study, it is deemed unlikely that C. montrouzieri could establish outdoors in western Europe, and it is therefore expected to pose little risk to non-target species in this area when used as an augmentative biological control agent.

The Diversity of Chironomidae Associated with Hydrilla in Florida, with Special Reference toCricotopus lebetis(Diptera: Chironomidae)

Hydrilla verticillata (L.f. Royle) (Hydrochari tales: Hydrocharitaceae) hereafter hydrilla is an aquatic plant that is widely distributed in the Old World. A dioecious form of hydrilla was in troduced into Florida in the 1950s, and has since spread across the southern USA (Schmitz et al. 1991; Langeland 1996). Hydrilla is a highly ag gressive weed which is known to displace native vegetation (Haller & Sutton 1975; Hofstra et al. 1999; Van et al. 1999), impede boat traffic and dis rupt water movement (Schmitz et al. 1991). In 1992, the chironomid Cricotopus lebetis Sublette (Diptera: Chironomidae) was discovered in Crystal River, Florida attacking the apical meristems of hydrilla, and may have potential as an augmentative biological control agent (Cuda et al. 2002, 2011). The origin of the midge is un known (Epier et al. 2000), and its distribution in Florida has not been determined. The midge dam ages hydrilla by mining in the apical meristem, which causes tip abscission (Cuda et al., 2002). The objectives of the current study were to exam ine the distribution and abundance of C. lebetis, and more generally of chironomid midges, associ ated with hydrilla in Florida. Six water bodies in Florida were surveyed to examine the distribution and abundance of chi ronomids associated with hydrilla; Lake Rowell (Bradford Co.) and Wacissa Springs (Jefferson Co.) in North Florida, Lake Tohopekaliga (Osecola Co.) and Bulldozer Canal (Brevard Co.) in central Florida and Lake Istokpoga (Highlands Co.) and Lake Okeechobee (Okeechobee Co.) in south-cen tral Florida. Each location was sampled quarterly from Jan, 2011 to Jun, 2012 for a total of 6 sam ples from all locations except Wacissa Springs, which was sampled 5 times. On each sampling oc casion, a 4-pronged steel hook attached to a rope was thrown into the water and dragged along the hydrosoil to collect hydrilla. Hydrilla plants were removed from the hook and placed in plastic bags (46 x 61 cm, -16 liter capacity) partially filled with water from the corresponding sample site. Sufficient hydrilla was collected on each sampling occasion to fill two bags approximately two-thirds full. A separate plastic container was filled with water from the corresponding site. Bags were placed in a cooler and transported to the labo ratory. Apical portions (5-8 cm) of 300 intact hy drilla tips were haphazardly selected from each sample and placed in open plastic containers (34 x 28 x 15 cm, L x W x H) in water collected from the corresponding site. Containers were placed individually in fine mesh emergence cages (50 x 50 x 50 cm) and aerated with an aquarium pump. Cages were monitored daily for 14 days for midge emergence. Adults were collected daily by aspira tor and placed in vials containing 95% ethanol. Specimens were initially sent to J. H. Epler for authoritative identification, but once a reference collection was assembled, most midges were lo cally identified. Species richness at each location was deter mined as the total number of midge species recov ered. Diversity was calculated using the Shannon Index, which combines aspects of species rich ness and evenness (how equally individuals are distributed among species) (Shannon 1948). The Shannon index measures the predictability that an individual selected in a sample will be a given species. Higher values of the Shannon index indi cate that individuals are more evenly distributed among species, whereas low values indicate that some species are much more common than others. The Shannon Index was calculated for each sampling location as follows:

Developmental Time and Survival of Trash-Carrying Versus Naked Green Lacewings, with Implications for Their Utility as Augmentative Biological Control Agents

Abstract Because of their importance and abundance as predators of pest insects in agroecosystems around the world, eight species of lacewings from four genera (Apertochrysa, Chrysopa, Chrysoperla, and Dichochrysa) were investigated to evaluate their performance when reared on eggs of Ephestia kuehniella Zeller, a factitious prey commonly used in mass rearing systems. In particular, a comparative assessment of trash-carrying versus naked species (ones not carrying trash on their backs) was performed. We measured the developmental times and survival rates of the eight green lacewings and compared these characteristics between trash-carrying and naked lacewing species. Survival during immature development was higher (77–87%) for the two naked species (Chrysopa pallens (Rambur) and Chrysoperla suzukii (Okamoto)) than for the trash-carrying species D. alcestes (33%). Immature and larval developmental times were significantly longer among the trash-carrying species than the naked species. The rapid development of naked green lacewings may be a strategy to decrease predation risk by aphid guarding ants and intra-guild predators.

Plantless rearing of the zoophytophagous bug Nesidiocoris tenuis

Nesidiocoris tenuis Reuter (Heteroptera: Miridae) is widely distributed in the Mediterranean area, where it is used as an augmentative biological control agent of several pests. This zoophytophagous predator maintains a close relationship with its host plants using them not only to feed on, but also as an oviposition substrate. In the present study, a plantless rearing system was developed and developmental and reproductive parameters of bugs that had no access to plant material were compared with their counterparts living on plants. Eggs deposited in an artificial substrate took longer to develop and had lower hatching rates than those laid in tomato leaves. However, the biological parameters of nymphs that had hatched from the artificial substrate did not differ from those of nymphs that had emerged from plants, suggesting that, besides water, no essential nutrients are absorbed from the oviposition substrate during embryogenesis. Our results regarding the role of plant feeding indicate that water acquisition is the critical function of phytophagy in N. tenuis. In addition, supplementary nutrients derived from plants had a positive effect on adult weight and significantly enhanced survival in the absence of prey. Plantless rearing for five generations led to a prolonged preoviposition period and lower egg hatching rates and adult weights, but other developmental and reproductive parameters were not adversely affected. Our experiments suggest that prolonged plantless rearing of N. tenuis is possible provided that the mirid has access to a nutritionally superior food like Ephestia kuehniella eggs.

Recurrent warming to improve cold storage of Trichogrammatids (Hymenoptera: Trichogrammatidae)

Cold storage can be used to slow development, facilitate accumulation of the organisms and accommodate fluctuating demand for augmentative biological control agents. Previous research suggested the possibility of improving cold storage of Trichogrammatids by recurrent warming, so we subjected Trichogramma ostriniae juveniles within Ephestia kuehniella host eggs to either 2°C constant or to 2°C with twice-weekly recurrent warming for 3 h to 20°C. Parasitoid subsamples were allowed to mature for 1–9 days before placement in cold storage for up to 8 weeks. Parasitism by parentals, progeny emergence and fecundity and longevity of progeny were measured weekly for 8 weeks. Relative to constant 2°C, recurrent warming generally improved emergence, fecundity and longevity, and all the response variables were affected by the interaction of temperature regimen, parasitoid maturity class, and cold storage duration. This implies the utility of recurrent warming to improve egg parasitoid performance and for extending the duration of cold storage.