Evaluation of Black Soldier Fly Hermetia illucens as Food for Pink-Spotted Lady Beetle Coleomegilla maculata.

The discovery of new and improved factitious and artificial diets is necessary for cost-effective rearing of predatory arthropods. This study evaluated Hermetia illucens black soldier fly (BSF) as a suitable alternative food source for rearing the predatory coccinellid Coleomegilla maculata (Cmac). The hypothesis that BSF larval powder was suitable food to support the growth, development, and reproduction of Cmac was tested in the laboratory. When compared to a standard in-house diet containing brine shrimp egg powder plus Chlorella vulgaris green algae and myristic acid (BSE+CM), the BSF and BSF+CM diets reduced immature growth and development. Immatures successfully reared to teneral adults were smaller when fed BSF or BSF+CM rather than BSE+CM. Combining BSF with a powdered artificial diet (AD), i.e., BSF+AD, did not improve predator growth or development, compared to Cmac reared on BSE+CM. Cmac oviposition responses, i.e., egg clutch production, to BSF vs. BSE+CM or BSF+AD vs. BSE+CM did not differ significantly. In conclusion, BSF has the potential to be food that supports Cmac oviposition behavior. Future research is necessary to discover an ideal mixture of BSF, BSE+CM, or AD that supports Cmac growth, development, and reproduction over multiple generations.

Differential Susceptibility of Coleomegilla maculata and Scymnus creperus Larvae to Aggression by Solenopsis invicta Workers.

The biological control of aphids by aphidophagous coccinellids is often hampered by aphid-tending ants or aggressive, invasive ants foraging for food. Aggressive species such as the imported fire ant Solenopsis invicta Buren may attack and kill coccinellid larvae. This study tested the hypothesis that wax-secreting Scymnus creperus Mulsant larvae are less susceptible than non-wax-secreting Coleomegilla maculata (DeGeer) larvae to S. invicta aggression. Laboratory experiments were set up using bird cherry-oat aphid Rhopalosiphum padi (L.) nymphs and adults (as prey for coccinellids) on barley leaves in arenas with either coccinellid species and with or without S. invicta workers. The presence of S. invicta reduced aphid predation by C. maculata but not Sc. creperus. The frequency of S. invicta attack was greater for C. maculata than Sc. creperus; mortality was significantly greater for C. maculata than Sc. creperus. The wax covering on Sc. creperus reduced S. invicta aggression. Unexpectedly, Sc. creperus larvae with the wax cover removed did not suffer more S. invicta attacks or increased mortality. In conclusion, the wax cover and, perhaps, the volatile or non-volatile compounds in the wax and on the integument of Sc. creperus larvae reduce S. invicta aggression. Further research could identify the wax compounds and determine their functionality as semiochemicals against S. invicta.

Evaluation of Artemia franciscana Cysts to Improve Diets for Mass Rearing Stethorus gilvifrons, a Predator of Tetranychus turkestani.

Stethorus gilvifrons is an acarophagous coccinellid distributed in the Mediterranean region and could potentially be mass-reared for the augmentative biological control of Tetranychus turkestani and related species on crop plants. The hypothesis that brine shrimp Artemia franciscana cysts can improve diets for rearing of S. gilvifrons was tested in laboratory experiments. The diet treatments included A. franciscana cysts (D1), A. franciscana cysts plus a vitamin B complex (D2), A. franciscana cysts plus date palm pollen (D3), and A. franciscana cysts plus date palm pollen and Ephestia kuehniella eggs (D4). The results indicated that D1 did not support immature development. D2 supported egg-larval development but not pupal-adult development. Both D3 and D4 supported development to the adult stage and reproduction. However, D4 was the most effective diet, determined by observations of S. gilvifrons oviposition behavior and fecundity. A life table analysis corroborated these results; an intrinsic rate of increase, net and gross reproductive rates, and mean generation time were best for S. gilvifrons fed D4 rather than D3. A mixed diet composed of A. franciscana cysts, date palm pollen, and E. kuehniella eggs can be used to mass rear S. gilvifrons.

Effects of Helicoverpa armigera Egg Age on Development, Reproduction, and Life Table Parameters of Trichogramma euproctidis.

The noctuid Helicoverpa armigera is an economically important pest of agricultural crops in Iran and other countries. Research is evaluating the capacity of Trichogramma parasitoids to control H. armigera populations on field crops. The objective of this research was to determine if young rather than old H. armigera eggs were optimal for Trichogramma euproctidis development, reproduction, and life table parameters. Bioassays involved exposing T. euproctidis mated females to H. armigera 14, 38, or 62 h old eggs within 24 h in laboratory arenas. Results indicated that the number of host eggs parasitized successfully by T. euproctidis decreased as host egg age increased. Host egg age had no significant effect on T. euproctidis adult emergence. Adults that developed in 14 h old eggs had greater longevity and fecundity than those that developed in 38 h or 62 h old eggs. The intrinsic rate of increase (r) was greatest, and the mean generation time (T) was lowest for T. euproctidis reared in 14 h old eggs. This study indicates that young H. armigera eggs are more suitable than old ones for T. euproctidis development and reproduction. This study is important because it provides evidence, for the first time, that T. euproctidis can utilize H. armigera as a rearing host. Using young rather than old host eggs could ensure the persistence of a T. euproctidis mass production system to support augmentative releases.

Volatile and Non-Volatile Organic Compounds Stimulate Oviposition by Aphidophagous Predators.

INTRODUCTION: Evidence that volatile organic compounds (VOCs) and non-VOCs stimulate oviposition by aphidophagous predators is scattered throughout the literature. The objectives of this review are to (1) compile records indicating that VOCs and non-VOCs are responsible for oviposition stimulation, (2) calculate an egg production ratio (EPR) for stimulated predators, and (3) determine if EPR is correlated with vapor pressure and molecular weight of active compounds. METHODS: The USDA (United States Department of Agriculture), National Agricultural Library, online digital catalog system was used to retrieve abstracts, then the full text of manuscripts on oviposition stimulants for predators. Oviposition-stimulating VOCs and non-VOCS were tabulated with molecular weights and vapor pressure estimates. EPRs were calculated for stimulated coccinellids, syrphids, and chrysopids. RESULTS: Both VOCs and non-VOCs stimulated oviposition behavior by coccinellids and syrphids, but not chrysopids. EPR was greatest for syrphids. Two VOCs, (E)-ß-farnesene and 3-methyl-2-butenal, stimulated very high EPR values by the syrphid Episyrphus balteatus. Regardless of predator taxa, EPR was negatively and positively correlated with molecular weight and vapor pressure, respectively. CONCLUSIONS: Syrphids (rather than coccinellids or chrysopids) produce more eggs in response to VOCs. Organic compounds with low-to-moderate molecular weights and moderate-to-high vapor pressures might be most effective oviposition stimulants for aphidophagous predators.

Effects of Three Artificial Diets on Life History Parameters of the Ladybird Beetle Stethorus gilvifrons, a Predator of Tetranychid Mites.

BACKGROUND: The ladybird beetle Stethorus gilvifrons (Mulsant) is an important natural enemy of tetranychid mites and functions as a biological control of these plant pests. The development, survival and reproduction of S. gilvifrons were studied when fed on three artificial diets. The components of the artificial diet that S. gilvifrons could be reared successfully on for one generation with no use of tetranychid mites were examined. METHODS: Artificial diets consisted of sucrose, honey, royal jelly, agar, yeast, date palm pollen supplemented in different diets with hen's egg yolk (AD1, as basic diet), Ephestia kuehniella Zeller eggs (AD2), or E. kuehniella eggs and 2,4-dihydroxybenzoic acid (AD3). RESULTS: Adults and larvae of Stethorusgilvifrons fed on AD1 had a shorter immature development and preoviposition periods than those fed on AD2 and AD3. The total number of deposited eggs was significantly higher for the females fed on AD3 than on the other diets. The intrinsic rate of increase (r) of S. gilvifrons was highest on AD3, followed by AD2, and AD1. CONCLUSION: Stethorus gilvifrons performed best on AD3, indicating the potential of this artificial diet for the mass rearing of this important predatory ladybird beetle.

Discovery of Aphis ruborum (Hemiptera: Aphididae) and Aphelinus varipes (Hymenoptera: Aphelinidae) on Cultivated Strawberry in Mississippi, USA.

An adventive aphid and novel host-parasitoid association from cultivated strawberry (Fragaria × ananessa Duch. cv. Chandler; Fragaria × ananessa Duch. cv. Camarosa) in Mississippi, USA are reported herein. The aphid, first detected in high tunnel cultivation, was found predominately on newly emerged, not fully developed leaflets of daughter plants in the Fall of 2016. By 2017, aphids and their associated mummies were observed on fully developed leaflets on mother plants of both cultivars. The aphid was identified as Aphis ruborum (Börner & Schilder) using morphology and DNA barcoding studies. In addition, DNA barcoding identified parasitoid adults emerging from aphid mummies as two cryptic species, Aphelinus varipes (Foerster) and Aphelinus albipodus Hayat and Fatima. Occurrence of A. ruborum in Mississippi represents a new state record and the eastern-most established record in the United States. The A. ruborum - A. varipes or A. albipodus host-parasitoid association is reported for the first time anywhere in the world.

Oviposition Strategies in Beneficial Insects.

AIMS AND SCOPE: The aim of this special collection is to highlight the importance of reproduction (ie, oviposition) in the life history, population dynamics, survival, and fitness of beneficial insects, broadly defined. Specific areas of interest include the (1) identification of natural products to boost oviposition; (2) importance of chemical cues in oviposition site selection; (3) influence of host plant defenses on oviposition success; (4) reproductive physiology and the frequency of egg laying; (5) trade-offs between maternal size and egg size; (6) foraging behavior, host selection, and oviposition in parasitoids; and (7) oviposition decisions in the face of intraguild predators.

Utilization of Quercetin as an Oviposition Stimulant by Lab-Cultured Coleomegillamaculata in the Presence of Conspecifics and a Tissue Substrate.

BACKGROUND: The discovery of natural products to improve the reproductive performance of mass-reared predators is an important aim for successful augmentative biological control. We tested the hypothesis that quercetin (a bioflavonoid) stimulates oviposition by the ladybird beetle Coleomegillamaculata in the presence of conspecifics and a tissue substrate. METHODS: We conducted bioassays in solitary cages (housing one female) and communal cages (housing 10 females) to estimate daily oviposition site preferences, egg production in response to quercetin in the presence or absence of a tissue paper substrate, and female “resting” positions. RESULTS: Females preferentially oviposited within 1⁻2 cm of quercetin powder, held in a tiny dish, at the base of cages. When given a choice, females oviposited in the dish with quercetin over a tissue paper substrate. In one of two experiments, they produced more egg clutches, regardless of oviposition site, when the quercetin and tissue were in close juxtaposition. Females “rested” on the tissue in the presence or absence of quercetin. CONCLUSION: This study provides evidence that quercetin can be utilized as an oviposition stimulant by C. maculata in a rearing system. Future research should determine if quercetin stimulates oviposition in other ladybird beetle species.

Do Bioflavonoids in Juniperus virginiana Heartwood Stimulate Oviposition in the Ladybird Coleomegilla maculata?

Maximizing the reproductive potential of ladybird beetles fed factitious foods or artificial diets, in lieu of natural prey, is a major challenge to cost-effective mass rearing for augmentative biological control. In this study, we tested the hypothesis that compounds in redcedar, Juniperus virginiana, stimulate oviposition in the ladybird Coleomegilla maculata. We also tested the prediction that several bioflavonoids, identified in heartwood fractions, elicited this behavioral response. Phenolic compounds were extracted from J. virginiana heartwood sawdust, separated into several fractions, then presented to adult beetles, in a powdered, pure form, in the laboratory. Females preferentially oviposited within 1 to 2 cm of fractions B, C, D, and E, but not A or the unfractionated extract, at the base of test cages. Chemical analysis identified bioflavonoids in heartwood fractions and subsequent bioassays using several identified in fractions C, D, and E confirmed that quercetin, taxifolin, and naringenin (to a lesser extent) stimulated oviposition. All tested fractions and bioflavonoids readily adhered to the chorion of freshly laid eggs but did not reduce egg hatch. This study demonstrates that several bioflavonoids stimulate oviposition by C. maculata and could be useful for mass rearing programs.

Identification of Conditions for Successful Aphid Control by Ladybirds in Greenhouses.

As part of my research on the mass production and augmentative release of ladybirds, I reviewed the primary research literature to test the prediction that ladybirds are effective aphid predators in greenhouses. Aphid population reduction exceeded 50% in most studies and ladybird release rates usually did not correlate with aphid reduction. The ratio of aphid reduction/release rate was slightly less for larvae than adults in some studies, suggesting that larvae were less effective (than adults) in suppressing aphids. Some adult releases were inside cages, thereby limiting adult dispersion from plants. Overall, the ratio of aphid reduction/release rate was greatest for ladybird adults of the normal strain (several species combined), but least for adults of a flightless Harmonia axyridis strain. The combined action of ladybirds and hymenopteran parasitoids could have a net positive effect on aphid population suppression and, consequently, on host (crop) plants. However, ladybird encounters with aphid-tending or foraging ants must be reduced. Deploying ladybirds to help manage aphids in greenhouses and similar protective structures is encouraged.

Does a Change from Whole to Powdered Food (Artemia franciscana eggs) Increase Oviposition in the Ladybird Coleomegilla maculata?

The limited availability of alternative foods to replace natural prey hinders cost-effective mass production of ladybird beetles for augmentative biological control. We compared the effects of powdered vs. whole Artemia franciscana (A. franciscana) (brine shrimp) eggs with or without a dietary supplement on development and reproduction of Coleomegilla maculata (C. maculata) (Coleoptera: Coccinellidae). We tested the hypotheses that (1) powdered A. franciscana eggs are more suitable than whole eggs; and (2) palmitic acid, a common fatty acid in natural prey, i.e., aphids, is an effective dietary supplement. Development time, pre-imaginal survival, sex ratio, and body weight of adults did not differ significantly amongst individuals fed powdered vs. whole eggs, with or without 5% palmitic acid. Significantly more oviposition occurred when females were fed powdered eggs than whole eggs and powdered eggs with 5% palmitic acid than whole eggs with or without 5% palmitic acid. A weak functional relationship was found between pre-oviposition time and total oviposition by females fed powdered eggs with 5% palmitic acid; pre-oviposition time decreased as oviposition increased. Food treatments had no significant differential effect on progeny (egg) hatch rate. In conclusion, a simple change in A. franciscana egg texture and particle size (i.e., blending whole eggs into a dust-like powder) increases oviposition in C. maculata. Supplementing powdered eggs with 5% palmitic acid might accelerate oogenesis (egg maturation) in some females.

Effects of Rearing Density on Survival, Growth, and Development of the Ladybird Coleomegilla maculata in Culture.

Our research focuses on developing techniques to rear ladybird beetles (Coleoptera: Coccinellidae). We evaluated the effects of rearing density on survival, growth, and development of Coleomegilla maculata. The hypothesis that a low to moderate rearing density has limited or no effects on survival and development was tested. C. maculata first instars were reared to pupae at a density of 1, 5, 10, 15, or 20 individuals per arena (2.5 cm high, 9.0 cm diameter, and 159 cm3 volume) and fed powdered brine shrimp (Artemia franciscana) eggs. More larvae survived at the 1 and 5 densities, but no differences were detected between the 10, 15, or 20 densities. Median survival rate was at least 90% for larvae and 100% for pupae at the 10, 15, and 20 densities. Development time, body weight, and sex ratio were unaffected by rearing density. Overall, this study suggests that C. maculata larvae can be reared successfully at a density of 20 larvae/159 cm3 (≈ 0.126 larvae/cm3) in containers provisioned with powdered A. franciscana eggs. Scaling-up the size of containers, and C. maculata density in these containers, should be possible.

Do plant trichomes cause more harm than good to predatory insects?

Plants use trichomes as a morphological defense against attacks from herbivores. The literature was reviewed to test the hypothesis that trichome-bearing (pubescent) plants do not cause more harm than good to predators. Forty seven records on interactions between plant trichomes and predatory insects were found. Overall, the records reveal that trichomes have more harmful than beneficial effects on predators. Fortunately, most harmful effects are sublethal; they usually affect movement, development, oviposition and predation potential. In worst cases, sticky exudates from glandular trichomes entrap predators. The hooked tips on non-glandular trichomes impale predators. Entrapped and impaled predators often die from desiccation or starvation. Plant cultivars with high (rather than low) trichome density cause the most harm, and trichomes on tomato and some beans often cause more harm than good to predatory beetles, true bugs and lacewings. Whether these harmful effects have a net negative effect on plant fitness is poorly known and ripe for study. When developing and testing cultivars with increased trichome-based resistance to herbivory, the question as to whether these technologies are compatible with the functional role of those predators (single or combined species) capable of suppressing herbivore populations should be considered.

Is Tetranychus urticae suitable prey for development and reproduction of naïve Coleomegilla maculata?

The lady beetle Coleomegilla maculata De Geer is an omnivorous predator that could help suppress aphid and spider mite populations on plants in greenhouses, plantscapes or interiorscapes. We are assessing the nutritional requirements and feeding behavior of C. maculata on target prey (spider mites) and factitious (unnatural) food. Our ultimate goal is to develop an efficacious diet to mass produce C. maculata. In this study, we tested the hypothesis that Tetranychus urticae Koch (two-spotted spider mite) is not suitable prey for development and reproduction of naïve C. maculata (i.e., with no prior exposure to T. urticae). Our objectives were to (i) provide baseline data on the effects of consuming T. urticae on C. maculata life history, (ii) to compare the effects of consuming all stages of T. urticae versus eggs of Musca domestica L. (common housefly), and (iii) to determine if the consumption of plant products was beneficial. We used C. maculata from a colony reared only on Ephestia kuehniella Zeller (Mediterranean flour moth) eggs. In experiments, C. maculata larvae were reared from the first instar to adult stage with prey/food in replicated arenas; adult females were paired with a single male with prey/food. The results showed that naïve C. maculata readily attacked and consumed T. urticae. Nevertheless, T. urticae was less suitable than M. domestica eggs for C. maculata development and reproduction. Applying a synthetic pollen-Chlorella alga powder (SPCA) in arenas containing T. urticae appeared to boost C. maculata female development and reproduction.

Identification of (-)-beta-caryophyllene as a gender-specific terpene produced by the multicolored Asian lady beetle.

This work reports the development and use of techniques for characterizing volatile chemicals emitted by the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), in an effort to identify the semiochemicals involved in establishment and persistence of overwintering beetle aggregations. Volatiles emitted from live beetles were detected by using whole-air sampling and solid-phase microextraction (SPME). Adsorbed volatiles were thermally desorbed and identified with gas chromatography-mass spectrometry (GC/MS). By comparing the chromatograms of volatiles emitted from live male and female beetles, a sesquiterpene, (-)-beta-caryophyllene, was found only in the females. The identity of (-)-beta-caryophyllene was confirmed by using NIST Library searches, comparing retention times with those of known standards, and by using higher-resolution GC/MS above bench top capability. Although SPME trapping detected a wider array of compounds compared to whole-air sampling, the latter method is better suited for automation. Unattended automated sampling is required for the continuous measurement of targeted compounds under dynamically changing incubation conditions. These conditions, mimicking natural overwintering conditions, are essential to our long-term goal of using this technology to detect and identify the aggregation pheromone of H. axyridis.