Location: Biological Control of Pests Research
2019 Annual Report
Objectives
Objective 1: Discover new biological control agents for invasive insect pests, especially invasive hemipterans, such as the bagrada bug and the kudzu bug.
Objective 2: Develop practical, mass rearing methods for agriculturally important insects, especially insect pests needed for the production of their natural enemies (such as stink bugs), insect biological control agents (such as predatory pentatomids and coccinellids), and insects potentially important as a food supply for animals and humans (such as mealworms and crickets).
Sub-objective 2A: Develop a reliable method for continuous production of the green stink bug Nezara viridula.
Sub-objective 2B: Study new methods to produce extracts from the yellow mealworm Tenebrio molitor and the house cricket Acheta domesticus and incorporate them into artificial diets for the predators Podisus maculiventris and Coleomegilla maculata.
Sub-objective 2C: Evaluate agricultural by-products as sources of food for the production of Tenebrio molitor and Acheta domesticus.
Objective 3: Develop effective biological control strategies for insect pests of crops grown under cover (e.g. high tunnels and greenhouses).
Approach
Climate matching software will be used to determine the most likely locations of natural enemy adapted populations across native ranges of M. cribraria and B. hilaris. The USDA-ARS European Biological Control Laboratory near Montpellier, France, will play a key role regarding parasitoid introductions of B. hilaris from many regions of Asia and Africa. Scientists at the university in Japan will make additional collections across the geographic range of the host within Japan. Scientists at USDA-ARS-IIRU, Newark, DE, will provide his host specificity expertise and make his Asian contacts available for the Kudzu Bug project.
Development of artificial diets for N. viridula will be approached by detailed chemical analyses of plant foods suitable for development and reproduction of N. viridula approximating their nutritional requirements. Artificial diets will be formulated to replicate the concentration and ratios of major nutritional components of broccoli, green lima beans and raw peanuts, which have been used to rear N. viridula. Diets will be compared to natural food sources broccoli, green snow peas, and raw peanuts plus a nutrient supplement previously developed (unpublished). Rearing conditions other than diet, such as optimal rearing density and adult reproductive curves, will also be studied.
Extracts of T. molitor larvae and pupae and A. domesticus nymphs will be produced by freeze-drying them at -25ºC and by spray drying of homogenized insects. Dry samples will be ground to particles of at least 30 µm. Extracts produced from dried T. molitor pupae will be used to produce artificial diet formulations for C. maculata. The diet formulations will be compared on their suitability to produce quality predators using life table analysis of C. maculata. The formulations will also be compared to a control consisting of natural food. The same procedure will be used for artificial diet formulations for P. maculiventris.
Four different types of agricultural by products will be tested as viable options to formulate diets for T. molitor and A. domesticus. 1) Peanut shells, 2) corn cobs, 3) discarded cabbage, and 4) residual from corn fermentation for ethanol production. Each by-product will be chemically analyzed to determine the content of protein, lipid, and carbohydrate. Diets will be formulated by mixing ingredients with wheat bran at different ratios depending of their nutrient content based on the chemical analyses. Diets will be evaluated by determining and comparing immature survival, development time and the efficiency of food conversion for each of the two species of insects.
Release and evaluation techniques for lady beetles as predators of strawberry will be develop and evaluated. This study will involve (A) testing the effectiveness of augmentative releases of lady beetles to control aphids in high tunnels, (B) testing the predation potential of larvae in the presence of aphid-tending ants in the laboratory and in high tunnels, and (C) testing the assertion that molecules in wax filaments on the cuticle of S. creperus larvae subdue ant aggression.
Progress Report
The artificial diet formulation for the green stink bug was updated with new ingredients. Raw peanuts were substituted by roasted peanuts yielding a significant gain in immature survival. Vitamin C was increased in the new formulation increasing survival and fecundity after the full elimination of fresh vegetables. Preliminary evaluations showed that the green stink bug was able to complete development and reproduce in the new diet formulation in total absence of fresh vegetables. The new diet formulation was introduced to the main colony in late 2018, increasing survival and allowing significant reduction in space and labor. These results constitute a significant advance for the future of stink bug rearing.
Variants of the artificial diet formulation developed in past years for the pink spotted lady beetle using powders from different industrialized insect species were tested. Development rate, adult weight, and immature survival were compared among six diets using powders of the yellow mealworm (larva and pupa), the house cricket (spray-dried and oven-roasted), and house fly (larva and pupa). Diets were also compared with a control consisting of eggs from the flower moth (Ephestia kuehniella). Lady beetles grown on diets containing house fly powder developed faster, were larger, and had a higher immature survival than all other diets. Also, lady beetles reared on diets with house fly powder did not differ significantly from those reared-on moth eggs in development time, size, and immature survival. Future research will focus on comparing diets formulated using powders of commercially produced insects.
A study was planned to test the effectiveness of pink spotted lady beetles reared entirely on artificial diet for controlling spider mite infestations in greenhouse bean plants. This study was cancelled due to extreme reduction in the lady beetle colony which occured during the government shutdown. The colony was nearly lost but it was recovered after the shutdown ended. However, the size of the colony at June 20, 2019, still had not reached the necessary levels to do greenhouse releases during the summer and this study is not expected to be able to proceed this year.
Four cricket diet formulations formulated with agricultural by-products, which were developed last year, were evaluated and compared with commercial and reference diets. There was not a statistical difference in cricket biomass production between cricket colonies fed with the four new diets and the commercial diet formulation. However, the reference diet performed better than all diets tested. The reference diet was the only formulation containing dry beef liver and published studies have confirmed the value of beef liver enhancing cricket development, survival, and growth. Nutrient intake analysis showed that levels of vitamin B12 were the highest in the reference diet, while they were almost non-existent in the four new diets. Nevertheless, the performance of the new diet formulations was comparable to the commercial diet and their cost was much lower ($0.87, $0.64, $0.75, and $0.39 per Kg) than the reference formulation ($3.50 per Kg). Nutrient intake analysis followed by regression analysis of biomass production showed that the intake of vitamin C, sterols, and manganese had the most significant positive effect on biomass production. This information has significant relevance for future efforts to refine cricket diets.
Self-selection experiments were designed and executed to determine consumption ratios on seven different combinations of 17 by-products and two dry food products (potato and cabbage). Based on consumption ratios, it was determined that corn dry distiller’s grain (DDGS), canola meal, spent barley brewery grain, rice bran whole and defatted, and oat hulls were suitable for mealworm diets. This information has been used to develop seven new mealworm diets based on agricultural by-products. Nutrient intake analysis followed by regression analysis of biomass production showed that carbohydrate, fiber, polyunsaturated fat, vitamin E, and phytosterol had a significant positive impact on biomass production. The seven diets will be fully evaluated and compared with a control diet next year.
Because of loss of personnel, the maintenance of host plants and aphids to generate a sizable colony of the lady beetle, Scymnus creperus has not been possible and therefore, it has been impossible to conduct releases in high tunnels. However, a naturally occurring species Scymnus loewii has been observed consuming an adventive aphid (Aphis ruborum) on cultivated strawberry in high tunnels for two consecutive field seasons in Stoneville, Mississippi. Thus, natural predation of the aphid by a lady beetle is already occurring, but due to the small size of the naturally-occurring predator’s population, augmentative releases would still be necessary for effective control at high aphid densities.
At least one naturally occurring aphid parasitoid (Aphelinus varipes) has been attacking the same adventive aphid in high tunnels for two consecutive field seasons in Stoneville, Mississippi. This parasitoid has never been recorded to utilize this aphid species as host. Planned independent research will continue to estimate parasitism rates as well as parasitoid emergence rates under field (high tunnel) conditions, while team research will detect additional parasitoids (and perhaps hyperparasitoids) using DNA barcoding technology. This research suggests that the combination of predatory lady beetles and aphid parasitoids can be manipulated to curb populations of this adventive aphid on strawberry in high tunnels, making the spraying of aphicides unnecessary.
Accomplishments
1. Combined methods of dietary self-selection, nutrient matrix, and multiple regression analyses to develop oligidic insect diets. Insect diets that are formulated with no chemically defined ingredients such as grain flours, vegetables, and animal products are called oligidic. These type of diets are the least expensive to formulate and are the most stable and commercially viable. Because of their composition complexity, oligidic diets are the most difficult to develop requiring years of trial and error experiments followed by evaluations for insect performance. In previous work by ARS scientists at Stoneville, Mississippi, the use of self-selection techniques has been perfected to develop and optimize chemically define diets. Using analyses of nutrient composition and multiple regression has allowed the use of the self-selection technique to develop oligidic insect diets. This method works by using ingredient consumption data from multiple self-selection experiments with different combinations of ingredients. Consumption data of individual ingredients is used to calculate ingredient consumption ratios and nutrient intake ratios based on the known nutrient composition of the ingredients used in each experiment. Multiple regression analysis is used to correlate the intake of each nutrient with the biomass gain from start to finish of each experiment. This constitute a holistic approach for insect diet development that yields an instant estimate of the optimal nutrient intake ratios for insect growth and development. This new method is applicable to insects that are at least partially omnivorous and can consume food from diverse sources. Many insect predator species are omnivorous, such as lady beetles and stink bug predators. This new method of insect diet development has the potential to revolutionize insect diet development and can benefit all fields where insect mass rearing is required, including insect research, sterile male release efforts for eradication of invasive pests, biological control industry and research, and insects as food and feed industry.
2. DNA barcoding technology identified an adventive aphid and a new association with an aphid parasitoid on strawberry. Aphids can cause major economic damage to many crops such as small fruits, i.e., cultivated strawberry and blackberry throughout the world. One goal of organic agriculture is to minimize the use of pesticides. A key to managing aphids without pesticides is to first identify the species and any associated natural enemies. In team research by ARS scientists at Stoneville, Mississippi, morphology and DNA barcoding techniques identified an adventive species (Aphis ruborum) new to eastern USA. This species is widely distributed in Europe, North Africa, and central Asia. DNA barcoding also identified at least one parasitic wasp species (Aphelinus varipes), previously introduced into the USA for classical biological control of another aphid species (Russian wheat aphid). This research is significant because it reports a new state record for Mississippi, USA and the eastern-most establishment of the aphid in the USA. Also, the association of the aphid with the parasitic wasp has never been reported before, anywhere in the world, to our knowledge.
Review Publications
Fanatico, A.C., Arsi, K., Upadhyaya, I., Morales Ramos, J.A., Donoghue, D., Donoghue, A.M. 2018. Sustainable fish and invertebrate meals for methionine and protein feeds in organic poultry production. Journal of Applied Poultry Research. 27(4):437-448.
Riddick, E.W., Wu, Z., Eller, F.J., Berhow, M.A. 2019. Potential of 2,4-dihydroxybenzoic acid as an oviposition stimulant for mass-reared ladybird beetles. Journal of Insect Science. 19(2):1-6.
Cervantes, F.A., Backus, E.A., Godfrey, L., Wallis, C.M., Akbar, W., Clark, T., Rojas, M.G. 2017. Correlation of EPG waveforms from Lygus lineolaris feeding on cotton squares and chemical evidence of inducible tannins. Annals of the Entomological Society of America. 110:2068-2075.
Backus, E.A., Cervantes, F.A., Godfrey, L., Akbar, W., Clark, T., Rojas, M.G. 2017. Certain applied electrical signals during EPG cause negative effects on stylet probing behaviors by adult Lygus lineolaris (Hemiptera: Miridae). Journal of Insect Physiology. 105:64-75.
Mason, J.B., Black, R., Booth, S.L., Brentano, A., Broadbent, B., Connolly, P., Finley, J.W., Goldin, J., Griffin, T., Hagen, K., Lesnik, J., Lewis, G., Pan, Z., Morales Ramos, J.A., Ranalli, M., Rojas, M.G., Shockley, M., Stull, V., Swietlik, D.M. 2018. Fostering strategies to expand the consumption of edible insects: the value of a tripartite coalition between academia, industry, and government. Current Developments in Nutrition. https://doi.org/10.1038/s41598-017-10675-6.
Morales Ramos, J.A., Kelstrup, H.C., Rojas, M.G., Emery, V. 2019. Body mass increase induced by eight years of artificial selection in the yellow mealworm, Tenebrio molitor (Coleoptera: Tenebrionidae) and life history trade-offs. Journal of Insect Science. 19(2):1-9.
Riddick, E.W., Miller, G.L., Owen, C.L., Bauchan, G.R., Schmidt, J.M., Gariepy, T., Brown, R.L., Grodowitz, M.J. 2019. Discovery of Aphis ruborum (Hemiptera: Aphididae) and Aphelinus varipes (Hymenoptera: Aphelinidae) on cultivated strawberry in Mississippi, USA. Journal of Insect Science. 19(3):1-6. https://doi.org/10.1093/jisesa/iez045.
