Location: Biological Control of Pests Research
2017 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to natural food sources broccoli, green snow peas, and raw peanuts plus a nutrient supplement previously developed (unpublished).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
Sub-objective 2A: A new diet formulation for the Southern green stink bug (Nezara viridula) was developed based on studies conducted the previous two years. The new formulation was preliminarily tested in a group of 500 newly hatched stink bugs. The new formulation allowed the stink bugs to complete development in a shorter period of time than the conventional food mix used in the stock colony. Adults resulting from this experiment were continuously fed with the formulation and they showed an egg production rate slightly higher than adults fed the conventional food mix. A full life table evaluation of the diet will be done the following year.
Sub-objective 2B: Mealworm pupae were dried by four different methods including, freeze dry, vacuum oven dry, air dry, and a combination of blanching at 95°C for 1 minute and then vacuum oven drying. Because mealworm pupae resist drying due to the presence of waxes in their cuticle, freeze drying was an inefficient method taking over 150 h to effectively dry the pupae. Vacuum oven and air drying were more effective because the higher temperatures (50°C) by-passed the wax protection of the cuticle, but natural enzymatic reaction of the insect blood occurred darkening their coloration and affecting their nutrient content. Blanching the pupae before drying prevented degradation by enzymatic reactions.
Sub-objective 2C: A total of 6 self-selection experiments of house crickets (Acheta domesticus) were conducted using different natural food products and agricultural by-products. Results of the relative consumption of each of the ingredients while presented in combination to crickets were used to develop 8 new cricket diet formulations. These diets will be evaluated for their efficiency promoting growth, development, and reducing mortality in cricket colonies in experiments planned by the following year.
Objective 3: Adults of the pink spotted lady beetle (Coleomegilla (C.) maculata) were released for aphid control on strawberry plants in 2 of 4 “old” high tunnels. Predatory mites (Phytoseiulus persimilis) were also released in 2 of 4 high tunnels for two-spotted spider mite control. Aphid and spider mite populations were reduced within two weeks of the releases. Aphid and spider mite densities are being continuously monitored in the high tunnels. As of last week, spider mite populations are beginning to build-up again and aphids are appearing on the daughter plants, which sprout from the end of runners (extending out of the pots). New release of C. maculata larvae are planned in several weeks to replicate the experiments conducted last year, using the daughter plants.
ARS National Biological Control Laboratory (NBCL) scientists at Stoneville, Mississippi, determined the female reproductive system morphology and developed a physiological age-grading system for the bagrada bug, Bagrada (B.) hilaris, female. Physiological age-grading can be used to assess reproductive health in not only mass-rearing colonies but also field populations as well.
Unique crystals were observed in both the midgut and oviducts of dissected bagrada bug, Bagrada hilaris by scientists at the ARS NBCL, Stoneville, Mississippi. In cooperation with Texas A&M University scientists, the crystals were identified, using X-ray diffraction techniques, as allantoin and DL-allantoin in combination with halite. While allantoin in a soluble form is often found in insect tissues and excreta; being present as a crystal, especially in such a large form, is unusual. More research is warranted to further understand mechanisms associated with such crystal formation in B. hilaris and can lead to a better understanding of the excretory process in this species and the role allantoin plays in the elimination of excess nitrogen.
Studies were completed by ARS NBCL scientists at Stoneville, Mississippi, to correlate adult age and female reproductive system development state of the Southern green stink bug, Nezara viridula. A preliminary age-grading system was developed which after completion can be used to assess reproductive health of both mass-rearing colonies and field populations.
Accomplishments
1. Implementation of density management new techniques into mealworm production system resulting in a 4-month reduction in development time and an increase of 1 fold in biomass production. Current mass production of Tenebrio (T.) molitor in commercial farms does not control adult and larvae density resulting in substantial inefficiencies in reproduction and biomass production, which make insect protein expensive. Previous studies conducted by ARS scientists at Stoneville, Mississippi, showed that adult density impacts fecundity and larval density impacts food utilization efficiency, development time, and survival. However, methods to determine densities of newly hatched larvae were lacking. ARS scientists at Stoneville, Mississippi, developed a new method to estimate young larval densities by correlating waste production with larvae numbers. Controlling larval densities in rearing trays increased production and reduced the space requirements for mealworm mass production by shortening the development time while increasing the growth rate of larvae. This new technology can result in substantial cost reductions of mealworm production and a subsequent price reduction of mealworms for animal feed and food ingredients for human consumption.
2. New discovery of allantoin crystals present inside the body of bagrada bugs. The bagrada bug, Bagrada hilaris is a polyphagous invasive herbivore pest in the United States and methods to control it effectively are lacking. ARS scientists at Stoneville, Mississippi, observed the presence of unique crystals in both, the midgut and oviducts of dissected bagrada bugs. Crystals were identified using X-ray diffraction techniques. Both acicular (i.e., needle-like, slender, and/or tapered) and cubic (i.e., cube shaped). Crystals of both types were detected in the midgut and lateral oviducts of females and midgut in males. The cubic crystals were identified as allantoin although the acicular crystals were most likely DL-allantoin in combination with halite. While allantoin in a soluble form is often found in insect tissues and excreta; being present as a crystal, especially in such a large form, is curious and raises some interesting questions. More research is warranted to further understand mechanisms associated with such crystal formation in bagrada bugs and can lead to a better understanding of the excretory process in this species and the role allantoin plays in the elimination of excess nitrogen, which may result in the development of novel methods of controlling this pest.
Review Publications
Rojas, M.G., Morales Ramos, J.A. 2017. A new report of Nezara viridula f. aurantiaca (Heteroptera: Pentatomidae) from a cultured population in Washington County, Mississippi. Journal of Insect Science. 17(1):1-3.
Riddick, E.W. 2017. Identification of conditions for successful aphid control by ladybirds in greenhouses. Insects. 8(38):1-17.
Morales Ramos, J.A., Rojas, M.G. 2017. Temperature-dependent biological and demographic parameters of Coleomegilla maculata (Coleoptera: Coccinellidae). Journal of Insect Science. 17(2):1-9.
Riddick, E.W. 2017. Spotlight on the positive effects of the ladybird Harmonia axyridis on agriculture. Biocontrol. 62(3):319-330.
Rojas, M.G., Grodowitz, M.J., Reibenspies, J., Reed, D.A., Perring, T.M., Allen, M.L. 2017. Allantoin crystal formation in Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae) females. Journal of Insect Science. 17(3):75:1-6.
Shapiro Ilan, D.I., Morales Ramos, J.A., Rojas, M.G. 2016. In vivo production of entomopathogenic nematodes. In: Microbial-Based Biopesticides – Methods and Protocols. New York, NY: Humana Press. 1477:137-158.
Shelby, K., Coudron, T.A., Morales Ramos, J.A. 2017. Uptake of dietary selenium by laboratory and field feeding Podisus maculiventris (Heteroptera: Pentatomidae). Florida Entomologist. 100(1):199-202. https://doi.org/10.1653/024.100.0134.
Sun, Y., Hao, Y., Riddick, E.W., Liu, T. 2017. Factitious prey and artificial diets for predatory lady beetles: current situation, obstacles, and approaches for improvement. Biocontrol Science and Technology. 27(5):601-619.
Haelwaters, D., Zhao, S.Y., Cottrell, T.E., Kesel, A., Fiedler, L., Herz, A., Hesketh, H., Hui, C., Kleespies, R.G., Losey, J.E., Murray, K.M., Nedved, O., Pfliegler, W.P., Raak-Van Den Berg, C.L., Riddick, E.W., Shapiro Ilan, D.I., Smyth, R.R., Steenberg, T., Van Wielink, P.S., Viglasova, S., Zhao, Z., Ceryngier, P., Roy, H.E. 2016. Parasites of Harmonia axyridis: current research and perspectives. Biocontrol. 62:355-371.
