Location: Biological Control of Pests Research
2018 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to natural food sources broccoli, green snow peas, and raw peanuts plus a nutrient supplement previously developed (unpublished).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
Efforts to refine artificial diets for the Southern green stink bug, Nezara viridula, have yielded new effective formulations that eliminate the need for fresh vegetables. New products recently introduced to the market, which include freeze-dried and air-dried vegetables have been incorporated in the new diets with successful results. Colonies of the stink bugs have been maintained for five generations using these diets in the absence of fresh vegetables. These diets could potentially be modified to rear other species of stink bugs providing new ways to study them for developing new methods of control. Full evaluation of these diets is under way using life table approach to compare the quality of the diet formulations with the natural food consisting of raw peanuts, sunflower seeds, and fresh vegetables.
Morphological changes in the reproductive system associated with reproductive age were characterized in the Bagrada bug, Bagrada hilaris, and the Southern green stink bug, Nezara viridula. This method could be useful in determining reproductive age of individuals from the field or from unknown age. Although this method is not required for determining reproductive age of cultured insects, it can be used to identify reproductive pathologies occurring in the colony. Necrotic processes observed in the ovaries of green stink bugs were linked to the presence of microsporidia parasites, which can be a problem in cultured colonies of stink bugs.
Previous research has established the effectiveness of using mealworm powder in artificial diets for the pink spotted lady beetle. New studies show that other insect powders are effective and even superior to the mealworm powders. Diets that incorporate house fly powder increased lady beetle survival and reduced development time as compared with diets incorporating mealworm powder. Lady beetles fed an artificial diet formulation incorporating housefly powder developed at the same rate as lady beetles fed a diet consisting of cereal moth eggs and shrimp eggs. Insect powders of several species are now commercially available providing a reliable source of ingredients for lady beetle diets. Experiments are under way to examine the potential of commercially available insect powders to provide economic ways to mass produce these predators.
A new method to develop insect diets based on self-selection of natural and by-products was used to develop four new diet formulations for the house cricket formulated with at least 80% agricultural by-products. A total of seven self-selection experiments were completed using different combinations of food ingredients. In all seven experiments, cricket relative consumption of the different ingredients converged in similar proportions of lipid, protein, and carbohydrate confirming the ability of the house cricket to self-select optimal nutrient combinations from diverse food sources. Stepwise regression analysis identified vitamins A, C, B1, B5, phosphorus, and sterols as the nutrients that impacted most significantly cricket biomass production. Comparison of four diet formulations developed using this method with a commercial cricket diet and a reference diet is under way. Preliminary results showed that diet 4 consisting of dry corn distilled grain, rice bran whole, rice bran defatted, canola meal, brewer’s yeast, dry cabbage, and alfalfa pellets produced more cricket biomass than the commercial and reference diets. Diets 1, 2, and 3 were all superior to the commercial diet. While the retail price of the commercial diet is $5.00 and the reference diet is estimated at $3.50 per Kg, the estimated cost of formulating diets 1, 2, 3, and 4 is $0.87, $0.64, $0.75, and $0.39 per Kg, respectively. These new diets hold great promises to reduce production costs of crickets while at the same time improving production of cricket biomass for animal feed and cricket powder.
A large colony of the lady beetle Scymnus creperus required for field releases in high tunnel greenhouses have not been possible due to difficulties in rearing its aphid prey. Another lady beetle, Stethorus (S.) punctillum, has been released as an alternative to curb populations of the carmine mite, Tetranychus (T.) cinnabarinus, on strawberry plants. Stethorus punctillum adults and progeny were effective in reducing the population of T. cinnabarinus by 95% within three weeks after release. The effectiveness of S. punctillum to control T. cinnabarinus populations on crop plants has not been previously reported and constitute a promising way to control this pest.
ARS scientists at Stoneville, Mississippi, in collaborative research with scientists from the University of Georgia, discovered an invasive aphid Aphis (A.) ruborum (Börner) and an aphid parasitoid Aphelinus varipes (Förster) on cultivated strawberry in high tunnel greenhouses in Washington County, Stoneville, Mississippi, USA. The occurrence of A. ruborum in Mississippi represents a new state record. The host-parasitoid association of Aphis ruborum and the parasitoid Aphelinus varipes has not been reported anywhere in the world. Based on our current research, natural enemies are capable of curbing A. ruborum populations on cultivated strawberry without any need for insecticide applications.
Accomplishments
1. Enhanced artificial diets for the pink spotted lady beetle. Commercial production of insect predators require the development of effective artificial diets in order to reduce production costs. In the past, artificial diets for insect predators have been ineffective producing quality predators due to nutrient deficiencies resulting from the lack of insect components in the diets. New artificial diets for the pink spotted lady beetle were developed by ARS scientists at Stoneville, Mississippi, using insect components derived from commercially available insect powders. Powders produced from yellow mealworm, house cricket, and house fly were incorporated to experimental artificial diet formulations and tested for their efficacy at producing quality lady beetles. Diets incorporating powders of the house fly produced lady beetles, which were of higher quality than the control diet and previously developed artificial diets containing mealworm powder. Also, insect powders derived from insects that were processed, such as oven roasted or blench and dry, were of higher quality than powders derived from row insects. These new diet formulations can be produced in high quantity at a reasonable price and constitute a promising solution to the costly mass production techniques currently used to produce lady beetles and other insect predators. If adopted by the biological control industry, these diet formulations could reduce the price of biological control agents. Reducing the cost of producing biological control agents could encourage the use of this method to control important pests and reduce the need for insecticide applications, which could benefit the environment and make agriculture more sustainable.
2. Agricultural by-products to develop diets for cricket and mealworm production as animal feed. Massive quantities of agricultural by-products are produced annually in the U.S. Most of these products, such as, distilled grains for ethanol production, rice bran, and extracted grain meals from vegetable oil production, are not fit for human consumption. However, some insects can feed on these products and convert them into useful animal protein. Insects produce high quality protein and could be an important alternative to fish meal in the formulation of feeds for different farm animals and aquaculture. The current costs of insect production at present are not competitive with fish meal due to inefficiencies of the rearing technology and high costs of insect diets. Using agricultural by-products to produce insect diets could reduce the cost of insect production. ARS scientists at Stoneville, Mississippi, developed diets for the house cricket and the yellow mealworm using 80-90% agricultural by-products. These diets produced insects of better quality than existing commercial diets at a much lower price. These diet formulations could allow the reduction of insect mass production by converting unusable agricultural by-products into valuable animal protein. The cost reduction of insect production could make it competitive with fish meal, which is an unsustainable source of animal protein required for the production of feeds for livestock and aquaculture. These new diets will benefit the existing insect production industry, which is one of the fastest growing industries in the U.S. Other industries, such as ethanol, vegetable oil, etc., will also benefit by the utilization of their by-products, which could become a commodity.
3. A novel method for developing insect artificial diets and feeds. Insect artificial diets have been considered a prerequisite for the economic mass production of beneficial insects as biological control agents. Current methods of insect diet development are complicated and ineffective due to the extreme complexity of the nutrient composition of the insect natural diets and nutritional requirements of insects. Detailed chemical analysis of insect’s natural diet have resulted in the development of chemically defined diets, which have been inferior as compared with their natural food. One of the problems is that in most of the cases the natural food of an insect species is not fully known and if known, the proportion in which each food item is consumed is unknown. ARS scientists in Stoneville, Mississippi, developed a new method of producing insect diet formulations based on self-selection of different ingredients or variations of formulations by insects followed by evaluation of insect biological parameters and statistical analysis to correlate nutrient ingested profiles to insect performance. This method uses information on insect consumption patterns of different ingredients and their resulting growth patterns to determine the impact of each nutrient on insect growth and development using multiple regression analysis. This new method will allow better control of the complexities of insect nutrition and facilitate the development of insect diets, at least for those species that are omnivore to some degree. 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.
4. Size increase in the yellow mealworm induced by selection. Although the production of insect protein holds promise as a substitute of fish meal in animal feed formulations, the market price of insect powders remain high due to the high costs of insect mass production under the current rearing systems. Current rearing procedures for insect mass production are primitive and have a great potential for improvement. Another aspect of insect biomass production that can be improved is the breeding of insect lines for more efficient growth and food conversion. ARS scientists at Stoneville, Mississippi, tested the possibility of obtaining improved lines of the yellow mealworm by selecting for a larger size. A continuous selection of larger mealworm pupae as reproductive stock for a period of 8 years has doubled the size of mealworm pupae in the experimental colony. This increase in size has not been accompanied by an increase in development time, which indicates that the growth rate of the mealworms has also increased. These results demonstrate the viability of selection strategy to improve the productivity of insect colonies and the potential that insect colonies have for further genetic improvement using conventional selection methods. Improved breeding stock could greatly increase the productivity and reduce costs of insect biomass production for animal feed.
Review Publications
Eisenberg, L., Johnson, S., Grodowitz, M.J. 2018. The reproductive morphology and physiological age grading of the female Salvinia Weevil, Cyrtobagous salviniae Calder and Sands. Journal of Insect Science. 10:1-8. https://doi:10.1177/1179543317751909.
Morales Ramos, J.A., Rojas, M.G., Dossey, A.T. 2018. Age-dependent food utilization of Acheta domesticus (Orthoptera: Gryllidae) in small groups at two temperatures. Journal of Insects as Food and Feed. 4(1):51-60. https://doi:10.3920/JIFF2017.0062.
Riddick, E.W., Wu, Z., Eller, F.J., Berhow, M.A. 2018. Do bioflavonoids in Juniperus virginiana heartwood stimulate oviposition in the ladybird Coleomegilla maculata? International Journal of Insect Science. 10:1-13. https://doi:10.1177/1179543318758409.
Ceryngier, P., Nedved, O., Grez, A.A., Riddick, E.W., Roy, H.E., San Martin, G., Steenberg, T., Vesely, P., Zaviezo, T., Zuniga-Reinoso, A., Haelewaters, D. 2018. Predators and parasitoids of the harlequin ladybird, Harmonia axyridis, in its native range and invaded areas. Biological Invasions. 20(4):1009-1031.
Portilla, M., Luttrell, R.G., Snodgrass, G.L., Zhu, Y., Riddick, E.W. 2017. Lethality of the entomogenous fungus Beauveria bassiana strain NI8 on Lygus lineolaris (Hemiptera: Miridae) and its possible impact on beneficial arthropods. Journal of Entomological Science. 52(4):352-369. https://doi.org/10.18474/JES17-15.1.
Riddick, E.W., Morales Ramos, J.A. 2017. In-transit temperature extremes could have negative effects on ladybird (Coleomegilla maculata) hatch rate. Trends in Entomology. 13:1-11.
Riddick, E.W., Wu, Z., Eller, F.J., Berhow, M.A. 2018. Utilization of quercetin as an oviposition stimulant by lab-cultured Coleomegilla maculata in the presence of conspecifics and a tissue substrate. Insects. 9:1-14.
Rojas, M.G., Elliott, R.B., Morales Ramos, J.A. 2018. Mortality of Solenopsis invicta workers (Hymenoptera: Formicidae) after indirect exposure to unformulated spores of three entomopathogenic fungi. Journal of Insect Science. 18(3):1-8.
