Location: Biological Control of Pests Research
2024 Annual Report
Objectives
1. Expand studies on discovery, culturing, production and evaluation of natural enemies for biological control and insects as animal feed.
1.a. Behavior and evaluation of black soldier fly as feed and fertilizer.
1.b. Characterization of traits for high efficiency of food conversion and development of Tenebrio molitor for mass production as animal feed.
2. Develop improved rearing methods and artificial diets to reduce costs of insect mass production.
2.a. Test of prey recognition and consumption rate of lady beetles reared on artificial diet or factitious food for multiple generations.
2.b. Determine the effect of diet on the nutritional value of Tenebrio molitor produced for animal feed.
Approach
The invertebrate predator Coleomegilla maculata De Geer (Coleoptera: Coccinellidae) will be used as a model invertebrate in this test. It is an omnivorous predator that has the capacity to utilize microalgae and synthetic pollen as food to obtain essential nutrients not present in unsuitable prey (Riddick and Wu, 2015). This colony has been in continuous culture without any addition of wild type individuals for more than 50 generations in a climate-controlled room (24°C, 50%–60% RH, 16 h photophase). Individuals originating from the colony and used in this experiment have been mass-reared for more than 10 consecutive generations on a proprietary mixture of freeze-dried, powdered brine shrimp eggs Artemia franciscana Kellogg, freshwater microalgae (Chlorella vulgaris Beijerink), and fatty acids, stearic acid (18:0) or myristic acid (14:0) (Riddick, unpublished data). Larvae and adults have no prior exposure to H. illucens. Yet, published work using larvae and adults from this colony, indicated that the eggs of the common housefly Musca domestica L. (Diptera: Muscidae) were suitable prey in experimental trials (Riddick et al. 2014). All life stages have been maintained in separate cages in the same climate-controlled room (24 °C, 50%–60% RH, 16 h photophase) for more than 10 years at the National Biological Control Laboratory (NBCL), USDA, ARS, in Stoneville, Mississippi.
Cultivated strawberry (Fragaria × ananessa Duch. cv. Chandler) will serve as model plants to test the effects of H. illucens larval frass, as a fertilizer, on plant health. Approximately 1,000 bare root individuals will be purchased from a commercial nursery in Redding, CA, as mentioned in previous research (Riddick et al. 2019). All individuals will be removed from cold storage in NBCL, then transplanted into “flats” over the course of several consecutive days. Excess dead roots will be trimmed away, using stainless steel scissors. Once in flats at a spacing of approximately 6 cm between individual plants, a light covering of peat soilless media will be applied over the roots; then watered using tap water. All plants will be setup on metal benches in a temperature-controlled greenhouse (20-22°C, natural lighting) in Stoneville, Mississippi, USA. One month later, the healthiest plants will be transferred to plastic (1.3 L) pots, one plant per pot, containing the same quantity of soilless media in each pot.
Progress Report
Five experiments were conducted in support of the “Mini-Stock Grand Challenge”, a multidisciplinary USDA-ARS project involving multiple scientists from different disciplines and different research units aimed to test the possibility of utilizing insects as animal feed. These experiments on the yellow mealworm were aimed to optimize the conditions for mass rearing and maximize biomass productivity. 1) Study of seasonal effects on early instar larval growth rate and the role of atmospheric pressure; multi seasonal observations have indicated that development time tends to be shorter during Fall and Winter. ARS researchers propose that events of high atmospheric pressure produced by cold fronts could be responsible. Correlating changes of atmospheric pressure with patterns of larval growth rate provided statistical models (polynomial linear models) that explain these effects on the mealworm’s development time. 2) The impact of the growth rate of young larvae on the final development time was determined, showing that larvae with higher growth rate at early stages of development complete development sooner and grow larger. 3) One of the most critical pieces of information that is lacking for the insect farming industry is the optimal temperature for mealworm productivity and growth. The optimal temperature for growth and reproduction of the yellow mealworm was determined in a two-stage experiment. The optimal range of temperatures was determined to be between 27 and 29°C, which is two degrees lower than what the industry is using currently. This will potentially increase productivity of insect farms while at the same time saving energy in the process 4) Another challenge of mealworm farming is the long time it takes to mealworms to complete development (between 6 to 9 months). New diets were designed to shorten development time. In laboratory evaluations, two formulations reduced development time by up to 4 weeks. These diets were mostly composed of agricultural by-products, which were identified in previous studies during 2023. The presence of rice bran in formulations improved mealworm responses increasing food conversion efficiency. 5) The effect of temperature on the food utilization efficiency of the yellow mealworm was tested. This study consisted of measuring larval growth and food consumption for a 13-week period in three different favorable temperatures (27, 29, and 31°C). This study is a continuation of the temperature effects described in #3 and results confirmed that temperatures below those used in current farm practices are detrimental to food conversion efficiency. The best results were observed at 27 and 29°C. Chemical analyses of the pupae to determine the effects of temperature on the mealworms nutritional composition are in progress. Two manuscripts are in preparation and two others are in the planning stage.
In collaboration with another project in the same unit, the potential of the house cricket and the yellow mealworm to eliminate the mycotoxin fumonisin was assessed. This study determined that both species were able to eliminate the mycotoxin in the frass without detectable levels of bioaccumulation in their bodies. New experiments to determine the potential of the house cricket to utilize and convert corn contaminated with mycotoxins were conducted. This study is still in progress and will conclude in September of this year. The objective of this study is to determine if the house crickets can consume mycotoxin contaminated corn and convert it into safe and useful biomass for animal feed. Food conversion efficiency, cricket mortality and levels of mycotoxin in cricket bodies and insect defecation (known as frass) will be measured at the end of this study. One publication and one manuscript has been submitted from this research.
The hypothesis that dried and powdered larvae of the black soldier fly (BSF) can be used as a cost-effective dietary supplement to mass rear lady beetles was tested in the laboratory. Replicated rearing bioassays were used with the pink spotted lady beetle as the test organism. Results revealed that BSF larval powder had slightly negative effects on lady beetle development but no negative effects on lady beetle reproduction when used as a supplement in diets. One published article and one poster presentation resulted from this work. Ongoing research is evaluating formulations of BSF that incorporate more BSF protein and less BSF fat in diets without harmful effects on lady beetle development or reproduction.
The hypothesis that black soldier fly (BSF) excrement (known as frass) can be used as an environmentally benign and readily available protein source in fertilizers for crop plants was tested in high tunnels. Potted strawberry plants were grown in replicated high tunnels with increasing proportions of BSF dry frass as fertilizer with or without combining a fish meal based commercial fertilizer. Results revealed that BSF frass can partially replace a fish meal-based fertilizer without significantly reducing strawberry plant growth, flowering, or fruit production. One publication and one poster presentation of the results of this experiment will be forthcoming. Ongoing research will seek to carefully refine the BSF based fertilizer formulation.
From previous research it was demonstrated that the development time of the yellow mealworm can be affected independently of temperature, relative humidity, and daily light cycle. A new study was completed demonstrating that a similar effect exists for larval growth rate at early stages. This study also tested the effect of the early stages growth rate differences on the larval development time and seasonal pupation blockage. Because larvae can’t reproduce, metamorphosis is essential to produce adults to maintain the colonies. The blockage of pupation is a phenomenon that has been observed in mealworm farms across the country and tend to occur mainly during summer. This study shows that increases in growth rate during early larval stages result in a reduction in development time, increase in pupal weight, and reduction in the incidence of pupal blockage. The seasonal effects on early instar growth rates fit a curvilinear model (polynomial cubic) and appear to be correlated with highs in atmospheric pressure. One manuscript is in preparation.
Accomplishments
1. Evidence for seasonal effects delaying and blocking pupation in the yellow mealworm. In the past 10 years, multiple inquiries from yellow mealworm producers have been received by ARS researchers at Stoneville, Mississippi, regarding a phenomenon observed in commercial colonies across the USA. Mealworms seem to fail to pupate and remain in larval stage until they die. This phenomenon has also been observed in experimental colonies in the National Biological Control Laboratory (NBCL). ARS researchers in Stoneville, Mississippi, have documented this phenomenon in colonies through 3 years of continuous observations. In conditions of controlled temperature, relative humidity and light scientists have demonstrated that development time is affected seasonally by environmental factors not controlled by the top-of-the-line laboratory equipment. Development time increases and decreases through the year peaking during summer and decreasing during winter even when mealworms are maintained at constant temperature, humidity, and deprived of light. This evidence is fundamental to identify that the phenomenon observed by producers is real and not an artifact of their rearing procedures. Attention have been diverted to solve the questions of what is causing this phenomenon and how to remediate it. Solving this problem will beneficiate commercial mealworm producers, insect farmers, and consumers of insect meal.
2. Mealworm diets that shorten development time. One of the disadvantages of the yellow mealworm as a farmed insect is the unusually long development time of its larval stage, requiring from 4 to 9 months to reach the pupal stage depending on rearing conditions and seasonal delay. An ARS researcher at Stoneville, Mississippi, have develop multiple diet formulations, composed of at least 80% of agricultural by-products, which can significantly shorten the larval development time of the yellow mealworm. These diets were the result of comprehensive nutritional studies based on self-selection methods. Evaluations reveal that some formulations shorten the development time by more than 30 days and can reduce or eliminate seasonal pupation blockage. These diet formulations could potentially solve the seasonal pupation blockage phenomenon experienced by commercial producers. These diets can be used by mealworm producers and farmers and could potentially reduce the production costs of mealworm biomass making it more competitive to other less sustainable sources of animal protein such as fish meal.
Review Publications
Morales Ramos, J.A., Tomberlin, J.K., Miranda, C., Rojas, M.G. 2024. Rearing methods of four insect species intended as feed, food, and food ingredients: a review. Journal of Economic Entomology. 19. Article toae040. https://doi.org/10.1093/jee/toae040.
Riddick, E.W., Walker, R.C., Rojas, M.G., Morales Ramos, J.A. 2023. Evaluation of black soldier fly Hermetia illucens as food for the pink-spotted lady beetle Coleomegilla maculata. Insects. 14(12):902. https://doi.org/10.3390/insects14120902.
Amorim, H., Ashworth, A.J., Arsi, K., Rojas, M.G., Morales Ramos, J.A., Donoghue, A.M., Robinson, K. 2024. Insect frass composition and potential use as an organic fertilizer in circular economies. Journal of Economic Entomology. Article toad234. https://doi.org/10.1093/jee/toad234.
Paulk, R.T., Abbas, H.K., Rojas, M.G., Morales Ramos, J.A., Busman, M., Little, N., Shier, T.W. 2024. Evaluating Acheta domesticus (Orthoptera: Gryllidae) for the reduction of fumonisin B1 levels in livestock feed. Journal of Economic Entomology. https://doi.org/10.1093/jee/toae025.
Robinson, K., Duffield, K.R., Ramirez, J.L., Cohnstaedt, L.W., Ashworth, A.J., Jesudhasan, P., Arsi, K., Morales Ramos, J.A., Rojas, M.G., Crippen, T.L., Shanmugasundaram, R., Vaughan, M.M., Webster, C.D., Sealey, W.M., Purswell, J.L., Oppert, B.S., Neven, L.G., Cook, K.L., Donoghue, A.M. 2024. MINIstock: Model for INsect Inclusion in sustainable agriculture: USDA-ARS's research approach to advancing insect meal development and inclusion in animal diets. Journal of Economic Entomology. 117(4):1199-1209. https://doi.org/10.1093/jee/toae130.