Location: Insect Behavior and Biocontrol Research
2025 Annual Report
Objectives
1. Develop strategies for optimal use of biological control agents against invasive weeds such as air potato and Chinese tallow tree based on research that improves our understanding of factors that determine weed abundance, including biotic and abiotic elements and climatic region.
1.A. Determine the role of native natural enemies attacking a biological control agent (Caloptilia triadicae) in its introduced range.
1.B. Determine presence and importance of air potato leaf beetle chemical communication pathways to improve air potato biological control.
2. Develop and refine biologically-based control strategies for invasive insects such as the Argentine cactus moth, Harrisia cactus mealybug, and Old World bollworm, focusing on the use of parasitoids and disrupting pheromone cues.
2.A. Determine release factors that increase successful establishment of the parasitoid Apanteles opuntiarum against the Argentine cactus moth.
2.B. Determine the effectiveness of released control agents Anagyrus cachamai and/or A. lapachosus to control the Harrisia cactus mealybug (HCM) in Puerto Rico.
2.C. Determine the effectiveness of disrupting pheromone communication between gregarious cactus moth larvae as a sustainable management tactic for this pest in commercial cactus production areas.
2.D. Determine whether parasitoids that attack native Helicoverpa zea will also be successful against the potentially invasive Helicoverpa armigera.
3. Develop sustainable management strategies such as “push-pull” technology for controlling invasive whiteflies in vegetable production using naturally repellent plants, plant chemicals, trap plants, and green leaf volatiles together with natural enemy refuge plants.
3.A. Identify companion plants, products and chemical compounds that a) repel whiteflies and determine their efficacy in limiting pest dispersal into crops (“push” factors), as well as b) identify plants and products capable of attracting whiteflies into trap crops to facilitate control (“pull” factors).
3.B. Evaluate companion or refuge plants that “attract and reward” important whitefly predators.
3.C. Develop an integrated cropping system combining “push-pull” crops or plant products with natural enemy refuges for sustainable biologically-based control of whiteflies.
Approach
Invasive insect pests and weeds are among the most serious problems facing agricultural and natural ecosystems throughout the United States. This project plan describes research to improve implementation of biologically based tactics for non-pesticide management of insect pests and weeds through a better understanding of the pest species’ biology and interactions with host plants and natural enemies, as well as development of optimized approaches, technologies and strategies. One area of research will address improvement of techniques to enhance release success, establishment and impact of biological control insect species against invasive weed species such as the air potato and Chinese tallow tree. Another area of research focuses on the development of an integrated cropping system for control of whiteflies in vegetable crop systems using ‘push’ components consisting of naturally repellent plants or plant compounds, in conjunction with ‘pull’ components that consist of trap crops, complemented by refuge plants to attract and reward natural enemies. Finally, the use of host specific parasitoids for the protection of native cacti from the invasive Argentine cactus moth and the Harrisia cactus mealybug, and protection of crops from the potentially invasive Old World bollworm, will be studied. Therefore, the plan is expected to serve several stakeholders and customers, including researchers at land grant institutions, government and non-governmental organizations, growers, ranchers and commodity groups, and small-scale farmers and organic producers. The outcomes of this research project will improve the sustainability of agricultural production, reduce reliance on pesticides and reduce the environmental degradation caused by invasive pest species.
Progress Report
This is the final report for this project on objectives in National Program 304, Component 2, Weeds and Component 3, Insects and Mites. For Component 2, research was conducted on Problem Statements B, biological control and ecosystem research, and C, integrated approaches to weed management. For Component 3, progress related to Problem Statements A, early detection, prediction and monitoring of beneficial and pest arthropods, B, develop new or improved management tools and knowledge to control arthropod pests, and C, integrate management strategies to control arthropod pests. Substantial progress was made over the 5 years of the project. For Objective 1, progress was made towards the development of strategies for optimal use of biocontrol agents against weeds. Significant progress was made for Subobjective 1A in evaluation of the Chinese tallow tree defoliating moth, Caloptilia triadicae, against Chinese tallow resulting in determination that the moth was poorly suited in the Tallahassee, Florida, area for control due to minimal damage observed in the tallow tree plantation and poor overwintering survival under natural conditions. For Subobjective 1B, significant progress was made with the discovery that volatile chemicals released from damaged air potato plants attract air potato beetles and development of an attractive lure serves for both effective surveillance and management through targeting aggregation of beetles for air potato control. Also, strategies were developed and implemented by ARS researchers at Gainesville, Florida to improve success of release and establishment of the water hyacinth leafhopper for control of water hyacinth through incorporation of attractant factors that improve leafhopper retention and safe methods for transport and release of leafhoppers. Accomplishments from Objective 1 will result in improvement to both aquatic and terrestrial biocontrol programs and improve the implementation and outcomes of these programs for our stakeholders. Significant progress was made for Objective 2 and specifically for Objective 2C with the identification that female cactus moths avoid oviposition on cactus pads that are treated with extracts containing the larval trailing pheromone. Previous accomplishments identified that the trail pheromone will disrupt the larval life cycle. This new research now identifies that the application of the trail pheromone will have two modes of control for the cactus moth, ovipositional avoidance and life cycle disruption. Outcomes for Subobjectives 2A and 2B were significantly delayed due to issues with permitting of the biological control agents. Research for Subobjective 2D was limited due to difficulty in locating Old World bollworm, Helicoverpa armigera, in Puerto Rico and larval parasitoids of corn earworm, H. zea, and in Florida, progress was made investigating other parasitoids. Laboratory experiments demonstrated that the egg parasitoid, Telenomus remus, successfully attacks, develops in, and kills H. zea eggs and presumably would do so in closely related H. armigera eggs as well. Field sampling in Florida demonstrated that the cover crop crimson clover was an early season host plant for H. zea, however larval parasitism was low. These results suggest that egg parasitoids might be more effective in lowering H. zea, and presumably H. armigera, populations than larval parasitoids. For Objective 3, Subobjective 3A, significant progress was made through discovery that components of green leaf volatiles, the leaf acetates, were significantly attractive to sweetpotato whiteflies with lower attraction to green leaf alcohols. These green leaf volatiles are promising components for use in whitefly surveillance as well as a tool in controlling this major insect pest in vegetable crops. Subobjective 3B achieved significant progress towards understanding of plants and signaling compounds that attract important whitefly predators. Research was conducted utilizing maize with and without the presence of important defense genes. The research identified that the presence of these genes was critical for the attraction of omnivorous predators but were not as important to insectivorous predators. Attraction of predators to companion plants such as sweet alyssum, marigold, and African basil was demonstrated using leafy greens and strawberry crop host plants in high tunnel greenhouses. Blends of green leaf volatiles optimized for attraction of whiteflies were also attractive to the predatory bug Macrolophus praeclarus. However, this blend was not attractive to the beetle natural enemy Delphastus catalinae. The use of these green leaf volatile blends for monitoring and trapping whiteflies may also improve biological control of whiteflies in vegetable production. Progress for Subobjective 3C includes the application of the attractive leaf acetates from Subobjective 3A that leaf acetates as the “pull” tactic in a “push-pull” management system. Earlier results determined that three mustard varieties and garlic plants could serve as the “push” tactic. Progress was made in development and application of these components for larger-scale “push-pull” and flowering companion plants with components includes intercropping by planting different patterns and different ratios of repellent, trap, and companion plants.
Accomplishments
1. Better deployment to improve water hyacinth biocontrol. Water hyacinth is one of the most damaging aquatic weeds in the United States due to clogging of waterways, reduction of water quality and disruption of ecosystems. To control the plant and minimize negative environmental and economic impacts of traditional control measures, a biocontrol program using the hyacinth planthopper as a biocontrol agent for this weed has been developed. However, the implementation of control is challenging and limited due to the need to deliver undamaged but fragile leafhoppers to the field. ARS researchers in Gainesville, Florida, evaluated optimal methods to transport and deliver biocontrol agents to weed patches in the field. Both optimal transportation conditions and release protocols to maximize the retention of the agent to release sites were identified. This research is already being adopted by state departmental agencies to improve the implementation of their water hyacinth biocontrol program.
2. Chinese tallow flowering phenology model relating to biocontrol interactions with honey bees. Chinese tallow is a highly aggressive, invasive weed with toxic sap in the southeastern United States where it threatens wetlands grasslands and forests. Control efforts include potential use of biological control insects for targeted management. While the tree is considered an invasive weed, its flowers can provide important nutrition for honey bees. However, the seasonal timing of tallow flowering and the importance of its flowers as a nectar source compared to native plants is not well documented. Studies by ARS researchers in Gainesville, Florida, characterized the flowering phenology of tallow, and a review of the scientific literature was conducted to determine the historic use of tallow verses native plants for honey production. Tallow was found to have a maximum of a one-month blooming period. Additionally, existing native plants contribute significantly to honey production. This research has provided critical information to regulatory agencies evaluating the importance of interactions between Chinese tallow and honey bees regarding tallow control efforts.
3. Larval trail pheromone deters oviposition by cactus moth. The Argentine cactus moth, which threatens cactus farming and native cactus throughout the southern United States, continues to expand its range in North America. Historically, understanding chemical communication for moths has provided numerous venues for development of moth control strategies. ARS researchers in Gainesville, Florida, evaluated whether chemical cues affect oviposition by adult moths and discovered that female moths utilize chemical cues to guide selection of oviposition sites. The strong avoidance behavior of female cactus moths for cactus pads treated with extracts provided evidence of a larval trail pheromone. This research determined that the application of the trail pheromone results in ovipositional avoidance of treated cactus but also disrupts the behavior and success of the caterpillars. These research results will ultimately provide land managers with a single treatment that will have two modes of action to protect cactus from the cactus moth.
4. Egg parasitism of Helicoverpa zea. The native corn earworm, Helicoverpa zea and the invasive H. armigera are serious pests of cotton, soybean, vegetable, and horticultural crops. ARS researchers in Gainesville, Florida, confirmed in laboratory experiments that the egg parasitoid, Telenomus remus, attacks and develops in H. zea eggs and presumably in H. armigera eggs as well. Field sampling in Florida showed that the cover crop crimson clover was an early season host for H. zea, but larval parasitism was low resulting in less than 7% of the larvae collected to be parasitized. These results suggest that egg parasitoids might be more effective in lowering H. zea populations than larval parasitoids, and if H. armigera invades the United States, these natural enemies will be ready to attack H. armigera eggs.
5. Plant monterpene levels affect insect predators. Sweetpotato whitefly, Bemisia tabaci, is a major insect pest of vegetables, damaging crops through direct feeding, as well as vectoring many diseases that can devastate crops. Management is challenging, particularly for organic vegetable production and biological control strategies are the primary approach for control. ARS researchers in Gainesville, Florida, examined methods to enhance use of insects that are natural predators of the whiteflies through identification of attractive chemicals. Plants that produced different monoterpene volatiles were assayed for attractiveness to two whitefly predators, Macrolophus praeclarus and Podisus maculiventris. Results indicated that the odors were important for the attraction of M. praeclarus but were less important for P. maculiventris. By understanding interactions between plant odors, pests, and predators at the genetic level, plant breeders can improve these programs by selecting varieties with appropriate odors to optimize biocontrol strategies.
Review Publications
Griesheimer, J.L., Gaffke, A.M., Minteer, C., Mass, J.L., Hight, S., Martini, X. 2024. Response of Lilioceris cheni to herbivore induced plant volatiles from Dioscorea bulbifera. Arthropod-Plant Interactions. 19.Article 13. https://doi.org/10.1007/s11829-024-10123-z.
Gaffke, A.M., Li, D., Manrique, V., Abbate, A.P., Wheeler, G.S., Diaz, R. 2025. Tallow tree biological control and beekeeping: Assessing the misconceptions and possible resolutions to protect native ecosystems. Biological Control. https://doi.org/10.1016/j.biocontrol.2025.105720.
Gaffke, A.M., Miller, N.W., Sharma, A., Allan, S.A. 2024. Attraction of sweet potato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), and two generalist predators to green leaf volatile compounds. Insects. 15(10). Article 750. https://doi.org/10.3390/insects15100750.