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United States Department of Agriculture

Agricultural Research Service

Research Project: SUSTAINABLE SYSTEMS FOR INTEGRATED PEST MANAGEMENT AND CONSERVATION AND ENHANCEMENT OF NATURAL ENEMIES
2009 Annual Report


1a.Objectives (from AD-416)
Develop vegetational designs and therapeutic interventions that foster desirable pest/natural enemy balances. Increase the foraging efficacy of parasitoids and other natural enemies of key pests of row crops. Develop spin-off benefits emerging from an understanding of natural systems, such as use of trained wasps for chemical biosensors in precision agriculture and food safety.


1b.Approach (from AD-416)
Research will focus on better landscape ecology practices for total habitat management, improved knowledge of inherent strengths in crop attributes, and development of biorational, therapeutic products/procedures which complement inherent strengths in the cropping systems and the development of decision-making tools that better utilize natural enemies in agronomic crops in the Southern Coastal Plain. Emphasis will be placed on development of control strategies for insect pests utilizing biological control, conservation tillage practices, cropping sequences, and cultural practices. Efforts will be directed toward conserving and enhancing natural enemies for managing primary pests of agronomic crops.


3.Progress Report
In 2009, several studies were conducted to understand spatiotemporal patterns of insect pests and their natural enemies and subsequently to test vegetational designs that enhance natural enemies.

We are continuing to conduct research on developing bio-based management strategies for control of stink bugs. We are continuing small plot studies to assess the economic feasibility of producing organic cotton and peanuts, but we have added organic corn into the crop rotation.

Stink bugs have increased in importance as pests of agricultural crops over the past several years, but there is very little information available on the abundance of stink bugs in corn. Therefore, the objectives of this 7-year on-farm study were to determine the species of stink bug pests feeding on corn, and the abundance of these pests and their natural enemies in corn fields in Georgia. The predominant stink bug pests were the southern green stink bug and the brown stink bug, and at least one generation of each of these pests occurred in corn each year. Generally, in later planted corn, some of the adults that developed on corn produced another generation of immature stink bugs in the crop. Stink bug adults were parasitized by fly parasites. Stink bug eggs were parasitized by tiny wasp parasites. Predators, such as the big-eyed bug, the pirate bug, spiders, and lady beetles, ate stink bugs on corn. In conclusion, corn does harbor populations of stink bug pests in Georgia, and so the role this crop plays in the distribution and abundance of stink bugs throughout the agricultural landscape needs to be ascertained to better understand how to manage stink bug populations.

Insect pollinators are essential for the reproduction of more than two-thirds of the world’s crop species, and beneficial insects play an important role in reducing or controlling populations of pest insects in agricultural farmscapes. These insects depend on nectar for their survival in these farmscapes. Because the flowers of milkweed provide a rich supply of nectar, establishing a habitat of tropical milkweed could possibly enhance beneficial insects and pollinators in south Georgia farmscapes. Therefore, the purpose of this study was to monitor feeding activity of these insects on tropical milkweed in a corn farmscape in south Georgia. Eight flowering potted plants of tropical milkweed were placed next to a corn field, and then insects feeding on nectar of these milkweed plants were observed and recorded throughout the day on weekly basis for the growing season in 2008. It was determined that many species of beneficial insects and insect pollinators fed on the nectar of topical milkweed, and for the first time scelionids and other small parasitoids were observed feeding on nectar of a milkweed species. Corn plants do not produce nectar, and so an addition of a habitat of nectar-producing milkweed plants in this environment could possibly enhance beneficial insects and insect pollinators.


4.Accomplishments
1. Crop specific predation and parasitism of stink bugs in agricultural farmscapes. Although there are several parasitoid species of eggs, nymphs and adults of stinkbugs, they currently do not sufficiently control populations of this major pest species. There is a need to find additional natural enemies of these species for biological control. We investigated Southern green stink bug egg mortality by placing sentinel egg masses in plots of soybean, Bt-cotton, Round up Ready (RR) cotton and peanut plants in the Southeast. Egg masses were photographed at placement and at 12h, 24h and 48h after placement to help evaluate relative predation and parasitism in the crops. After 72h, surviving egg masses were collected and held in the laboratory to assess parasitism. Predation of eggs was high in peanuts (74%) and soybeans (65%), and similarly lower in Bt (26%) and RR cotton (21%). Most egg predation in cotton and peanuts was attributable to fire ants. Parasitism was low overall but higher in the cotton (8%) than the peanuts (0.17%) and soybeans (2%). Both predation and parasitism were higher at plot edges than the centers of all three crops. These results suggest that there are crop specific predator species that are able to cause high mortality of stink bug eggs masses which allows us to further investigate their use as biological control agents in given agricultural landscapes in the region.

2. Chemical detection and learning in insects. Many insect species are able to detect chemical compounds at levels that are substantially lower than any technology currently available. We have recently determined that the learning ability of Microplitis croceipes is concentration dependent, and that a single wasp is able to learn and report two different concentrations of a compound using two specific behaviors. This ability is currently being exploited to determine their use in precision agriculture in areas such as detection of aflotoxin presence and concentration in peanuts as well as levels of infestation of herbivores and other diseases of crops in the region. Total time and cost will be substantially reduced at the peanut grading process as well as in the crop scouting process in the field.

3. Crop-to crop relay of arthropod species in continuous cropping systems. Crop production during the winter months on the coastal plain is typically defined by the production of small grains and a half-dozen winter legumes. In continuous cropping systems there is an intensive year-round rotation on the same site, and a minimal interruption of vegetative cover. In these systems arthropods can exploit sequential habitats and easily relay between host species. In the first year of this research we found that the density and diversity of beneficial insect species was substantially higher than pest species in blue lupin, Austrian pea and faba bean, and this trend carried over to the sequent sorghum crop. The proportion of pest species was highest in the fallow/weed treatments. These preliminary results indicate that the lupin, pea, and faba bean are desirable cover crops that can potentially increase the relay of beneficial insects into summer crops.

4. Host plant affinity of fall armyworm strains in wheat. The fall armyworm is a polyphagous crop pest with an unusually wide host range, and is represented by two strains in the southeastern U.S., including the “C-strain” with primary affinity for corn and sorghum and the “R-strain” with primary affinity for rice and turf. Presently, small grain crops are an integral part of southeastern agriculture, but have not yet been “typed” for their strain affinity. In winter wheat, fall armyworm infestations require that about 2% of the regional production receive insecticidal control. Unknown in this management process is the predominate strain that infests wheat and the potential of this strain to more aggressively infest subsequent summer grain crops such as corn or sorghum. The purpose of this research is to first determine the preference that each strain of fall armyworm has for wheat and other small grains grown in the region, and secondly determine the influence that these winter crops may have on insect damage in the following summer grain crops. Initial results indicate that wheat is capable of hosting both races of fall armyworm.

5. Composition and abundance of stink bugs in corn. Stink bugs have increased in importance as pests of agricultural crops over the past several years, but there is very little information available on the abundance of stink bugs in corn. Therefore, the objectives of this 7-year on-farm study were to determine the species of stink bug pests feeding on corn, and the abundance of these pests and their natural enemies in corn fields in Georgia. The predominant stink bug pests were the southern green stink bug and the brown stink bug, and at least one generation of each of these pests occurred in corn each year. Generally, in later planted corn, some of the adults that developed on corn produced another generation of immature stink bugs in the crop. Stink bug adults were parasitized by fly parasites. Stink bug eggs were parasitized by tiny wasp parasites. Predators, such as the big-eyed bug, the pirate bug, spiders, and lady beetles, ate stink bugs on corn. In conclusion, corn does harbor populations of stink bug pests in Georgia, and so the role this crop plays in the distribution and abundance of stink bugs throughout the agricultural landscape needs to be ascertained to better understand how to manage stink bug populations.

6. Natural enemies feeding on milkweed nectar. Insect pollinators are essential for the reproduction of more than two-thirds of the world’s crop species, and beneficial insects play an important role in reducing or controlling populations of pest insects in agricultural farmscapes. These insects depend on nectar for their survival in these farmscapes. Because the flowers of milkweed provide a rich supply of nectar, establishing a habitat of tropical milkweed could possibly enhance beneficial insects and pollinators in south Georgia farmscapes. Therefore, the purpose of this study was to monitor feeding activity of these insects on tropical milkweed in a corn farmscape in south Georgia. Eight flowering potted plants of tropical milkweed were placed next to a corn field, and then insects feeding on nectar of these milkweed plants were observed and recorded throughout the day on weekly basis for the growing season in 2008. It was determined that many species of beneficial insects and insect pollinators fed on the nectar of topical milkweed, and for the first time scelionids and other small parasitoids were observed feeding on nectar of a milkweed species. Corn plants do not produce nectar, and so an addition of a habitat of nectar-producing milkweed plants in this environment could possibly enhance beneficial insects and insect pollinators,


Review Publications
Olson, D.M., Cortesero, A.M., Rains, G.C., Potter,T., Lewis, W.J. 2009. Nitrogen and water affect direct and indirect plant systemic induced defense in cotton. Biological Control. 49:239-244.

Tillman, P.G. 2008. Laboratory effects of two organically-certified insecticides on Trichopoda pennipes (Diptera:Tachinidae). Journal of Entomological Science. 43(4): 408-417.

Tillman, P.G. 2008. Observations of stink bugs (Heteroptera: Pentatomidae) ovipositing and feeding on peanuts. Journal of Entomological Science. 43(4):447-452.

Scully, B.T., Nagata, R.T., Cherry, R.H., Trenholm, L.E., Unruh, J.B. 2009. Registration of 'Pristine' Zoysiagrass. Journal of Plant Registrations. 3(1):65-68.

Tillman, P.G., Lamb, M.C., Mullinix, Jr, B.G. 2009. Pest insects and natural enemies in transitional organic cotton in Georgia. Journal of Entomological Science. 44(1):11-23.

Tillman, P.G., Northfield, T.D., Mizell, R.F., Riddle, T.C. 2009. Spatiotemporal patterns and dispersal of stink bugs (Heteroptera: Pentatomidae) in peanut-cotton farmscapes. Environmental Entomology. 38(4):1038-1052.

Last Modified: 12/19/2014
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