Dynamic Soybean Pest Management for Evolving Agricultural Technologies and Cropping Systems (From S-281)

NON-TECHNICAL SUMMARY: The soybean aphid is a new invasive insect pest of soybean in the United States. The damage potential of this new pest, and others that may be introduced, is currently unknown. The effects of transgenic soybean (Roundup Ready and Bt) and other developing cropping systems on arthropod populations needs to be assessed. This project examines the impact of the soybean aphid on soybean yield and quality, and addresses management practices than can help to reduce the losses caused by this and other insect pests.

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APPROACH: Replicated field plots, 8 rows x 15 m, will be used to investigate the impacts of transgenic soybeans on pest and beneficial arthropod populations. Insect densities and soybean phenology will be monitored weekly from soon after soybean emergence until crop maturity using regional project protocols (Obj. 1, 2, 3). Plots will be harvested with a plot combine and yield and quality comparisons made (Obj. 1, 2) and plots rated for virus infection (Obj. 3).
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PROGRESS: 2002/10 TO 2007/09 <BR>
Soybean insect pests cost Georgia producers over $4 million in costs of control and crop damage in 2007. Studies on the population dynamics of velvetbean caterpillars (VBC), stink bugs (SB), soybean loopers, threecornered alfalfa hoppers, and other arthropods on soybeans produced in a Roundup Ready system and a conventional system revealed little impact on the insect species observed. In particlar, economoic threshold levels of VBC, SBL, and SB were attained in both cropping systems in 2007. Research on the vegetable soybean system (edamame) in south Georgia has concluded that this commodity can be efficiently produced utilizing most of the soybean culture that is currently being recommended. However, stink bug damage was more prevalent than expected on edamame compared to conventional soybeans with similar stink bug densities, especially when planted in mid-June compared to mid-April or mid-May. Soybean aphids were observed on soybean a sixth year at the UGA Georgia Mountain Research & Education Center at Blairsville, GA. Aphids were observed in July-August in the two soybean varieties planted, and most were small summer dwarfts. Although aphid populations are low in northern Georgia, their presence is cause for concern about possible future pest outbreaks in the state's soybean crop. Tweleve soybean varieties and breeding lines were selected from the initial 68 orginal entries for advanced screening for stink bug and lepidopteran resistance. In the advanced study, stink bug damaged kernels ranged from 16.8 to 31.8% in 2007 under heavy stink bug population densities and defoliation ranged form 1.5 to 11.4% under light caterpillar populations. Studies have been initiated to examine the mechanisms for this resistance. In attempts to create green bean syndrome (plants remain green and don't senesce normally) soybeans depodded at R5 (pods filling with seeds) and R6 (pods contain full size seeds) remained green at harvest, and yielded only 680 and 215 kg/ha compared to 2526 kg/ha without depodding. Three insecticide trials were conducted in Georgia soybeans in 2007. Most products evaluated were effective on VBC. Chemical control of selected insecticides differed between SB species; however, Mustang Max insecticide was effective in controlling all four SB species examined. Yields were as much as 336 kg/ha higher in the insecticide treated plots compared to the control plots in 2007.
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IMPACT: 2002/10 TO 2007/09<BR>
Obtaining additional information on the impact of the herbicide tolerant soybean production system on arthropod communities will aid in refining the soybean IPM program as this technology advances. It appears that the vegetable soybean production system can provide an efficient alternative crop for producers looking for new ways to improve the profitability of their farming operation. Ag Economists are currently developing vegetable soybean crop budgets and exploring marketing options for Georgia producers. The soybean aphid is now established in north Georgia, and this pest will continue to be monitored for abundance and damage potential. Several soybean breeding lines have been identified with substantial resistance to stink bugs and/or velvetbean caterpillars. These lines will provide genetic material for future crosses and back crosses, hopefully resulting in the release of resistant varieties. It appears that pod injury (depodding) is at least partially the cause for soybean green bean syndrome, which can result in significant yield reductions in soybeans. Insecticide control recommendations will continue to be revised and updated annually to provide Georgia producers with the most effective and cost-efficient control options.