2010 Annual Report
1a.Objectives (from AD-416)
Specific objectives are to a) Identify and characterize host plant resistance to sweetpotato whitefly in melons and to the soil insect complex in sweetpotato, and facilitate incorporation of resistance factors into advanced breeding lines and new vegetable cultivars; b) assess the importance of biological control agents of sweetpotato whitefly and of insect pests of sweetpotato and cucurbits, and develop techniques for their conservation and utilization as management tools in vegetable production systems; and c) develop cost effective, biologically-based technologies for use in integrated pest management (IPM) programs for sweetpotato, cucurbits, and other vegetable crops.
1b.Approach (from AD-416)
Identify sources of resistance and determine heritability of resistance against sweetpotato whiteflies in melon and watermelon, and against soil insect pests of sweetpotatoes; facilitate incorporation of resistance into advanced sweetpotato breeding lines and new cultivars; determine chemical and physical mechanisms of resistance in sweetpotato to soil insect pests; investigate the influence of leguminous host plants on parasitoids of whiteflies; survey predators in South Carolina for biological control agents for whiteflies; determine overwintering ability of whitefly predator Delphastus catalinae; establish food preferences of predator Engytatus modestus; assess the use of baculoviruses for control of pickleworms, melonworms, and soil pests of sweetpotatoes; develop trapping methods for pickleworm moths, melonworm moths, sweetpotato weevils, Diabrotica spp., and whiteflies using pheromones and kairomones; evaluate alternative cropping systems for sweetpotatoes and other vegetables; and evaluate LED-modified traps for whitefly control.
A four-year study was completed on the use of combining host plant resistance and reflective mulch for the reduction of whiteflies in watermelon. The combination of these two management tools resulted in a reduced whitefly infestation, while two beneficial insects (a predator and parasite that attacks whiteflies) were not affected. Host plant resistance to aphids was observed in some wild watermelon plant types in collaborative research with Claflin University. In collaborative research with South Carolina State University, a study was conducted on the effect of humidity on the biology of whiteflies. Collaborative research between ARS researchers Charleston, SC and Beltsville, MD was continued on the predation of whiteflies based on predator gut analyses. A regional collaborative survey resulted in the discovery of a silk fly attacking sweet corn in SC and other states. The feeding stimulant Invite was evaluated to increase the efficacy of nucleopolyhedroviruses (NPV) against pickleworm larvae. This material significantly increased the efficacy of three NPVs against this pest of cucurbits. As part of the on-going sweetpotato breeding program at the U. S. Vegetable Laboratory (USVL), 2200 first-year seedlings (from true seeds) and 728 established sweetpotato clones (second-year seedlings and advanced lines) were grown in field plots in 2009. Roots were harvested in October 2009 and evaluated for yield, quality factors (shape, color, texture, taste, etc.), and resistance to soil insect pests and nematodes. Most first-year and many second-year seedlings were discarded, while clones with desirable characteristics were retained in the program. In the fall of 2009, over 30,000 true sweetpotato seeds were collected from two polycross breeding nurseries of 15 (dry-flesh) and 25 (moist, orange flesh) parental lines. Over 10,000 of these seeds were sent to cooperating plant breeders at Louisiana State University (LSU) and North Carolina State University (NCSU) for field evaluation in 2010. At the USVL in 2010, ca. 2700 first-year seedlings (from true seed) were transferred directly to the field in 2010 as single-plant plots, which will be harvested and analyzed in September, 2010. Also in 2010, 790 established sweetpotato clones were planted in replicated field plots at the USVL. Included in the 2010 field plots were cuttings of ca. 50 selected lines that had been evaluated in 2009 and returned from the LSU and NCSU evaluations. Roots from these plots will be harvested in October, 2010. Three polycross nurseries were planted in 2010, and seed collection will begin in September, 2010. Two groups of 12 and 30 sweetpotato clones were challenged with root knot nematodes and evaluated for disease resistance in a greenhouse experiment.
Jackson, D.M., Bohac, J., Thies, J.A., Harrison Jr, H.F. 2010. ‘Charleston Scarlet’ Sweetpotato. HortScience. 45:306-309.
Jackson, D.M., Lynn, D.E., Fuxa, J.R., Shepard, B.M., Shapiro, M. 2008. Efficacy of Entomophathogenic Viruses on Pickleworm Larvae. Journal of Agricultural and Urban Entomology. 25:81-97.
Simmons, A.M., Kousik, C.S., Levi, A. 2010. Combining Reflective Mulch and Host Plant Resistance for Sweetpotato Whitefly (Hemiptera: Aleyrodidae) Management in Watermelon. Crop Protection. 29:898-902.
Simmons, A.M., Ling, K., Harrison Jr, H.F., Jackson, D.M. 2009. Sweet Potato Leaf Curl Virus: Efficiency of Acquisition, Retention and Transmission by Bemisia tabaci (Hemiptera: Aleyrodidae). Crop Protection. 28:1007-1011.
Arno, J., Gabarra, R., Liu, T.-X., Simmons, A.M., Gerling, D. 2010. Natural Enemies of Bemisia tabaci: Predators and Parasitoids. pp. 385-421. In Bemisia: Bionomics and Management of a Global Pest, P.A. Stansly, S.E. Naranjo (eds.). Springer Dordrecht-Heidelberg-London-New York. pp. 385-421.