2009 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.
As part of the on-going sweetpotato breeding program at the U. S. Vegetable Laboratory (USVL), 191 first-year seedlings (from true seeds) and 435 established sweetpotato clones (second-year seedlings and advanced lines) were grown in field plots in 2008. Roots were harvested in October 2008 and evaluated for yield, quality factors (shape, color, texture, taste, etc.), and resistance to soil insect pests and nematodes. Most first- and second-year seedlings were discarded, while clones with desireable characteristics were retained in the program. In the fall of 2008, over 15,000 true sweetpotato seeds were collected from two polycross breeding nurseries of 25 parental lines each. One group of 625 seeds were challenged with root knot nematodes then evaluated for disease resistance and root characteristics (color and shape). Approximately 65% of the seedlings were discarded because they did not meet quality standards, and the remaining 154 seedlings were put into 5-plant field plots for further evaluation. Another group of 2,054 seedlings were transferred directly to the field in 2009 as single-plant plots. Also in 2009, 725 established sweetpotato clones were planted in replicated field plots at the USVL. Roots from these plots will be harvested in October. Three polycross nurseries were planted in 2009, with seed collection beginning in September. Over 11,000 seeds from the 2008 polycross nurseries were sent to cooperating plant breeders at Louisiana State University and North Carolina State University for field evaluation in 2009. In cooperation with a Research Agronomist, several sweetpotato genotypes were evaluated for susceptibility to damage from the herbicide, flumioxazin. There was a wide range of response to this herbicide among the genotypes. Research studies on the B-biotype sweetpotato whitefly (also call silverleaf whitefly) and on associated viruses which it vectors were conducted. Experiments were conducted which suggest that reflective mulch in conjunction with host plant resistance for watermelon can be useful in reducing attack by whiteflies while being friendly with natural enemies.
Reflective Mulch and Resistant Plants. The sweetpotato whitefly is a widespread insect pest. It damages vegetables and other plants when it feeds, and it also transmits many plant viruses to the crops. A reflective mulch (silver on black) along with some wild relatives of cultivated watermelon helped control the population of the sweetpotato whitefly. These results suggest reflective mulch in combination with host plant resistance may reduce attack by whiteflies.
5.Significant Activities that Support Special Target Populations
Participated in the White House Initiative on HBCUs- Technical Assistance Conference, Norfolk, VA, April 26-28, 2009. Served on a panel of representatives from different USDA agencies and presented a talk on “Land Grant Programs, USDA-ARS.”
Simmons, A.M., Harrison Jr, H.F., Ling, K. 2008. Forty-nine New Host Plant Species for Bemisia tabaci (Hemiptera: Aleyrodidae). Entomological Science (Japan). 11:385-390.
Jackson, D.M., Harrison Jr, H.F. 2008. Effects of A Killed-Cover Crop Mulching System on Sweetpotato Production, Soil Pests, and Insect Predators in South Carolina. Journal of Economic Entomology. 101:1871-1880.
Simmons, A.M., Abd-Rabou, S. 2009. Population of the Sweetpotato Whitefly in Response to Different Rates of Three Sulfur-Containing Fertilizers on Ten Vegetable Crops. International Journal of Vegetable Science. 15:57-70.
Mccutcheon, G.S., Simmons, A.M., Norsworthy, J.K. 2009. Effect of Wild Radish on Preimaginal Development of Diabrotica balteata and Agrotis ipsilon. Journal of Sustainable Agriculture. 33:119-127.
Simmons, A.M., Abd-Rabou, S. 2007. Survey of Natural Enemies of the Sweetpotato Whitefly (Hemiptera: Aleyrodidae) in Ten Vegetable Crops in Egypt. Journal of Agricultural and Urban Entomology. 24:137-145.