2011 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), 2,721 first-year seedlings (from true seeds) and 795 established sweetpotato clones (second-year seedlings and advanced lines) were grown in field plots in 2010. Roots were harvested in October and November, 2010, 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 2010, over 25,000 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 2011. Studies on transmission of Sweet Potato Leaf Curl Virus (SPLCV) by the sweetpotato whitefly highlighted the increasing importance of this virus for sweetpotato growers. A collaborative study identified which crops and weed plants transmit SPLCV. Although the whitefly fed on all of the diverse crops examined and on most of the weeds examined, sweetpotato was the only crop that whiteflies transmitted this virus too. This is a potential problem because the virus can cause serious yield losses in sweetpotato. Other hosts for the virus were found to be several species of Ipomoea. This group of weeds consists of assorted types of morning glories which are related to sweetpotato. Knowing which wild and crop plants the whitefly transfers the virus to is important for the development of an effective management strategy for the disease and pest. Several cultural farm practices were evaluated and results indicate that whitefly populations and infection with some whitefly-transmitted viruses can be reduced. These cultural practices include mulching, intercropping, timing of planting, and crop rotation. Field releases of three predators (a lady beetle, a common green lacewing, and a mirid) were evaluated in cabbage, cucumber and squash for the management of the sweetpotato whitefly. Whitefly populations were reduced by about 25-45% using each predator. A study was completed on the impact on natural enemies when eight biorational insecticides are used to control whiteflies. Jojoba oil, Biovar and Neemix were the most compatible for the parasites and predators of whiteflies in three vegetable crops. Whiteflies are problems in both humid and dry environments. The impact of different levels of moisture in the air were evaluated on the performance of whitefly survival, egg laying, and body size. Low moisture had the most negative effect on the whiteflies.
Shapiro, M., El Salamouny, S., Shepard, B.M., Jackson, D.M. 2009. Plant Phenolics as Radiation Protectants For The Beet Armyworm (Lepidoptera: Noctuidae) Nucleopolyhedrovirus. Journal of Agricultural and Urban Entomology. 26:1-10.
Abd-Rabou, S., Simmons, A.M. 2010. Augmentation and Evaluation of a Parasitoid, Encarsia inaron, and a Predator, Clitostethus arcuatus, for Biological Control of the Pomegranate Whitefly, Siphoninus phillyreae. Archives of Phytopathology and Plant Protection. 43:1318-1334.
Simmons, A.M., Abd-Rabou, S. 2011. Inundative Field Releases and Evaluation of Three Predators for Bemisia tabasi (Hemiptera: Aleyrodidae) Management in Three Vegetable Crops. Insect Science. 18:195–202.
Jackson, D.M., Shepard, B.M., Shapiro, M., El Salamouny, S. 2009. Effects of Cucurbitacin on the Activity of Nucleopolyhedroviruses against Pickleworm Larvae. Journal of Agricultural and Urban Entomology. 26:95-106.
Jackson, D.M., Harrison Jr, H.F., Thies, J.A., Bohac, J., Mueller, J.D. 2011. ‘Liberty’ Dry-Fleshed Sweetpotato. HortScience. 46:125-129.