Progress 09/01/05 to 08/31/07
Outputs
A major constraint to the use of microbial (biological control) agents in managing insect pests in vegetable and other crops is their susceptibility to breakdown by sunlight (UV rays), thus making them ineffective. One part of this project's activities focused on finding natural, plant-derived materials (17), oils (11) and lignins (12) for their ability to act as sun screens. Of those tested, black tea and lignins were excellent sunscreens. Other outputs of the project include developing efficient field sampling techniques. Companion cropping a medicinal plant (feverfew) with other crops such as Echinacea was a useful technique for reducing numbers of whiteflies and thrips on Echinacea. Three cypoviruses isolated from cabbage looper, European peacock caterpillar, and Douglas fir tussock moth were propagated in cabbage looper and identified as Type 5 cypoviruses using dsRNA genome profiles in agarose gels. Field tests were conducted at Clemson to evaluate the
effectiveness of entomopathogenic nematodes and neem in reducing damage from pests in yellow squash and green beans. Combination treatments of neem plus nematodes reduced damage from pickleworm on squash. Damage from squash vine borer was also lower in nematode treated plots, but neem did not appear to enhance the activity of the nematodes. In bean plots, S. riobrave +neem significantly reduced damage by Mexican bean beetle. In laboratory tests with beet armyworm using the same six treatments, S. carpocapsae caused higher mortality than S. riobrave and neem was not effective against this pest. A non-pathogenic (binucleate) Rhizoctonia isolate and Bio-Yield Flowable (a mixture of beneficial bacteria) significantly increased the percentage of healthy broccoli plants and reduced the number of plants with wirestem 30 days after transplanting. To maximize biomass production, the cover crop Cahaba White vetch should be seeded in October or November and incorporated in January or February in
coastal South Carolina. Cahaba White vetch reduced the number of wilted seedless watermelon plants in one of two experiments compared with no control. Vetch was less effective than soil fumigation with Telone C-35. The plant defense activator Actigard increased the number and weight of seedless watermelons, even though it had no effect on percentage of wilted plants. The alternative pesticide ProPhyt, a phosphoric acid material, reduced severity of downy mildew on collard, reduced weight of diseased leaves, and increased weight of healthy leaves. It was the only product of 11 tested that differed from the non-treated control for all three measurements. The biofungicide Sonata was not effective when applied alone, but was effective when combined with a half rate of ProPhyt. Four cucurbit rootstocks used to produce grafted seedless watermelon were resistant to the watermelon pathogen that causes Fusarium wilt. Three resistant rootstocks were Lagenaria and one was an inter-specific
hybrid of Cucurbita species. However, these rootstocks are not immune to infection. Isolates of Fusarium pathogenic to watermelon were obtained from watermelon grafted onto rootstocks and planted in infested soil in the field.
Impacts
Vegetable consumption has increased by 15% per year for the past several years. Vegetable crops receive the highest pesticide load of any crop with over 240 million pounds used annually at a cost of over $480 million in the Southeastern U.S. alone. Alternatives to chemical pest control, identified by this project, will significantly reduce dependence on chemicals. Development of cypoviruses as microbial control agents has been hindered by lack of basic information on these viruses. Sequence information obtained in these studies will provide information on host specificity, identification of virus isolates, and detection of these viruses in the field. Most home gardeners prefer not to use chemical pesticides for squash vine borer so a safe alternative is badly needed. We have shown that entomopathogenic nematodes can reduce damage from this pest and allow plants to survive and produce squash late into the summer. We have also shown that the plant-derived compound, neem
can enhance nematode activity against certain pests and may suppress certain fungal pathogens that affect vegetable crops. The use of plant-derived materials to extend the life of microbial agents in the field will allow safer food production without harmful chemical pesticide residues that harm non-target organisms and contaminate water supplies. Natural sunscreens that extend the life of insect microbial (biological control) agents in the field are safe, natural and cost effective in commercial vegetable production and in home gardens. In leafy greens (particularly collards) in South Carolina, applications of chemical insecticides have decreased from 14 per season to 4 or 5 microbial control agents targeted mainly for the diamondback moth. Because of training provided, more vegetable producers, including limited resource producers, have improved knowledge of pest and natural enemy identification, scouting procedures, and use of bio-rational pesticides. All reported that with this
increase in knowledge the number of chemical sprays was reduced. In addition, they shared this information with their peers. Most farmers indicated that through the use of the new integrated pest management training, money was saved; the limited resource growers stated amount unknown but the larger commercial growers indicated approximately $180/acre was saved. Companion planting with the medicinal plant feverfew builds populations of natural enemies (predators and parasitoids) and may have applications in vegetable crops. This approach has already been shown to reduce insect pest populations in Echinicea when companion cropped with feverfew. Two biocontrol products reduced wirestem on broccoli as well as a soil-applied fungicide. They can be applied to transplants in the greenhouse, which reduces labor costs of field applications to a larger area. Optimum seeding and harvest dates were found for hybrid common vetch, a legume winter cover crop that is resistant to Southern root-knot
nematode. ProPhyt is an excellent alternative to conventional synthetic fungicides to suppress downy mildew on collard.
Publications
- Canhilal, R., G. R.Carner, and R. P. Griffin. 2006. Life history of the squash vine borer, Mellitia cucurbitae (Harris) (Lepidoptera: Sessiidae) in South Carolina. J. Agric. Urban Entomol. 23: 1-16. Canhilal, R. and G. R.Carner. 2006. Efficacy of entomopathogenic nematodes (Rhabditidae: Steinernematidae and Heterorhabditidae) against the squash vine borer, Mellitia cucurbitae (Lepidoptera: Sessiidae) in South Carolina. J. Agric. Urban Entomol. 23: 27-39.
- Canhilal, R. and G. R. Carner. 2006. Natural occurrence of entomopathogenic nematodes (Rhabditidae: Steinernematidae and Heterorhabditidae) in South Carolina. J. Agric. Urban Entomol. 23: 159-166.
- Farrar, R. R., M. Shapiro and M. Shepard. 2007. Relative activity of baculoviruses of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). BioControl. 52:657-667.
- Jackson, D. M., R. Canhilal, and G. R. Carner. 2005. Trap monitoring squash vine borers in cucurbits. J. Agric. Urban Entomol. 22: 27-39.
- Keinath, A. P., K. L. Everts, D. B., Langston, Jr., D. S. Egel, D. S., and G. J. Holmes, 2007. Multi-state evaluation of reduced-risk fungicides and Melcast against Alternaria leaf blight and gummy stem blight on muskmelon. Crop Protection 26: 1251-1258.
- Keinath, A. P., V.B. DuBose, W.H.May III, and W.P. Wechter. 2007. Evaluation of biopesticides to manage bacterial leaf spots on turnip greens. Plant Disease Management Reports 1:V104. Keinath, A. P., V.B. DuBose, W. H.May III, and W. P. Wechter. 2007. Evaluation of Actigard and Kocide to manage bacterial leaf spots on turnip greens. Plant Disease Management Reports 1:V103.
- Keinath, A. P. 2007. Sensitivity to azoxystrobin in Didymella bryoniae isolates collected before and after first use of Quadris fungicide in South Carolina. Phytopathology 97:S55.
- Khan, M.F.R., R. P.Griffin, G. R.Carner, and C. S.Gorsuch. 2005. Susceptibility of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), from collard fields in South Carolina to Bacillus thuringiensis. J. Agric. Urban Entomol. 22: 19-26.
- Lopez, R. and B. M. Shepard. 2007. Arthropods associated with medicinal plants in coastal South Carolina. Insect Science. 14: 353-358.
- Lopez, R. and B. M. Shepard. 2007. Feverfew as a companion crop reduces spider mites, whiteflies and thrips in other medicinal plants.33,37. In: Proceedings of the International Symposium: Medicinal and Nutraceutical Plants, A.K. Yadav (Ed). Macon, GA, USA.
- Shapiro, M., B. M. Shepard and R. Lopez. 2007. Effect of spices upon the activity of the gypsy moth (Lepidoptera: Lymantriidae) nucleopolyhedrovirus. Journal of Entomological Science.
- Njoroge, S. M. C., M. B. Riley, and A. P. Keinath, 2008. Effect of incorporation of Brassica spp. residues on population densities of soilborne microorganisms and on damping-off and Fusarium wilt of watermelon. Plant Disease 92: 287-294.
- Wechter, W. P., M. W. Farnham, J. P. Smith, and A. P. Keinath, A. P. 2007. Identification of resistance to bacterial leaf spot among Brassica juncea and Brassica rapa Plant Introductions. HortScience 42:1140,1143.
- Keinath, A. P. 2007. Sensitivity of populations of Phytophthora capsici from South Carolina to mefenoxam, dimethomorph, zoxamide, and cymoxanil. Plant Disease 91:743-748.
- Keinath, A. P., G. J. Holmes, K. L. Everts, D. S. Egel, and D. B. Langston, Jr., 2007. Evaluation of combinations of chlorothalonil with azoxystrobin, harpin, and disease forecasting for control of downy mildew and gummy stem blight on melon. Crop Protection 26:83-88.
|
Progress 09/01/05 to 09/01/06
Outputs
Bt transgenic sweet corn, expressing the CryIA(b) toxin, was compared to non-Bt sweet corn in field trials in 2006. When no treatment was made to the non-Bt sweet corn, 100 percent of the plants were damaged. Damage to ears was about 40 percent less in Bt transgenic sweet corn compared with sweet corn without the Bt transformation. However, the use of Bt transformed sweet corn alone was not sufficient to prevent unacceptable damage. When neem and the fall armyworm virus (SfMNPV) virus was used, damaged was reduced to around 15 percent. In general, spinosid (Spintor) treated plots had less than 1 percent CEW larva per 100 ears sampled. One of the key factors limiting the consistent success of entomopathogens as microbial control agents is their sensitivity to sunlight. In many cases, field-applied pathogens and nematodes lose at least 50% of their original activity within 1-2 days. The ultimate goal of this research is to identify plant derived materials that can
improve the efficacy of microbial agents against important caterpillar pests of agricultural crops and forests. In a separate study the target pest was the beet armyworm (BAW), Spodoptera exigua, an important pest on crops such as bell peppers, celery, lettuce, cotton and other crops. The microbial agent, a nuclepolyhedrovirus (SeMNPV), is specific for this insect pest. Sixty five different plant species were tested in the laboratory for their ability to protect the insect virus from breakdown by UV radiation. Twenty seven of the plant extracts demonstrated excellent protection from UV radiation. Extracts of 35 different spices from 15 plant families were tested with enhancing the activity of the virus (LdMNPV) of the gypsy moth, Lymantria dispar, a serious pests of forests. The activity of LdMNPV was not affected in 29 virus/spice combinations, whereas 6 virus/spice combinations (NPV/cayenne, NPV/curry, NPV/dill, NPV/nutmeg, NPV/paprika and NPV/tarragon) enhanced the activity of the
virus against gypsy moth larvae. These findings indicate that several of these spices enhance the action of insect microbial control agents. We found over 60 species of insects and other arthropods associated with 6 species (Echinacea purpurea, E. pallida, St.JohnsWort, FeverFew, Tansy and Valerian) of medicinal plants. When Echinacea was planted as a companion plant next to FeverFew, predators that resided in the FeverFew moved over to the Echinacea and significantly reduced the numbers of whiteflies on the latter. This is the first demonstration that companion or banker plants can reduced whiteflies in medicinal plants to non-economic levels without using chemical pesticides. The two-spotted spider mite, Tetranychus urticae, is a serious pest of watermelon and several other vegetable crops. We identified watermelon germplasm from Citrullus colocynthis, a wild-type melon, that has resistance to the spider mite. This germplasm may be a useful source of resistance to spider mites in
watermelon. In subsequent studies, damage by broad mites was reduced in Citrullus colocynthis.
Impacts
Increased public awareness of nutrition and other health benefits from the consumption of vegetables has increased vegetable production. In order to produce a high quality product, the vegetable industry relies upon routine and excessive applications of pesticides to control pests. Over 240 million pounds of pesticides, costing over 480 million dollars annually are used in the Southeast to control vegetable pests. At the same time, Brassica (collards, cabbage, etc.) crop acreage increased in Lexington County from 1,000 hectares in 1996 to nearly 4,000 hectares at present. Results from this project have already reduced use of chemical pesticides in these crops from 14 applications of synthetic chemical insecticides to three to four applications of biological control materials. This approach is being extended to other vegetable and specialty crops. Techniques developed under this project also will be adopted by organic farmers where the market for organic production is
increasing 20 percent per year. Reducing pesticide use helps farmers reduce production costs, pesticide residues, run-off into water supplies, and minimizes the effects on non-target and beneficial insects and microbes. A Field Guide for growers has been published and distributed and field days to extend the technology have been carried out. Millions of dollars have been spent on gypsy moth control. Identification of alternatives to chemical pesticides, reported herein, could have a major impact on forest ecosystems, reducing run-off into streams and other water sources.
Publications
- Shapiro, M., B. M. Shepard and R. Lopez. 2007. Effect of spices upon the activity of the gypsy moth (Lepidoptera: Lymantriidae) nucleopolyhedrovirus. J. Entomol. Sci. 42: 84-91.
- Lopez, R., A. Levi, B. M. Shepard, A. M. Simmons and D. M. Jackson. 2005. Sources of resistance to two-spotted spider mite (Acari: Tetranychidae) in Citrullus spp. HortScience. 40: 1661- 1663.
- Francis, R. L., J. P. Smith and B. M. Shepard. 2005. Integrated Pest Management for Cabbage and Collard: A Growers Guide. Clemson University Publication No. EB-156. 31 pp.
|