Progress 09/01/05 to 08/31/08
Outputs
OUTPUTS: Objective: To evaluate the effectiveness of synthetic and a living mulch with and without a reduced-risk insecticide to mosaic viral diseases of zucchini. Whiteflies, Bemisia tabaci, B-biotype (Homoptera: Aleyrodidae) is a key pest in zucchini squash, (Cucurbita pepo L) causing both direct and indirect damage. In a field experiment, we investigated the effect of mulches alone or in combination with a reduced-risk insecticide, imidacloprid (Admire 2F) on whiteflies and their related problems in zucchini squash. UV-reflective mulch and the living mulch, buckwheat (Fagopyrum esculentum Moench), with and without imidacloprid were evaluated in a completely randomized block design with four replications. White mulch (standard) was included as a control in the experiment. Mulches in combination with imidacloprid resulted in fewer numbers of whiteflies per leaf than those without imidacloprid. More whiteflies were recorded on zucchini plants growing on white synthetic mulch than all other treatments. These plants also showed the first viral symptoms in the field, which were identified as Cucurbit leaf crumple virus (CuLCrV). Greenhouse tests confirmed the ability of whiteflies to transmit the CuLCrV. Both living and reflective mulches were more effective than white mulch in reducing the densities of whiteflies and the incidence of CuLCrV on zucchini plants. Objective. To determine the effects of reflective and a living mulch with and without a reduced-risk insecticide on marketable yields of zucchini Zucchini plants grown with reflective mulch with imidacloprid produced significantly higher yields than those from buckwheat and white mulch (control) treatments. Reflective mulch alone and white mulch provided similar yields. Buckwheat plots produced the least yields when compared with all the other treatments. Objective: To survey cucurbit fields in Florida for the presence of cucurbit leaf curl virus (CuLCV), a new whitefly transmitted geminivirus that was discovered in Florida during the first phase of the project. Three cucurbit farms located in three different counties Marion, Putnam, and Hernando were sampled for Cucurbit leaf crumble virus. Scouting for symptoms was done by walking every row and visually observing plants for virus symptoms. We did not record any plant viruses in Hernando County. However, the farms in Putnam and Marion Counties had plant viruses. Both yellow and zucchini squash plants were observed to show mosaic, mottling and reduced leaf lamina, common virus symptoms. Symptomatic leaves were picked and submitted to the Plant Disease Clinic at the University of Florida, Gainesville. The samples were analyzed for the presence of a begomovirus using WTG hybridization assays. These samples tested negative for a begomovirus and positive for a Potyviridae virus. The potyviridae was not one of the commonly occurring viruses such as Papaya ringspot virus, Zucchini yellow mosaic virus and Watermelon mosaic virus. PARTICIPANTS: Dr. Jane Polston - Plant Pathology, University of Florida Dr. Susan Webb - Vegetable Entomology, University of Florida University of Florida's Plant Disease Clinic TARGET AUDIENCES: Project was developed to find sustainable alternatives to pesticides for cucurbit growers to manage viral diseases in Florida. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The study identified a viral disease, Cucurbit leaf crumble virus that was not reported in Florida cucurbits. The study suggest that the use of living or reflective mulch alone or in combination with imidacloprid can be used to reduce whitefly populations and reduce the incidence of Cucurbit leaf crumble virus-infected squash plants. There are additional benefits to be derived by combining a living mulches with a reduced-risk insecticide such as Admire 2F.
Publications
- Akad, F., S. Webb, T. W. Nyoike, O. E. Liburd, W. Turechek, S. Adkins, and J. E. Polston. 2008. Detection of Cucurbit leaf crumple virus in Florida. Plant Dis. 92. 648.
- Liburd, O. E., T. W. Nyoike, C. A. Scott. 2008. Cover, border and trap crops for pests and disease management In: J. L Capinera (Ed.). pp. 1095-1100. Encyclopedia of entomology 2nd Ed. Vol. 1 A-C. Springer, Netherlands.
- Liburd, O. E., and T. W. Nyoike. 2008. Biology and management of whiteflies in sustainable field production of cucurbits. ENY-848/IN762, IFAS Extension, University of Florida, Gainesville, FL.
- Liburd, O. E., and T. W. Nyoike. 2008. Biology and management of aphids in sustainable field production of cucurbits. ENY-847/IN761, IFAS Extension, University of Florida, Gainesville, FL.
- Webb, S. E., F. Akad, T. Nyoike, O. E. Liburd, and J. E. Polston. 2007. Whitefly-transmitted Cucurbit leaf crumple virus in Florida, Fact Sheet ENY-477 (IN716), IFAS Extension, University of Florida, Gainesville, FL.
- Nyoike, T., O. E. Liburd, F. Akad, and J. E. Polston. 2007. Dont crumple under whitefly pressure; reflective mulch, imidacloprid can help control a new whitefly-transmitted disease. Citrus & Vegetable Magazine, November 2007.
- Nyoike, T. W., O. E. Liburd and S. E. Webb. 2008. Suppression of whiteflies, Bemisia tabaci (Hemiptera: Aleyrodidae) and incidence of Cucurbit leaf crumble virus, a whitefly-transmitted virus of zucchini squash new to Florida, with mulches and imidacloprid. Fla. Entomol. 91. 460-465.
|
Progress 09/01/06 to 08/31/07
Outputs
To test the effect of living and reflective mulches with and without a reduced-risk insecticide. Treatments were arranged in a randomized complete block design with four replications and included 1) reflective mulch with the reduced-risk insecticide Admire 2F, 2) reflective mulch without Admire 2F, 3) living mulch with Admire 2F, 4) living mulch without Admire 2F and 5) standard synthetic white mulch (control). Adult whiteflies and aphids were counted from the leaves in-situ by leaf-turn method. In addition, adult whiteflies were monitored with yellow sticky traps for six weeks. Also, leaf discs were collected from 9 plants in each plot for immature whiteflies. In-situ counts indicated that plants growing within plots treated with living and reflective mulch had significantly fewer adult whiteflies per leaf than those growing over white mulch. The addition of Admire 2F to the buckwheat treatment resulted in further reduction of whiteflies per leaf. White mulch had
significantly higher numbers of immatures per leaf disc compared with all other treatments. A positive correlation between SSL index and whiteflies immatures was observed. Yellow sticky traps placed within the white mulch caught significantly more whiteflies per trap than all other treatments. Aphids were monitored using blue and clear water pan-traps or six weeks. Foliar counts indicated that none of the treatments were better than the others in protecting zucchini plants from alate aphids. Pan traps within the white synthetic mulch caught significantly more alate aphids than those in buckwheat alone and reflective mulch treatments. Reflective mulch alone was the most effective in protecting squash plants from alate aphid infestations. b) Effect of living and reflective mulch with and without Admire 2F to insect-transmitted viruses. Visual observations of viral symptoms and incidences were recorded and monitored in the field. Plants showing viral symptoms had one leaf excised from
the young leaves and transported to the laboratory where the leaves were assayed for virus infection using ELISA test and PCR. Zucchini leaves tested positive for begomovirus identified as Cucurbit leaf crumple virus (CuLCrV). Buckwheat and reflective mulch treatments gave a better protection from CuLCrV than white mulch. Addition of Admire 2F to reflective and buckwheat treatments resulted in a decrease in the number of plants showing virus symptoms. c) Impact of living and reflective mulches with and without Admire 2F on plant size and marketable yields of zucchini squash. Ten plants were randomly selected from the inner rows. Plant height and width were recorded and yield data were collected from the three inner rows of each plot. Squash plants growing within buckwheat mulch treatments were smallest both in terms of width and height compared with all other treatments. The addition of Admire 2F to the mulches only affected plant height within the buckwheat treatment alone.
Reflective mulch plots had significantly higher yields than all other treatments including the white mulch (control). Addition of Admire 2F did not enhance yields in reflective or buckwheat treatments.
Impacts
The development of cultural and chemical control strategies for whiteflies and aphids in zucchini that are environmentally friendly and yet economically feasible to growers. Standard grower practices used white plastic mulch and scheduled calendar insecticide sprays to manage whiteflies and aphids in the production of zucchini. The aim is to demonstrate to growers that they can reduce their reliance on conventional pesticides and still achieve good marketable produce as indicated in our study.
Publications
- S. E. Webb, F. Akad, T. W. Nyoike, O. E. Liburd, and J. E. Polston. 2007. Whitefly-transmitted cucurbit leaf crumple virus in Florida. EDIS. UF/IFAS, University of Florida, Gainesville. IN716.
- Liburd, O. E., T. W. Nyoike, C. A. Scott. 2007. Cover, Border and Trap Crops for Pest and Disease Management. New Edition, Encyclopedia of Entomology. Kluwer Academic Publishers, Dordrect, The Netherlands.
|
Progress 09/01/05 to 09/01/06
Outputs
Florida is one of the leading cucurbit producers in the USA. Whiteflies (Bemisia tabaci Biotype B) and aphids are significant insect pests of cucurbits in Florida. Whiteflies transmit Gemini viruses and cause physiological disorders on squash, which is associated with the feeding of the immature whiteflies. Aphids are important vectors of plant viruses and they transmit devastating viruses. These viruses are transmitted in a non- persistent manner. The overall goal of this study is to develop cultural and chemical control strategies for whiteflies and aphids in zucchini that are environmentally friendly and yet economically feasible to growers. To investigate the use of reflective and a living mulch (buckwheat) with and without a reduced-risk insecticide for controlling aphids and whiteflies Field plots measuring 10.4 m x 10.4 m were established at the University of Florida, Plant Science Research Station, Citra, Florida. The following treatments were evaluated: 1)
reflective mulch with the reduced-risk insecticide Admire 2 F (Bayer, Kansas City, MO), 2) reflective mulch alone, 3) living mulch with Admire 2F, 4) living mulch alone, and 5) a standard synthetic white mulch (control). Treatments were arranged in a randomized complete block design with four replications. We recorded significantly fewer numbers of adult whiteflies on yellow sticky traps in treatments that had reflective with Admire, reflective alone and buckwheat with Admire compared with the control. Leaf disk counts in the laboratory indicated that the control had the highest number of immature whiteflies and that most of the immatures were concentrated in the lower plant stratum. As far as aphids are concerned, only treatments with admire 2 F had significantly fewer aphids than the control. To study the effects of reflective and living mulch (buckwheat) with and without a reduced-risk insecticide on natural enemies (beneficial insects) Natural enemies were sampled using in-situ
counts from treated plots with zucchini plants. Six leaves from six plants located on the outside rows of each plot were randomly selected and the number of natural enemies recorded. Significantly more natural enemies were recorded on plants treated with buckwheat + Admire 2 F than control. There was no significant difference among the other treatments. To determine the effects of reflective and a living mulch in combination with and without a reduced-risk insecticide on marketable yields of Zucchini Fruits from the three interior rows were harvested to obtain the yield data. The harvested fruits were weighed and graded according to Florida standards for marketable zucchini. Highest marketable yields were obtained from plots treated with reflective mulch with admire 2 F and reflective mulch alone. Buckwheat alone, as well as those treated with admire 2 F produced significantly fewer marketable zucchini than the control. Overall, buckwheat plots had more natural enemies but this did
not translate into fewer numbers of whiteflies and aphids compared with other treatments. Competition for plant resources (mineral salts, water space) may have contributed to the reduced yields in buckwheat plots.
Impacts
The overall goal of this study is to develop cultural and chemical control strategies for whiteflies and aphids in zucchini that are environmentally friendly and yet economically feasible to growers. Standard grower practices used white plastic mulch and scheduled calendar insecticide sprays to manage whiteflies and aphids in the production of zucchini. The aim is to demonstrate to growers that they can reduce their reliance on conventional pesticides and still achieve good marketable produce as indicated in our study.
Publications
- No publications reported this period
|