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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED PEST MANAGEMENT SYSTEMS FOR CONVENTIONAL AND ORGANICALLY PRODUCED VEGETABLE CROPS Title: Watermelon foliar fungicide timing trial

Authors
item Shrefler, Jim - OSU, LANE, OK
item Goodson, Tony - OSU, LANE, OK
item Bruton, Benny
item Damicone, John - OSU, STILLWATER, OK

Submitted to: Oklahoma Agriculture Experiment Station Departmental Publication
Publication Type: Experiment Station
Publication Acceptance Date: December 2, 2007
Publication Date: January 15, 2008
Citation: Shrefler, J., Goodson, T., Bruton, B.D., Damicone, J. 2008. Watermelon foliar fungicide timing trial. In: Brandenberger, L. and Wells, L. editors. 2007 Vegetable Trials Report. Oklahoma State University, Division of Agricultural Sciences and Natural Resources, Department of Horticulture & Landscape Architecture. Stillwater, OK. MP-164:37-38.

Interpretive Summary: Foliar diseases are a persistent threat to watermelon production in Oklahoma. The diseases anthracnose, downy mildew, and powdery mildew can result in yield and fruit quality losses when foliage is damaged. Effective fungicides are available for control of these diseases. However, growers are faced with the challenge of determining when to apply to obtain maximum effectiveness. One means to determine fungicide application is the anthracnose forecaster which is internet based and available on the Oklahoma Mesonet weather system. This trial was conducted to compare the efficacy of two broad spectrum fungicide treatments (1. Dithane 75DF/Topsin 70WP tank mix or 2. Bravo Weatherstick) using application timings based on a 14-day schedule or the anthracnose forecaster model. Downy mildew was the predominant disease that developed in mid-season and completely defoliated the non-treated control within 7 days. Regardless of biweekly or forecaster-defined applications, disease control was similar. However, the Dithane + Topsin treatment was more effective than Bravo in the first three weeks of the disease epidemic. Although these fungicides are not the most effective for downy mildew control, they did provide sufficient protection to allow for other more disease-specific fungicides to be applied. This study demonstrated that using a predetermined bi-weekly application or using the anthracnose forecaster model can be effective for early stages of downy mildew. One additional benefit of the forecaster model is the possibility of using fewer sprays to obtain similar control.

Technical Abstract: Foliar diseases are a persistent threat to watermelon production in Oklahoma. Several diseases that include anthracnose, downy mildew, and powdery mildew can result in yield and fruit quality losses when foliage is damaged. Effective fungicides are available for the control of these diseases. However, growers are faced with the challenge of determining when to apply to obtain maximum effectiveness. One means to determine fungicide application is the anthracnose forecaster which is internet based and available on the Oklahoma Mesonet weather system. This trial was conducted to compare the efficacy of two broad spectrum fungicide treatments (1. Dithane 75DF/Topsin 70WP tank mix or 2. Bravo Weatherstick) using application timings based on 14-day schedule or the anthracnose forecaster model. Downy mildew was the predominant disease that developed in mid-season and completely defoliated the non-treated control within 7 days. Regardless of biweekly or forecaster-defined applications, disease control was similar. However, the Dithane + Topsin treatment was more effective than Bravo in the first three weeks of the disease epidemic. Although these fungicides are not the most effective for downy mildew control, they did provide sufficient protection to allow for other more disease-specific fungicides to be applied. This study demonstrated that using a predetermined bi-weekly application or using the anthracnose forecaster model can be effective for early stages of downy mildew. One additional benefit of the forecaster model is the possibility of using fewer sprays to obtain similar control.

Last Modified: 8/1/2014
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