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United States Department of Agriculture

Agricultural Research Service

Research Project: Integrated Crop, Soil, and Water Management Systems for Sustainable Production of Sugarcane for Bioenergy Feedstock

Location: Sugarcane Research Unit

Title: Preemergence weed control in transplanted watermelon - 2012

Authors
item Shrefler, Jim -
item Webber, Charles
item Brandenberger, Lynn -
item Goodson, Tony -
item Taylor, Merritt -

Submitted to: Extension Publications
Publication Type: Monograph
Publication Acceptance Date: March 15, 2012
Publication Date: April 1, 2013
Citation: Shrefler, J., Webber III, C.L., Brandenberger, L., Goodson, T., Taylor, M. 2013. Preemergence weed control in transplanted watermelon - 2012. In: Brandenberger, L. (ed.). 2012 Vegetable Weed Control Studies. Oklahoma State University, Division of Agricultural Sciences and Natural Resources, Department of Horticulture & Landscape Architecture. Stillwater, OK. MP-162. p. 7-9.

Interpretive Summary: Watermelon is a major vegetable crop in Oklahoma. Effective weed control is needed to obtain good yields of marketable fruit. Chemical weed control in this crop is crucial for commercial growers, particularly as labor costs increase and availability of hoeing crews becomes less of an option. The objectives of this study were to determine the crop safety and effectiveness of herbicides that have not previously been labeled for use in watermelon for transplanted watermelon production. Treatments in this study included Reflex (fomesafen: 0.1875, 0.25, 0.375, and 0.5 lb ai/a), Sandea (halosulfuron: 0.024 lb ai/a), and Lorox (linuron: 0.05 lb ai/a) alone and combinations of Reflex and Sandea for a total of eight treatments plus weeded and unweeded checks. Crop data that were collected included vine stunting (June 25), crop vigor (July 6), vine length (July 9), and fruit yield (Aug 28). Weed control was evaluated visually on July 6 for carpetweed (Mullugo verticillata), spiny amaranth (Amaranthus spinosus), goosegrass (Eleusine indica), crabgrass (Digitaria spp.), and yellow nutsedge (Cyperus esculentus). Lorox (0.05 lb ai/a) killed nearly all watermelon plants within about 10 days after transplanting. Most herbicide treatments provided 90% or greater control of each of these weeds. The exceptions were as follows. Sandea (0.024 lb ai/a) alone gave 81% control of carpetweed, 30% control of goosegrass, and 37% control of crabgrass. Reflex at the lowest rate (0.1875 lb ai/a) gave 86% control of yellow nutsedge. Stunting of watermelon by some treatments was detected on June 25 when plants had reached a 5 inch height with 4-5 leaves. Although some reduced crop growth was observed early in the crop cycle, the reduced crop growth was not accompanied by yield reductions. The treatments that resulted in the greatest stunting and lowest vigor also produced some of the greatest fruit yields. No yield differences were detected among treatments, excluding Lorox that killed the watermelon plants. With the exception of Lorox, the authors see no indication that the herbicides pose a serious injury hazard to transplanted watermelon when used at the rates reported in this trial.

Technical Abstract: Watermelon is a major vegetable crop in Oklahoma. Effective weed control is needed to obtain good yields of marketable fruit. Chemical weed control in this crop is crucial for commercial growers, particularly as labor costs increase and availability of hoeing crews becomes less of an option. The objectives of this study were to determine the crop safety and effectiveness of herbicides that have not previously been labeled for use in watermelon for transplanted watermelon production. Treatments in this study included fomesafen (0.1875, 0.25, 0.375, and 0.5 lb ai/a), halosulfuron (0.024 lb ai/a), and linuron (0.05 lb ai/a) alone and combinations of fomesafen and halosulfuron for a total of eight treatments plus weeded and unweeded checks. Crop data that were collected included vine stunting (June 25), crop vigor (July 6), vine length (July 9), and fruit yield (Aug 28). Weed control was evaluated visually on July 6 for carpetweed (Mullugo verticillata), spiny amaranth (Amaranthus spinosus), goosegrass (Eleusine indica), crabgrass (Digitaria spp.), and yellow nutsedge (Cyperus esculentus). Lorox (0.05 lb ai/a) killed nearly all watermelon plants within about 10 days after transplanting. Most herbicide treatments provided 90% or greater control of each of these weeds. The exceptions were as follows. Halosulfuron (0.024 lb ai/a) alone gave 81% control of carpetweed, 30% control of goosegrass, and 37% control of crabgrass. Fomesafen at the lowest rate (0.1875 lb ai/a) gave 86% control of yellow nutsedge. Stunting of watermelon by some treatments was detected on June 25 when plants had reached a 5 inch height with 4-5 leaves. No yield differences were detected among treatments, excluding linuron that killed the watermelon plants. With the exception of linuron, the authors see no indication that the herbicides pose a serious injury hazard to transplanted watermelon when used at the rates reported in this trial.

Last Modified: 10/1/2014
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