Submitted to: National IPM Symposium
Publication Type: Abstract Only
Publication Acceptance Date: January 5, 2009
Publication Date: March 24, 2009
Citation: Webber III, C.L., Davis, A.R., Taylor, M.J., Shrefler, J.W. 2009. Organic weed control in watermelons [abstract]. Sixth International IPM Symposium, March 24–26, 2009, Portland, Oregon. p. 84. Technical Abstract: Integrated pest management (IPM) is an essential element for certified organic crop production and producers place weed control as their highest research priority within their IPM programs. The objective of these experiments was to investigate the impact of integrated organic weed control systems on watermelon (Citrullus lanatus var. lanatus) yields. Six watermelon varieties were transplanted at two locations (Lane, OK and Center Point, OK), into randomized complete block experiments with four replications. The seeded varieties were 'Early Moonbeam,' 'Sugar Baby,' and 'Allsweet,' and three seedless varieties were 'Triple Crown,' 'Triple Prize,' and 'Triple Star.' The weed control system at Lane utilized black plastic mulch on the crop row, while the area between rows was cultivated to control weeds. The no-till organic system at Center Point used a mowed rye and vetch cover crop, hand weeding, and vinegar (5% acetic acid) for weed control. When averaged across varieties, the organic production system at Lane produced significantly more fruit per plant (4.2 vs. 2.3 fruit/plant), greater marketable yields (35.2 vs. 18.5 lb/plants), and higher average marketable weight per fruit (13.4 vs. 8.9 lb) than at Center Point. Plants at Center Point produced a greater percentage of marketable fruit, 92%, compared to plants at Lane, 63%. When comparison was made between locations, four of six varieties had significantly greater numbers of fruit per plant and higher marketable yields at Lane than at Center Point. Except for 'Early Moonbeam,' all other varieties produced significantly heavier fruit at Lane than at Center Point. In contrast, the Center Point location produced a greater percentage of marketable fruit for all varieties except 'Allsweet.' The plastic mulch and cultivation between crop rows was a successful method of weed control at the Lane location and provided a stronger weed barrier to prevent weed growth than the cover crop mulch at Center Point. In conjunction with this research, fruit quality evaluations (lycopene and brix) determined that the fruit quality was as good or better when harvested from the weedier Center Point location. Fruit quality differences between locations may be a reflection of weed pressure, other production factors, or a combination of both. Further research will specifically investigate the impact of weed competition on watermelon fruit quality.