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Title: WATERMELON STAND ESTABLISHMENT: PLANTING DATES AND PREEMERGENCE HERBICIDES

Author
item Webber Iii, Charles
item SHREFLER, JAMES - OSU, LANE RESEARCH CENTER

Submitted to: Proceedings of Horticultural Industry Show
Publication Type: Proceedings
Publication Acceptance Date: 2/2/2001
Publication Date: 1/5/2001
Citation: WEBBER III, C.L., SHREFLER, J.W. WATERMELON STAND ESTABLISHMENT: PLANTING DATES AND PREEMERGENCE HERBICIDES. PROCEEDINGS OF THE 20TH ANNUAL HORTICULTURAL INDUSTRY SHOW. 2001. P. 112-114.

Interpretive Summary: Watermelons planted in the early spring can be adversely affected by cold soil temperatures which can decrease watermelon germination, slow seedling emergence, and reduce watermelon plant populations. Research was conducted in southeast Oklahoma to determine the effects of planting dates (soil temperatures) and herbicides on watermelon plant populations. 'Allsweet' watermelon seeds were planted on raised beds with 6-ft centers at 4 planting dates (April 12, April 26, May 17, and May 31) in the spring of 1999. The herbicide treatments included ethalfluralin at 1.125 lb ai/a (1X) and 2.25 lb ai/a (2X), halosulfuron-methyl at 0.025 lb ai/a (1X), 0.05 lb ai/a (2X), and 0.075 lb ai/a (3X), bensulide at 4 lb ai/a with naptalam at 2 lb ai/a (1X), bensulide at 8 lb ai/a with naptalam at 4 lb ai/a (2X), PCC-170 at 1.05 lb ai/a (1X) and 2.10 lb ai/a (2X), and a herbicide-free treatment. Soil temperatures ranged from 51 deg F for the first planting date to 70 deg F for the fourth planting date. Final watermelon stands increased significantly with each succeeding planting date, increasing from 24% to 88%. Only halosulfuron-methyl at the 2X and 3X rates significantly decreased watermelon stands compared to the herbicide-free treatment. Halosulfuron-methyl at 0.05 lb ai/a (2X) decreased stands by 22% and halosulfuron-methyl at 0.075 lb ai/a (3X) decreased stands by 27% compared to the herbicide-free treatment. Herbicides did not reduce watermelon stands at any of the planting dates, if applied at the recommended rates (1X). The provides valuable information to evaluate the risks involved in selecting earlier planting dates and the extent watermelon seeding rates would need to be increased to compensate for decreased stands as affected by the earlier colder planting dates.

Technical Abstract: Watermelon (Citrullus lanatus), weeds, and herbicides interact with the environment to affect both initial and seasonal growth, establishment of watermelon and weeds, herbicide efficacy, and crop injury. Research was conducted at Lane, OK to determine the effects of planting date (soil temperatures) and herbicides on watermelon stand establishment. Certified watermelon seeds, cv. 'Allsweet', were planted on raised beds with 6-ft centers at 4 planting dates (April 12, April 26, May 17, and May 31) in the spring of 1999. The preemergent herbicide treatments included ethalfluralin at 1.125 lb ai/a (1X) and 2.25 lb ai/a (2X), halosulfuron-methyl at 0.025 lb ai/a (1X), 0.05 lb ai/a (2X), and 0.075 lb ai/a (3X), bensulide at 4 lb ai/a with naptalam at 2 lb ai/a (1X), bensulide at 8 lb ai/a with naptalam at 4 lb ai/a (2X), PCC-170 at 1.05 lb ai/a (1X) and 2.10 lb ai/a (2X), and a herbicide-free treatment. Soil temperatures (2-in depth) at and just following planting ranged from 51 deg F for the first planting date, April 12, to 70 deg F for the fourth planting date, May 31. Final watermelon stands increased significantly with each succeeding planting date, increasing from 24% to 88%, for April 12 to May 31, respectively. Herbicides did not significantly reduce watermelon stands at any of the planting dates, if applied at the recommended rates (1X). The effects of planting date and herbicide treatments on stand establishment for individual planting dates provide valuable information to evaluate the risks involved in selecting earlier planting dates. The results also provide insight into the extent watermelon seeding rates would need to be increased to compensate for decreased stand establishment as affected by the earlier colder planting dates.