INSECT, PLANT DISEASE, & WEED SCIENCE NEWS [No. 88-19] [August 5, 1988]

In This Issue: Late Season Weed Control in Corn and Sorghum Bindweed Control Where Wheat is to be Planted Double Crop Soybeans August Lawn Renovation Late Season Weed Control in Corn and Sorghum Late season broadleaf weed control in corn and sorghum is possible with 2,4-D. Such a treatment could make harvesting easier and reduce weed seed production. Treatments should be applied no later than flowering stage of weeds for control of seed production. Both corn and sorghum can suffer yield reductions from 2,4-D applied during the flowering period. As a guideline, 2,4-D use on corn can be resumed after the silk turns brown. The use of 2,4-D on sorghum can be resumed after the grain reaches the early dough stage. Sorghum should not be sprayed with 2,4-D between the beginning of head emergence and the milk stage of the grain. These late 2,4-D treatments will not cause lodging or stalk brittleness in the crop. Bindweed Control Where Wheat is to be Planted Fall is usually an excellent time to make herbicide applications for field bindweed control. However, healthy new growth on the bindweed is essential for good results. Avoid tillage for at least 30 days prior to treatment. Dry weather in some areas has reduced bindweed growth making it more difficult to control. It would be best to wait for rain and new bindweed growth before treating. This could be too late this fall for land going to wheat. September treatments are usually more effective than August treatments. Double Crop Weed Control The early wheat harvest and high soybean prices have prompted some growers to double crop soybeans this season. The biggest concern is controlling volunteer wheat. Both Fusilade 2000 and Poast can be used but slightly higher rates are required compared to annual grasses. Use 1.5 pt./A of Poast with either DASH or COC plus 1/2 gallons of 28% nitrogen per acre. Fusilade 2000 should be used at 1 pt./A with COC or a nonionic surfactant. Broadleaf weed control options are similar to conventional soybean production with the exception that some weeds may be too tall for effective control with postemergence products. In addition, the dry weather may reduce herbicide effectiveness. Check labels to see which surfactants should be included. Avoid long residual herbicides such as Scepter or Classic unless you\u27re prepared to go back to soybeans next spring. August Lawn Renovation August is the time to get started with turf renovation. Roundup is a useful herbicide for such projects. Skip one or two mow1ngs so there\u27s good growth on the weeds and grass for herbicide intake and activity. Apply 2 ½ to 3 oz. of Roundup/1000 sq. ft. using 1 gal or less of water. Delay vertical mowing, slicing, coring, and power raking for 7 days