Bertie County Farmline

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1 North Carolina Cooperative Extension March 2015 Bertie County Farmline Richard W. Rhodes County Extension Director Contact Us For more information regarding any of your farming needs, please feel free to contact our office at Your questions and concerns are important to us. Bertie County Cooperative Extension Ag Information Line By calling Bertie County farmers can hear the 7-day weather forecast. This information is updated daily beginning April 13, 2015 and will run until the cold weather threat to cotton planting has ended this spring. Burndown Herbicides For Roundup Resistant Weeds Horseweed, also called marestail and the pigweed specie Palmer amaranth are two weeds found in Bertie County that are resistant glyphosate. Infestations of these two resistant weeds are wide spread in the county. Horseweed emerges in the fall. It will be a rosette stage and large enough for identification by early March. It is critical that glyphosate-resistant horseweed be controlled before planting cotton; options to control this weed after Roundup Ready or conventional cotton emergence are very limited. Tank mixes of glyphosate plus 2 pints of 2,4-D that has 3.8 lbs. active ingredient per gallon or glyphosate plus 0.5 pint of Clarity can control glyphosate-resistant horseweed. The tank mix with 2,4-D should be made at least 30 days ahead of planting. Many but not all brands of 2,4-D are labeled for application 30 days ahead of planting cotton (Check Label). Cotton planting must be delayed at least 21 days after the accumulation of 1 inch of rainfall following Clarity application. This often means a four to six week delay between Clarity application and planting. Although injury to cotton is possible from either 2,4-D or Clarity applied in a cold and dry spring. We have not had the dry but we have had the cold weather. However, research to date in North Carolina has shown no problem when the above guidelines were followed.

2 Burndown Herbicides For Roundup Resistant Weeds Continued Horseweed normally germinates in the fall, but additional plants may emerge in late spring. These spring-germinating plants will not be controlled by previously applied 2,4-D or Clarity. Valor has poor postemergence activity on horseweed; hence adding Valor to glyphosate will not improve control of emerged plants. However, Valor has preemergence activity on horseweed. Valor included in a tank mix of glyphosate plus 2,4-D or Clarity will reduce problems with late-emerging horseweed. Weed scientists in Tennessee have found that Cotoran applied preemergence is probably the best option to control late-emerging horseweed. Gramoxone should be included with the Cotoran to kill emerged weeds at the time of planting. Although somewhat less effective than a tank mix of glyphosate plus 2,4-D or Clarity, a mixture of Gramoxone plus Direx will adequately control horseweed if the mixture is applied when daytime temperatures exceed 70 degrees F. Gramoxone plus Direx plus crop oil concentrate should be applied 15 to 45 days ahead of planting. This treatment can also be made after planting prior to crop emergence. Ignite 280 at 29 ounces per acre will also control horseweed if applied when daytime temperatures exceed 75 degrees F. Ignite 280 is an option to control spring-emerging horseweed at planting time or in situations where growers have failed to follow one of the programs outlined above. Ignite 280 can be applied anytime prior to cotton planting or during planting. It is critical that Ignite 280 be applied under warm conditions. In addition, research by Dr. A lan York s has shown the application of Liberty needs to be delayed until 2 hours after sunrise and no later than 1 hour before sunset. Weed control is drastically reduced if these application recommendations are not followed. Sharpen herbicide is very effect on horseweed but needs to be applied 42 days ahead of planting cotton and 1 inch of rain needs to accumulate during this time to avoid crop injury. This may not be a real choice this year for cotton growers given the weather delays in getting burn-down herbicides out this year. Palmer amaranth is a very aggressively growing pigweed species common in many cotton fields in Bertie County. Most of the Palmer amaranth encountered in the county is now resistant to glyphosate and to the A L S herbicides lik e S taple and Envok e. In this situation, there are no overthe-top herbicide treatments for controlling Palmer amaranth in Roundup Ready cotton; one must get control by using an effective burndown program that would include Valor, followed by an equally effective preemergence program. This weed grows very rapidly (1 to 2 inches per day) and may reach six to eight feet tall by cotton harvest. Palmer amaranth is highly competitive with cotton; it is very prolific and can produce over 400,000 seed per female plant, and it has long been considered one of our worst weeds in cotton. Growers must take this threat seriously. That means undertaking an aggressive program to control existing resistant populations to slow further spread and a proactive weed control program to reduce further selection for resistant Palmer amaranth biotypes. The 2015 Cotton Information Book on page 130 provides suggested herbicide programs to control Palmer amaranth in cotton.

3 Cotton Planting Decisions Current research conducted in North Carolina indicated cotton yields begin to drop to below early planting levels around 40 days after April 29, which would be after June 10. This data suggest that optimum planting date should be shifted later than earlier. Planning to complete by May 31 should provide a long planting period and an insurance period should replanting be needed. Cotton planting should be completed by June 10 to achieve full yield potential. Deciding when to plant will depend on the weather conditions during mid to late April, since cottonseed is very sensitive to cool soil temperatures during germination. When the cottonseed is absorbing water to begin germination, soil temperatures below 50 F can cause chilling injury and the cottonseed can die if temperatures dip to 41 F. Temperatures below 50 F at about two day after planting may either kill the seedlings or cause growth retardation for weeks into the season. Cotton producers could start planting after April 15 if soils temperatures are 65 F at a 3-inch depth by 10 a.m., and warm, dry weather is predicted for the next 5 to 7 days. Rapid germination occurs at soil temperatures above 70 F and is very slow at temperatures below 60 F. The risk of poor or spotty germination when planting in cold soils is greatly increased under wet conditions. Planting conditions are considered excellent if greater than 50 DD-60s (degree F Max + degree F Min Temp)/2 60= DD-60s) accumulate for the 5 days after planting. Avoid planting cotton if the low temperature is predicted to be below 50F for either of the two nights after planting. See following table. Richard W. Rhodes County Extension Director Bertie County Center North Carolina Cooperative Extension 106 Dundee Street, PO Box 280 Windsor, NC Phone: (252) Fax: (252) richard_rhodes@ncsu.edu North Carolina State University and North Carolina A&T State University commit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age, or disability. In addition, the two Universities welcome all persons without regard to sexual orientation. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

4 NC Cooperative Extension Bertie County Center 106 Dundee Street PO Box 280 Windsor, NC RETURN SERVICE REQUESTED

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