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Field and Forage Crops |
Adult thrips have continued to decline this week, although continued dry weather in many areas of the state and residual thrips infestations have resulted in some foliar insecticide applications. Areas with moderate rainfall and recent cooler weather have fared well, with some cotton now into the 5 or 6 true leaf stage and out of harm's way. This has probably been a record year for thrips for North Carolina cotton producers in terms of the numbers of foliar insecticide applications directed at this pest.
Spider mite populations appear to be increasing in several of the northeastern North Carolina counties, at least in part due to the significant spraying for thrips. Expect spider mite levels to become problematic if weather patterns become hot and dry again (or remain dry). On the other hand, if we are fortunate enough to get generous, soaking rainfall, a fungal pathogen will often reduce mites to sub-treatment levels. Spider mite treatments are often expensive and less than satisfactory. I advise refraining from applying foliar insecticide sprays until general leaf discoloration (yellow spotting, followed by bronzing) is common, mites are present throughout most of the field, and defoliation is present in approximately 25 percent or more of the field. If rainfall is likely, refrain from spraying and reevaluate after 2 or 3 days. A hand lens can come in handy when looking for spider mite adults, immatures and eggs, primarily on the undersides of leaves.
Our weather patterns and early budworm levels on other crops and in other states suggest that these caterpillars may be at high levels and early this year. The earliest budworm infestations on cotton that I can recall were around June 10, so cotton scouts should begin terminal and square evaluation now. A reasonable guess might be to expect initial budworms to begin showing up around June 15 in Scotland, Robeson and Hoke counties.
This season's first cotton scouting school will be held on June 19 at 9:00 a.m. at the O. P. Owens Agriculture Center in Lumberton. If traveling on Interstate 95, take the Pembroke exit. Contact Georgia Love (telephone: 910-671-3276; electronic mail: georgia_love@ncsu.edu) for details.
Thrips continue to infest peanuts throughout the production areas of North Carolina. The threshold for follow-up foliar sprays remains at a level when 25 percent of the newly-opened leaflets show significant thrips injury. This threshold is based upon the direct impact of thrips feeding on the peanut plant and is not related to the transmission of tomato spotted wilt virus.
It is my understanding that several experts are recommending the use of insecticide sprays for thrips control as a means of reducing tomato spotted wilt virus. If someone recommends the use of a foliar spray to reduce tomato spotted wilt virus, ask to see the supporting studies and data that demonstrate these sprays help. All of the practices found to be effective in reducing tomato spotted wilt virus in peanuts either are utilized prior to or during planting. Unless the thrips populations are high enough to threaten the crop (greater than 25 percent of the new leaflets with damage), save your money.
Watch for sites with early season spider mite injury. It is still a bit early, but with as warm as its been and with the mild winter and spring, it is certainly possible we could see spider mites in peanuts by late June if the weather does not help us. Scout the traditional locations where mites are often seen.
Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Last modified on June 13, 2002 by Stephen J. Toth, Jr.
