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Field and Forage Crops |
Finally, we're seeing the kind of heat and humidity conducive to rapid cotton growth. Given the late start, however, heat units and timely rainfall patterns will need to be good to excellent from here on for a successful 2005 cotton crop. Any actions that producers can take to avoid maturity delays are strongly encouraged.
Thrips appear to be hanging around particularly late this year with a combination of an early cool spring, a late cotton crop, and recent hot weather. Although our cotton crop is finally showing some signs of life, most of it has not reached the 5 true leaf stage and is still vulnerable to thrips damage. If we can just get past this odd thrips season, insects may give us a break for a while on most of the cotton acreage. Scouts should begin checking for cotton aphids and spider mites and, from about mid June to early July, for second-generation budworms on non-Bt cotton.
With hot, dry conditions occurring in many areas of the state, spider mites are occurring in scattered locations (in a few cases in high numbers). Mites often show up along field borders, though this week's reported infestations appear to more randomly scattered within fields. Their presence can most easily be confirmed with a hand lens focused on the undersides of speckled yellowish or purplish leaves. A lot of mites on the undersides of leaves, coupled with easy-to-find eggs may indicate an active population or expanding population. Lower leaf defoliation is often an indication of a serious mite outbreak. Observations a few days apart in the same field location may allow one to recognize a declining population, particularly if small, fungus-laden, grayish mite carcasses are found along with limited levels of mite eggs. A timely, significant rainfall may help speed up the establishment of these pathogens. Fortunately, less than 1 to 3 percent of North Carolina's cotton acreage is treated for spider mites in a typical year. Unfortunately, spider mites can be a real problem for those who have economic infestations. Control sometimes translates into 1 to 2 foliar applications of an expensive, marginally effective insecticide, especially in the event of extended dry, hot conditions.
Although cotton aphids can occur in seeding cotton, build-ups are typically more common in blooming cotton. Fortunately for scouts and producers, cotton aphid colonies usually need to reach very high levels on droughty cotton before economic damage occurs. As is often the case at this time of year, reports of cotton aphids have been almost non-existent so far. However, remember that cotton aphids are present in most cotton fields in low numbers and populations can increase quickly when conditions are favorable, sometimes seeming to occur in significant numbers almost out of thin air. In 2004, approximately 12 percent of North Carolina's cotton acreage was treated for cotton aphids.
With any luck, both spider mites and cotton aphids will be minor pests in 2005. We should be about two weeks away from any potential plant bug damage or from second-generation tobacco budworms on non-Bt cotton.
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, 2005 by Stephen J. Toth, Jr.