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Field and Forage Crops |
Reports continue to confirm the fact that many areas of the state are experiencing stink bug levels on cotton here that are probably unprecedented. Most consultants and scouts who have been checking blooming cotton fields are finding internal boll damage in the single digits, with many also in the 10 to 25 percent damage range. A few fields have damaged bolls levels as high as 40 percent. Many of these are brown stink bugs, Euschistus servus, the more difficult to control species. Unfortunately, stink bugs tend to build up during the season in untreated cotton fields, so they will not be disappearing any time soon. On the plus side, we also have some areas where stink bug levels are at more reasonable levels, though not many areas. For control of brown stink bugs, Bidrin insecticide may be needed. Vydate, methyl parathion or Orthene also provide fair to good control of brown stink. With Bidrin, methyl parathion and Vydate, be especially careful in observing their labeled Worker Protection Standard guidelines, as the mammalian toxicity of all three is high. Because relatively few adult stink bugs can go along way toward damaging bolls and because even moderate levels of stink bugs can be overlooked, checking quarter-sized bolls is the most efficient to monitor bug damage and the possible need to treat with insecticide. At this time of year we recommend that producers use the 10 percent internal boll damage threshold.
Presently, very few bolls have reached the stink bug-safe age of about 3 and one half weeks, so essentially all cotton bolls are presently susceptible to stink bug damage. Also remember that although the number of total bolls within the first few days of blooming is low, bolls produced within the first 3 to 4 weeks of blooming typically constitute most, and occasionally as much as 90 percent, of the cotton crop.
Although stink bugs may not yet be a concern in all fields, our generally very high population levels across much of the state mean that the possibility of moderate to severe damage exists in many fields in the coming weeks.
As the season progresses with this early developing crop, we will be able to increase the damage threshold as the proportion of large, stink bug-safe bolls increases. But we are certainly not there yet.
Moderate to high plant bug levels are also adding to this internal boll damage. Plant bugs seem to be damaging small bolls in some fields just as soon as the pink bloom is beginning to dry. To be on the safe side, we would recommend squashing or cutting open bolls for internal plant bug damage (same as stink bug damage) within 3 to 4 days after blooming begins in those few cotton fields which will begin blooming this coming week. Cotton fields with a dirty bloom level of 15 percent or higher may also be at or near treatment with insecticide.
As predicted, the bollworm moth flight began in the southern tip of North Carolina early, with the Rowland light trap having about 150 moths on July 12. On July 15, the moth levels were well over 400 in one night in this area (very high for this time of year). We expect this bollworm flight to be both early and heavy throughout the state, with threshold levels of eggs and bollworms developing quickly. Mitch Roof reported bollworm egg counts of 80 to 100 per 100 terminals in the Pee Dee area of South Carolina (near Florence) on July 13. Many conventional cotton fields in the Scotland, Hoke, and Robeson counties will or have likely reached threshold levels during the July 14 to 20 time period, with other areas of the central Coastal Plain and points east not far behind. Consider monitoring these flights on-line at: http://ipm.ncsu.edu/cotton/insectcorner/blacklight/index.html. Additional light traps will be phased in as the bollworm season progressed during the next four weeks.
Early cotton crop maturity and cutout will be our best hope in minimizing the potential negative impact of our expected high bug and bollworm levels. But, at least for the next three or four weeks, it would pay growers to be alert and ready to respond quickly to threshold levels of bugs and worms.
Soybean aphids have been found infesting soybeans in Virginia. Some of the Virginia counties border North Carolina and I suspect the aphids are in North Carolina. Infestations in Virginia were not threatening the health of the plants due to their low population level. Soybean aphids were found in Maryland and Mississippi in 2003 and Georgia in 2004. Please watch for this insect and alert me if you think it is present in your county. This aphid is one of a few aphids that will colonize soybeans. It is yellow in color and has black (dark) cornicles (tailpipes). The soybean aphid is one of a few aphids that will create colonies on soybean plants (although I found a similar looking aphid in Chowan County last year that was later determined to be a green peach aphid). A computer search on soybean aphid will present you with many images and much information on this insect.
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 July 19, 2004 by Stephen J. Toth, Jr.
