Cotton News Letter Vol. 18, No. 4,  June 14, 2000

Cotton Situation: Cotton is growing well in most areas of the state, despite the fact that moisture has certainly been limited. The cotton planted in mid April is now squaring freely and should be putting on some blooms in the next week to 10 days.  I think most of the cotton that is going to be planted has been.  Square retention counts will be useful during the next few weeks.  Examine a pinhead-sized square at the base of the newest unfolded leaf in a terminal and determine if the square is set or shed.  If shed, a square may appear grey in color, or it may be green, but when lightly touched it falls off.  Examine at least 25 plants, but preferably 50-100. Cotton plants should be setting 90-95% of the pinhead squares.  Where retention is lower, an insect pest could be the culprit, because few squares will shed from physiological stresses during the first 2-3 weeks of squaring.  Insect Situation: There hasn't been much insect activity this week.  This has given most growers the luxury of concentrating on some other needs, such as side-dressing their nitrogen and killing weeds. There were some reports of false chinch bugs on seedlings.  Budworms appear to be out in force, both in tobacco and now in cotton.  Stink bugs have been seen in cotton, although there shouldn't be any problem this early in the season. False chinch bug numbers seem to be on the increase during the last few years.  Last year there were many reports of high numbers of nymphs and adults on seedling cotton. This year there have been about as many reports, but I haven't actually seen any infestations in fields that I have checked.  In most of the fields that I visited last year, the bugs did not seem to be doing any economic damage.  I saw the highest numbers where cotton was planted with minimum tillage and there was a ground cover consisting of wild plants that had been burnt down with a herbicide . I counted as many as 75 on a tiny cotton seedling.  When temperatures are high and soil moisture is extremely low, they can cause some damage, and even kill some plants. But this would be the exception, not the rule.  In most cases, after plants get a couple of true leaves and start growing normally, the false chinch bugs don't seem to do much damage. They are apparently sucking some sap from the stems and leaf petioles, but they don't appear to damage small squares.  In fact we often see a dozen or more inside a large square where there has been no apparent damage.  At any rate, we don't have any insecticides expressly labeled for false chinch bug control.  There have been some stink bugs found in cotton during the past week. I'm not surprised by this, nor am I alarmed.  In the first place, stink bugs cause most of their damage by feeding on small bolls.  I won't say there are absolutely no small bolls for them to feed on, but we don't expect much activity until about the middle of July.  At that time a scout would be well advised to begin checking small bolls for damage.  Stink bugs are probably not going to do any economically important damage to squares. If you are seeing any pinhead to match-head sized squares that appear to be damaged by insects, then you should suspect either plant bugs or small bollworms, and you should scout the field accordingly.  The most likely stink bug that you will encounter at this time of the season is not even a pest. It is a beneficial insect. The spined soldier bug often moves into cotton fields about the time that squaring begins. This is a predaceous insect that feeds readily on bollworms and budworms.  It is similar in color to the brown stink bug (a crop pest), but it does have somewhat sharper points on the shoulders, the beak is somewhat thicker, and the body is a bit narrower than that of the brown stink bug. Leaf miners are common in cotton fields every year.  The damage appears as whitish to yellowish winding trails on the surfaces of leaves resulting from the feeding of fly larvae within the leaf tissue.  I saw some reports of economic problems from leaf miners from California many years ago.  They stated that the problem was worse under drought conditions, at which time there was a considerable amount of lower leaf shedding.  Infestations were brought under control by rainfall or irrigation, and in some cases insecticides were applied.  It is conceivable that there could be some problems in areas of the state with extreme drought, but it is very unlikely that an insecticidal intervention would be warranted for leaf miners. There has been some egg laying in cotton by budworm and bollworm moths this week.  I received one report out of Darlington County where 69% of the eggs were tobacco budworm.  At this time scouts should be looking for worms in terminals as well as making egg counts to determine the numbers of eggs per 100 plants.  There should not be any worms surviving to cause economic problems on Bt cotton in June. The toxin should be close to 100% effective against budworms and bollworm control should be close to that.  Most problems with bollworms in Bt cotton arise from worms getting started on blooms in the lower parts of the plants. Bollworms feeding on terminals and in squares should experience a high mortality rate. Boll Weevil Containment: Don't be alarmed if you aren't seeing any boll weevil traps around your cotton fields. With the exception of a few fields in Lexington County, where the 3 weevils were trapped last year, traps are still in the boxes.  On Friday June 16, Randal Lynch and his supervisors will instruct their field workers to begin putting up pheromone traps.  They plan to have completed the installations by July 13.    Mitchell Roof Extension Entomologist

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