Cotton Insect Newsletter Vol. 17, No. 3, May 26, 1999

Cotton Situation      There was quite a bit of replanting last week.  It looked as though some fields would have been better left alone, but once replanting has begun it seems to be hard for a grower to make the decision to not replant a field.       Soil temperatures have warmed nicely resulting in some rapid emergence.  Cotton should begin growing at a more rapid rate this week, which means that thrips won't be able to damage plants like they could have when plants were growing slowly.  There's not much of it left, but cotton planted early in April may have 6 or 7 leaves on it by now. Insect Situation      We looked at lots of cotton fields last week in Lee, Darlington, Marlboro and Dillon Counties;  I believe it is safe to say that thrips were making their presence known.  Cotton was still growing very slowly as a result of cool evening temperatures, so thrips were doing their thing.  There was a considerable amount of damage being done to true leaves (upper surfaces wrinkled and distorted, with some leaf margins curled up).  Terminal buds were also showing the results of being stabbed and sucked on by thrips.       About 50% of the fields that I checked would have qualified for foliar sprays.  In one field, which had been replanted in Lee County (where the great majority of April-planted cotton fields were replanted), there were 4-5 adult thrips per plant.  These plants were still in the cotyledonary stage!  It was obvious that a soil insecticide was not used during replanting, so a foliar spray will be needed immediately, if not sooner.      I checked some newly emerged plants here at the PDREC farm last Monday.  There were anywhere from 1 to 7 adult tobacco thrips on the undersides of the cotyledons.  No true leaves had formed.       Farmers that are replanting should be prepared to apply a foliar insecticide application with Orthene, Bidrin or Monitor as soon as plants are up to a good stand.  The soil-insecticide applied with the first planting will be used up or washed on down in the soil profile, so it won't help much against the thrips that are there now.       I mentioned in my first Newsletter that thrips were beginning to damage cotton during the first week in May.  Yes, this is a bit early.  Usually we don't expect to see much thrips action in cotton until about May 15.  Although fields of small grains are maturing rapidly, there are still plenty of thrips to come out of many of those fields.  Wild hosts, such as grasses and other plants growing in non-cultivated areas may continue to produce an abundance of thrips during the next couple of weeks.      What about thresholds?  I would go with the threshold of one or more thrips per plant on cotton plants up to the two-leaf stage.  Larger plants may tolerate two per plant or more.  Pay special attention to the tiny terminal buds.  When those babies are reduced to amorphous blobs, or turn black, you can bet that plants have already been set back 2-3 weeks, and they could even be killed if not rescued by an insecticide treatment.  We see dead plants frequently in untreated plots.  Also, be prepared to come back with another foliar spray 5-7 days after the first one.       By the time most plants have reached the 5-leaf stage of growth, thrips should no longer be a problem.  The greatest benefits from thrips control will usually accrue during early seedling development. 2ee for Vydate      I had a couple of questions this week about Vydate for thrips control.  DuPont did receive a 2ee registration for thrips control in 1999.  We have at least one on-farm test looking at Vydate for thrips control in cotton.  False Chinch Bugs      We often see false chinch bugs on cotton squares and blooms in July, but I haven't seen them attacking seedling cotton before.  Raymond Sligh emailed me a picture of some false chinch bugs attacking no-till cotton in York County.  These insects are a little more than 1/8 inch long with a dirty grayish coloration.  The immatures, which were also numerous, have some reddish markings.  Mouthparts are of the piercing sucking variety.  I will put this picture in a Cotton Insect Blurb so that you can take a look at it if you are on the Cotton Listserver.      I have heard reports of false chinch bugs damaging seedling cotton in California, but this is the first time, to my knowledge, they have caused such problems here.  Apparently the bugs were feeding on some winter annuals that were in the field prior to planting, and were able to survive until the cotton seedlings became available. Reminder      There is a $10 registration fee to attend a Cotton Scouting School in Orangeburg on June 8 or at the PDREC on June 9. Mitchell Roof  Extension Entomologist

This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. Brand names of pesticides are given as a convenience and are neither an endorsement nor guarantee of the product nor a suggestion that similar products are not effective. Use pesticides only according to the directions on the label. Follow all directions, precautions and restrictions that are listed.