Cotton Insect Newsletter Vol. 21, No. 7, July 2, 2003 Call 1-877-629-1474 for Cotton Insect Hotline

Cotton Situation:  It rained again last night.  Looks like most cotton fields were recipients of the moisture that came from the remnants of Bill (the tropical storm).  I measured 1 inch in my personal rain gauge in Florence, and the weather map on the internet showed some areas got as much as 5 inches.       I traveled below the lakes to look at some cotton on Monday.  I saw my first blooms in a field in Orangeburg County.  Plants have begun squaring in a large proportion of cotton fields this week, but there are a substantial number of late-planted fields that won't be squaring for a while.   Robert Graham, the State Statistician, reported that by the week ending on June 29, 27% of the crop was squaring.  He reported that the 5-year average rate of squaring was 50% for the same time frame. Hotline:  I apologize for the problems we have been having with the Hotline.  It was down for several days, and I didn't discover it until I was trying to record last Friday's update.  Then, it was Monday before we could get it up and running again.  We will try harder to keep it running and will continue to update the message on Tuesday and Friday mornings. IC-97:  The cotton insect control recommendations are shown in the Clemson University Extension publication “Cotton Insect Management”, IC-97.  Be sure that you have the latest edition which was  revised in April 2003.  It is blue, by the way, while last year's model was yellow.   Insect Situation:  Budworms flared up a bit last week, but numbers of eggs and worms appear to be down this week.  In Bt-cotton, budworms are of little concern, since the toxin will kill close to 100%.  Conventional cotton needs to be monitored closely, however, especially where plants have begun squaring.  In cotton that has not begun to bloom, an insecticide treatment may be needed when 15 small larvae are found or there are 20 damaged squares per 100 plants.  When beneficial counts are high and no large worms (1/4 inch) are found, cotton may be able to withstand somewhat higher worm counts.   Stink bugs are being reported in some cotton fields.  Most of the reports have mentioned brown stink bugs were the most prevalent species present.  Keep in mind that stink bugs are not known to be a pest of cotton prior to blooming.  In other words, they don't appear to be damaging squares or terminals, as plant bugs are apt to do.   When blooms appear, it will be time for scouts to start checking small bolls for damage.  Randomly collect at least 25 quarter-sized bolls, preferably more, and crush them between thumb and forefinger, or slice them with a knife.  Examine the inner boll walls for signs of warts and water-soaked puncture marks.  After a few days, the damaged seeds will appear shrunken and lint will become discolored.  If 15% or more of the bolls are damaged, an insecticide treatment would be  warranted.  Be sure to check the same sized bolls each time you visit a field.   Stink bug numbers can also be used to determine if an infestation is hurting the crop.  Use a beat cloth to check for adults and large nymphs.  Carefully lay the cloth on the ground between the rows, then grab an armful of plants on each row and shake over the cloth.  Count the stink bugs that fall on the cloth.  Do it quickly because the adults won't stay around long.  Check at least 10 beat-cloth samples in a field, which would amount to about 30 feet of row.  The economic threshold is 1 stink bug per 6 row feet.  I also like to use a plastic pan (10 inches wide x 12 inches long x 5 inches deep) to check for stink bugs.  Just walk beside a row of cotton beating the plants into the pan at the rate of two beats per sample.  Take 25 such samples in four different locations in a field. There have been several reports of cotton fleahoppers and tarnished plant bugs this week.  These bugs like squares and they are certainly going to be attracted to cotton fields when their wild host plants become undesirable.  In fact, there has been an area-wide research effort in Mississippi over a number of years to try and control tarnished plant bugs by spraying their wild hosts with herbicides to prevent reproduction.  Tarnished plant bugs don't pose such a threat to South Carolina growers, but they do need to be watched by scouts.  Numbers can be estimated using a beat cloth, a sweep net or a plastic pan as mentioned above.  The square retention rates are also an important part of the equation when assessing damage by plant bugs.   Reports of slugs attacking cotton were off by a shell.   These slimy little mollusks were feeding some on cotton leaves, but since they had shells we will have to refer to them from now on as snails.  It was the first time that I had seen snails (in numbers) attacking cotton.  Some plants had as many as five snails stuck to both the bottoms and tops of leaves.  Damage was light and controls would not have been worth pursuing. There were more reports of beet armyworm egg masses on the tops of cotton leaves this week.  Reports came from Blackville, Sellers and Florence areas.  So far, no controls have been applied.   Mitchell Roof  Extension Entomologist

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