Cotton Insect Newsletter Vol. 20, No. 9, July 17, 2002 Call 1-877-629-1474 for Cotton Insect Hotline

Cotton Situation: We are seeing more fields on the verge of cutting out this week.  Where moisture has been particularly deficient, 16-inch tall plants are blooming out the tops.  Temperatures are expected to be in the high 90's this week, with heat indexes of 105 to 110--Very uncomfortable for scouts, and extremely dangerous for those who aren't taking care of themselves.  If you are spending lots of time in the field, be sure to take some breaks in the shade and drink plenty of water.  One of the biggest mistakes most of us make in managing heat stress is failing to drink enough water.  Or worse yet, we rely on soft drinks to supply the needed moisture.  Soft drinks may taste good going down, and they may satisfy the thirst to some extent, but when you need to get water into your system in a hurry, there is no substitute for cool, clear water.  A soft drink will still be residing in your stomach 30 minutes or more after you drink it.  Heat exhaustion, heat stroke or the old “monkey on your back” are all to be avoided.  Doctors advise drinking 8 glasses of water per day under normal conditions.  When it's hot like this, you need to double that amount.  Insect Situation: Bollworm moths are laying eggs in most areas of South Carolina this week.  They seem to be a few days ahead of schedule, since we don't usually find treatable infestations at the Pee Dee Research and Education farm until July 18 or later.  We had some plots where bollworm- egg numbers reached the treatment threshold (20/100 plants in conventional cotton varieties and 75/100 in Bt varieties) on July 12.  Most farmers have sprayed or are starting to spray their conventional cotton varieties this week in the Pee Dee area.  Below the lakes, most conventional cotton has been sprayed at least one time and some Bt-cotton fields are being treated. Scouting for bollworm eggs has been rather difficult, to say the least, where aphid infestations are moderate to heavy.  I wish I had some tips to help make the job easier, but unfortunately eggs are just more difficult to pick out among the aphids and their cast skins.  Consequently, you have to spend more time looking for eggs and worms than you would in a field that was aphid free.   I guess you could say this is another cost the farmer incurs when cotton becomes infested with aphids.  But how would you put a dollar figure on this?  Our economic threshold for aphid control isn't much good, but it's all we have right now.  We say that controls may be needed when most of the plants are heavily infested, lower leaves are shiny from the accumulation of honey dew, and plants are under severe drought stress.  Or, they may not need to be controlled.  In other words, it's up to you.  Economic thresholds for aphid control have been difficult to develop.  Most of the insecticide studies we have tried to do with aphids has been complicated by the appearance of the fungus, Neozygites fresenii.  The typical test goes like this: replicated plots are established, insecticides are applied when aphid numbers appear to be hurting the plants, we come back 3 days later and make counts, and aphids have apparently been controlled by all insecticide treatments.   The problem has been, the aphids were controlled in the untreated plots as well.   Of course, the real control agent was N. fresenii.  There is still hope for aphid research.  Drs. Sullivan and Turnipseed and a graduate student at the Edisto REC have begun a research program this year designed to develop thresholds for aphid control.   Perhaps, they will find that our present threshold is ok, or perhaps aphids are doing more damage than we think.  By the way, the fungus is showing up in some fields.  Last week, I looked at some cotton in the Pamplico area that had been treated for aphids.  There were a few aphids still alive in the untreated cotton, but 90%+ had cashed in their chips.  Where we used some Provado left from last year, control was close to 100%.  I still see some fields where the aphids have built up large numbers, but still no fungus, and very few parasites.  Several farmers have treated for beet armyworms in Darlington County.  Some have applied two or three applications already.  Tracer seems to be doing a good job at 1.4 to 1.6 oz.   Don't expect to get very good bollworm control with this rate.  There is a new product on the market called Double Threat, which combines Capture and Tracer.  This product will provide another option for growers that need to control beet armyworms plus bollworms.  Steward and Intrepid are also good materials for beet armyworm control.  Steward, which is recommended @ 9.2 to 11.3 oz/acre, would provide better bollworm control than the low rate of Tracer.  Intrepid at 4 to 6 oz/acre would be good for beets, but poor for bollworms. Earlier this year, I had discussed using a more moderate threshold for beet armyworms in cotton that was not blooming.  In cotton that is setting bolls, however, I would consider applying an insecticide when there were 5 hits/100 feet of row.   See the recommendations for the definition of a hit. Cotton Insect Control Recommendations: I'm still hearing a few farmers say they don't have the latest recommendations for cotton insect control.  You should all have the yellow-colored publication “Cotton Insect Management” IC-97.  You can also access the 2002 Pest Management Handbook at  http://cufan.clemson.edu/pestmgmtguide/.  You can get ag chemical control recommendations for all field crops in this publication.    Mitchell Roof  Extension Entomologist

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