Cotton Insect Newsletter Vol. 22, No. 12, August 4, 2004

Cotton Situation:  Alex, the first tropical storm/hurricane of the year, has brought heavy rains to coastal areas of North and South Carolina.  I'm sure many farmers are grateful for Pix this week, and there may be a few that wished they had used some.   I count myself in the latter group.   Fortunately, for us non-Pix users, our plants are loading up with bolls.  An abundance of fruit will tend to hold vegetative growth in check in most varieties, although some will still give “Jack's bean-stalk” a run for its money. Insect Situation:  Most scouts are reporting lower numbers of bollworm/budworm eggs this week.  Their reports showed egg counts ranging from single digits to 40/100 plants.  A sizeable percentage of these eggs may have been laid by budworm moths—since pheromone traps have been catching more budworm moths than would be expected at this time of year.  Mike Sullivan told me that many growers below the lakes were applying their 2nd insecticide treatments on Bt cotton this week.  Above the lakes a sizeable acreage of Bt cotton has only been sprayed once and there are a few fields with no treatments.  Bugs are damaging bolls in cotton fields throughout the state.   Below the lakes, there appear to have been fewer plant bugs this week, but stink bugs may be on the increase.  With corn plants maturing rapidly, they will no longer be desirable to stink bugs for food and shelter.   Just like people, when the kitchen is closed, stink bugs have to look elsewhere for food.   Some may gravitate toward wild host plants, while others will end up on field crops.  Cotton and soybeans are probably the most abundant and most desirable of the crops currently available for exploitation.  Where have all the stink bugs gone?  If I were a stink bug, I would be more inclined to seek food and shelter in soybeans this week.   Many cotton fields in the Pee Dee area are on the verge of cutting out.   Bolls aged 20 days or older would be too tough to poke, but there are still some tender morsels (young bolls) in the terminals.   However, if I dined on terminal cotton bolls, I would certainly be more exposed to predators (primarily birds).  Scouts would actually be able to see me in a terminal and they would immediately report my presence to the farmers.  On the other hand, soybeans are looking good and there is an abundance of vegetative growth to hide stink bugs.   Many soybean fields are just loaded with tasty pods and developing seeds.   I believe that's where I would want to go to meet my buddies (Mr. Green, Mr. Brown and Mr. S. Green).  If stink bugs are thinking the way I am, it will mean that farmers must increase their vigilance in soybeans as well as cotton.   And with better-than-average monetary returns expected in soybeans, stink bug control may be just as important as in cotton.  Scouts talk a lot about seeing stink bug damage, or “stink-bug like” damage, but there are no stink bugs or other bugs to be found.   Where are they?   Perhaps they're not even in the field.  Perhaps they leave the fields during hot days, and return at night to feed.   I'm sorry to say, however, that I have never camped out in a cotton field at night to confirm this theory.  Reports of armyworms have not increased during the last week.  It looks like cotton will not be inundated by fall armyworms, as probably would have occurred before the days of Bt cotton and the development of new and improved insecticides.   Keep looking for falls in white blooms and look for bract etching (“window-paning”) on medium to large bolls.   Mike Sullivan reported seeing some beet armyworms in one field in the Blackville area, but it was no where near an economic infestation.  Beet armyworm infestations are much more likely to occur where plants are somewhat drought-stressed and canopies are open, which is a rather uncommon situation this year.  Insect Thresholds:  As mentioned above, much of the cotton is nearing cutout.  Plants are blooming out the top, and 90-95% of the bolls that will be harvested are there.  Treatment thresholds for bollworms should be adjusted to reflect changes in the yield potential of bolls.   For example, a boll at node 18 is going to produce much less lint than one at node 10.  If the majority of the lower bolls are sizing nicely, and many are getting too tough to chew, then treating for 3 large worms or 5% small boll damage in Bt cotton would be uneconomical.   If a cotton field was planted late and has just started making bolls, then, of course the usual thresholds would apply.  Use the common-sense approach to bollworm management in August.   Mitchell Roof  Extension Entomologist

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