Cotton Insect Newsletter Vol. 20, No. 4, June 12, 2002 Call 1-877-629-1474 for Cotton Insect Hotline

Hotline:  I'm using the “Cotton Insect Hotline” to supply you with timely information on the cotton insect situation.   The recorded messages are updated on Tuesday and Friday morning (by 9:30 AM).  This service is sponsored by the South Carolina Cotton Board.   The toll-free number is  displayed in the upper right-hand corner on the front page of every “Cotton Insect Newsletter.”   Cotton Situation:  Where moisture has been adequate, plants have started growing rapidly.   Cotton plants start out slowly, giving the impression they will never increase in size, then almost overnight they go through a growth spurt.   Where plants were badly damaged by thrips and soil moisture has been inadequate, it's going to take some rain to help initiate any kind of “spurt.” Cotton plants are squaring, or soon will be, in the majority of cotton fields.  The first squares on a plant will usually appear in the leaf axil (where the leaf joins the main stem) between nodes 5 and 8 about 45 days after planting.   Full-season varieties will tend to set squares at least one node higher than early-season varieties.   If first squares are being set at node 9 or higher, there is a problem.   Plants that set first-position squares at higher nodes will tend to produce rank vegetative growth.  Although there are several factors that could influence plants to set squares at higher positions, in my experience these fields generally tend to have high plant populations.   An average of two-to-three plants per foot of row would be considered ideal, but you will occasionally see fields with an average of 6-8 plants per foot of row.   Plants growing under such conditions will tend to be spindly, they will be late squaring, and they will produce fewer and smaller bolls per plant.   Insect Situation:  A few bollworm and budworm eggs and small larvae can be found in conventional cotton fields this week.   In Bt cotton, most scouts will be hard-pressed to find any worms, but they will probably find some eggs in terminals if they look hard enough.  With populations of predators, such as big-eyed bugs, increasing it won't be a bad thing to have a little food to keep them interested in staying on the cotton plants.   Natural enemies are very useful in Bt cotton fields in keeping bollworm and armyworm numbers at sub-economic levels. Grasshoppers continue to be of concern to some farmers.   Nymphs take some time to develop to adults, so they can potentially feed for 40 days or more, then the adults will hang around for quite a while unless chemicals are employed to shorten their lives.  Why are we getting so many grasshoppers these days?  I can't really tell you why, but they do tend to run in cycles, and I'm hoping this year will mark the end of the current cycle. Besides the grasshoppers, a number of new insects have started showing up in strip-till cotton during the last few years.   False chinch bugs are one of the most common new bugs on the block.   Nymphs may feed on seedling cotton plants, and both nymphs and adults will just about cover up some of the plants.   Later in the season, adults may be found on cotton leaves and in squares.  The burrower bug, is a close relative of the stink bug.  It has piercing-sucking mouthparts and feeds on stems and roots of many wild plant species.   Occasionally, these insects will move over to cultivated plants such as cotton when they have been deprived of their preferred host plants.  These insects look a little like small black stink bugs.   Like stink bugs, the tips of the membranous wings are visible.  The negro bug is similar in appearance, but slightly smaller (about 0.15 inch in length, the burrower bug is 0.25 inch in length) and the shell-like wing covering, or scutellum, completely covers the membranous wings.  Cutworms show up more often in strip-till fields, especially where burn-down is delayed until shortly before planting.  Thrips seem to be less of a problem in strip-till cotton, especially when cotton is planted in rye or wheat stubble.   Although there may be some insect problems that are somewhat unique to cotton grown under conservation-tillage practices, I certainly would not discourage anyone from utilizing these good farming practices to try and avoid insect problems.  Most of these pests are very minor players.  For example, very few acres have ever been sprayed for false chinch bugs in South Carolina.  They will rarely cause economic damage to small seedlings, but the adults don't do any harm to the plants even when you find a dozen or more in a single square.  Burrower bugs and negro bugs have rarely shown up in large numbers in cotton fields.  Grasshoppers and cutworms are probably the most important insect pests in strip-till fields, and they cost farmers relatively little when compared to the major insect pests such as bollworm and stink bug.  This is the time of year that I usually get some questions about a brown and black colored click beetle that is very abundant in cotton fields that have started squaring.  These cigar-shaped beetles are less than ½ inch in length, and they are generally found in the terminals of the cotton plant.  Infestations of these beetles will persist until about the time that plants begin to bloom.  Immatures are called wireworms, and they grow and develop in soil where they feed on the roots of plants in the grass family.  They are called click beetles for a good reason.  If you place one on its back, it will make a clicking sound and jump high in the air, often landing on its feet.  This is one of those insects that don't seem to be doing anything in a cotton field other than to use the plants for a rest stop.  They may also be getting nourishment from the nectaries which are located on the leaves and squares of the cotton plants.                        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. The Clemson University Cooperative Extension Service offers its programs to people of all ages, regardless of race, color, sex, religion, national origin, disability, political beliefs, sexual orientation, marital or family status and is an equal opportunity employer.  Clemson University Cooperating with U.S. Department of Agriculture and South Carolina Counties.  Issued in Furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of May 8 and June 30, 1914.  Public Service Activities