Cotton Insect Newsletter Vol. 19, No. 5, June 13, 2001 Call 1-877-629-1474 for Cotton Insect Hotline

Cotton Situation: Cotton plants are growing rapidly this week.  In most areas of the state, soil moisture has been adequate to provide for this rapid growth.   I just looked at the weather map and it shows shower activity throughout most of the state today.   This weather system is made up of the remnants of tropical storm Allison.  From the circular motion of the rain clouds showing on the weather map, it looks like there could be fairly heavy rain at some locations. 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 the 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 be tend to be spindly, they will be late squaring, and they will produce fewer and smaller bolls per plant.  Insect Situation:   It seems like insects have been coming out of the woodwork so to speak, since we started strip tilling cotton, and exploring other minimum tillage situations.  One such insect is the burrower bug, which 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.  I have had one report from Calhoun County of negro bugs infesting strip-tilled cotton in numbers of 3-5 per infested plant.   I have not found any references to either of these insect species causing much damage to cotton, so I would not be to anxious about applying an insecticide unless there was evidence that some seedlings plants were being killed.    If scouts find these bugs in cotton they should quantify the numbers per plant and estimate the percentage of plants that are infested. Grasshoppers continue to cause problems in cotton fields.   If they are widespread and nibbling on most cotton plants they need to be controlled while they are still small.  Big grasshoppers tend to eat big chunks of plant material and they tend to be harder to control.  Orthene, malathion, Lorsban, Sevin, and any of the synthetic pyrethroids should provide adequate control.   Any of these products will knock down beneficial insects as well as grasshoppers.  The first serious tobacco budworm moth flight will be starting any time now.  A depleted population of beneficials in Bt-cotton wouldn’t be a problem, as the numbers of beneficials would quickly rebound and there should not be any budworms surviving on these cottons with or without beneficials.   There will, however, be a greater risk when you destroy beneficials in conventional cotton fields, because we depend on them to keep down early infestations of budworms.   Conventional cotton fields that are designated as unsprayed-refuge fields may be treated with any of the insecticides mentioned above with the exception of the pyrethroids.  Armyworms will often be found feeding on small cotton plants this time of year.   Yellow-striped armyworms have been common inhabitants of cotton fields this week, but they are rarely present in sufficient numbers to be a problem.  Beet armyworms may be found feeding on seedling cotton plants, but they are usually quickly dispatched by predators such as big-eyed bugs.  Lyme disease, although it’s not a problem for cotton plants, could affect cotton scouts.  You aren’t apt to encounter the main vector of Lyme disease, the black-legged tick, Ixodes scapularis, in a cotton  field, but you certainly run the risk of picking them up in grassy areas around the edges of fields, or next to wooded areas where there former hosts (small mammals and birds) might be found.  During their second year of life they look for larger animals to supply their blood meal, and that could be either you or a white-tailed deer.  Check yourself over carefully at the end of each day and if you find a tick remove it by grasping with tweezers as close to the body as possible.  It usually takes 2-3 days of feeding for an infected tick to transmit the bacteria which cause the disease.   An infected person will often notice a large red patch at the site where the tick was attached to the body.  This warning sign may or may not appear from 3 days to a month after being bitten. Lyme diseases may be successfully treated with antibiotics, but if the tick bite were to go unnoticed and the disease untreated, there could be serious damage to the joints (arthritic like symptoms) and to the nervous system.    Mitchell Roof  Extension Entomologist

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