Cotton Insect Newsletter Vol. 18, No. 13,  August 16, 2000 call 1-877-629-1474 for Cotton Insect Hotline

Cotton Information:  There are more ways to obtain timely information on cotton insects this year.  There is the Cotton Insect Hotline (see the phone number above), which is updated on Tuesdays and Fridays.  This means of communication was established with financial assistance from the South Carolina Cotton Board.   I have been writing Cotton Insect Blurbs since the 1998 season.   These are timely messages that are transmitted through the Clemson University Cotton Listserver.   If you sign up for this, you will receive information as email messages.  I also appreciate the replies that I have received via email concerning the insect situation in your particular areas of the state.  The Cotton Insect Newsletter is now available through the internet at http://www.clemson.edu/peedeerec/ .  When you access the page, select Research & Extension Programs to get to the Cotton heading.  Selecting Cotton Insect Newsletter will take you to the current newsletter; selecting Cotton will take you to the archived newsletters.  The archived newsletter selection now contains Volume 18, Numbers 1-13.   We are in the process of adding newsletters from the 1998 and 1999 seasons.  The current  newsletter should always be available at our web site by the end of the work day on the same day that it is written.  Cotton Situation: Much of the cotton has reached the point of cutout, with just a few squares and blooms left in the terminals.  A major question always comes up this time of year.  What is the latest date for a bloom to become an open boll capable of being harvested?  Generally, we think of August 31 as the cutoff date for blooms to have a realistic chance of making bolls that would contribute to yield.  Phil Bauer with USDA, ARS did some work in 1995 and 1996 to look at fiber properties of normal and late-planted cotton.  During the course of his study, blooms were marked and monitored at different dates to determine the length of time for bolls to develop and open.  He found that in 1995, August 9 blooms opened in 50 days (main-stem node 6) while August 30 blooms (main-stem node 12) took 75 days to open.   This gives you some idea of the good fortune that is needed to harvest bolls made late in the season.  In other words, during a year like 1995, late August blooms might not open until mid November.   Of course there will be variation from year to year, with more heat units accumulating in some years during the late summer and fall to speed up the process.  Even when the weather man cooperates in September and October, there is always the chance of an early-November frost.  Insect Situation: Bollworms seem to be the main insect problem this week, although numbers are nothing like we saw in July.   Late-planted cotton is still attractive to moths, and they are still laying some eggs there.   Stink-bug numbers are down in most of the fields that I have looked at recently.  Growers should be most concerned about the fields that haven’t been treated with insecticides for some time, if at all.  I am beginning to see moderate populations of stink bugs in soybeans, where pods are beginning to develop.  There still have been no major outbreaks of beet armyworms reported.  Aphid numbers have remained low in most areas of the state. Boll Protection: How long do bolls need to be protected from insects?   The answer will vary depending upon the insect species that are involved in a particular field.   Unfortunately, many of the scouts that we have depended upon to tell us what’s out there have already left, or soon will be leaving to go back to school.   Without timely insect scouting information, it’s difficult to determine how to go about protecting those hard-earned bolls.  Often that job is left to the farmer and his family, or the farm crew.  The most obvious problem is that of worms feeding on bolls.  Bollworm and fall armyworms are the biggest offenders in that regard.  Bolls that are 25 days old are relatively safe from attack from bollworms.  Although fall armyworms are considered to be capable of penetrating bolls slightly older than 25-days old, their damage to such bolls should be minimal.  By the time bolls are 25 days old, the innards are not as moist and tender as in 15-day old boll.  When bollworms or fall armyworms penetrate soft green bolls, they will more than likely destroy entire bolls.   Even if they don’t eat that much, microorganisms are capable of rotting the remains.  If you can’t slice a boll easily with a knife, it’s a pretty safe bet that a bollworm or fall armyworm won’t be able to eat its way through the boll either.   When they do attempt to feed on such bolls, the damage will often be superficial and may only involve one lock.  Stink bugs tend to lose interest in bolls that are no longer soft and easy to compress between your thumb and forefinger.   Research has shown that the cutoff point in boll age is about 18 days.  At this point a stink bug offered no other choice would more than likely go for it, but if smaller bolls were available, it would not.  In summary, one should be primarily concerned this time of year with protecting small bolls from bollworms, fall armyworms and stink bugs.   The later it gets in August, the greater the number of such bolls it will take to make a pound of lint.  If it takes twice (or more) as many of these bolls to yield as much as first position, lower bolls, why should we use the same threshold to apply insecticides?  For example, if we were looking at 5% damaged bolls in Bt cotton (April or early May plantings) as a threshold for bollworms in mid-July, an appropriate threshold for mid-August bolls might be 10% or more.  In June planted cotton, 10% may be an unacceptable loss, because you are basically trying to make the bulk of a crop in August.   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.