Cotton Insect Situation No. 16 August 9, 2001 Blake Layton Extension Cotton Entomology Specialist Area Specialists: Dr. Gordon Andrews Dr. Scott Stewart Dr. Mike Williams Cotton Insect Hotline: 1-800-445-4931 Last Newsletter for 2001: This will be the last regular issue of the Cotton Insect Situation Newsletter for the 2001 growing season. However, we will continue to update the Cotton Insect Hotline on a weekly basis through the end of August (1-800-445-4931). The Mississippi State Cotton Entomology Web Site is accessible year round at www.msucares.com/insects/cotton. Back issues of this newsletter are posted on this site along with other information on cotton insects and their management. Crop Situation: The Weather and Crop Report for the week ending August 6 indicated that 98% of the crop was setting bolls, and 2% of the crop had open bolls. Seventy four percent of the crop was rated as good to excellent. Statewide average temperatures were one degree above normal and statewide rainfall averaged 0.13 inches below normal. Overall, the state has a very promising crop, at least in terms of yield. Many fields have better than average boll loads, but with around 1.7 million acres of cotton in the state this year, some of it is planted on marginal ground. Bt Cotton Publication Available: We have a limited number of copies of the USDA publication "Bt Cotton And Management of the Tobacco Budworm-Bollworm Complex". This 36 page color publication includes information on how Bt cotton works, how it was developed, efficacy and economics of Bt cotton, potential for resistance, and resistance management issues. You can request a copy of this publication by calling the Department of Entomology (662-325-2085) and asking for it by name. Mississippi Entomological Association Annual Meeting: The MEA Annual Meeting will be held on November 7 & 8 at the Bost Extension Center at Mississippi State University. This is a very informative meeting that focuses primarily on research and issues affecting row crop entomology in Mississippi. For more information about this meeting call the Department of Entomology (662-325-2085). Insect Situation: For the remainder of the season one of the most important insect management concerns will be deciding when to stop protecting a crop from insects. It’s easy to waste money by spraying a crop too late, but its also easy to sustain heavy yield loss by stopping too early. Having information on when a field first reached NAWB = 5 and the number of DD60s that have accumulated since then can be very helpful in making this important decision. August is the month when we often see the highest numbers of the most pests. Late maturing fields, whether they are Bt or non-Bt, need to be scouted carefully for all pests. Boll Weevil Eradication: During the week of July 26 through August 1 no boll weevils were caught in pheromone traps on 96.5% of all Mississippi cotton fields. So far this year only 13080 boll weevils have been caught in the state, and only 5.8% of the fields in the state have required treatment for boll weevils. Even though boll weevil numbers are down, there still are boll weevils in the state, and it is normal to see populations, and movement, increase in August. The criteria for treatment of fields continues to be based on pheromone trap captures (two or more weevils per field for fields of 40 acres or less) or on confirmation of in field reproduction. Because of this last criterion, it is extremely important that any fields where live boll weevils or boll weevil egg-laying punctures are detected be reported to BWEP personnel immediately! When in doubt about whether what you have found really is a boll weevil or an egg laying puncture, go ahead and call! At this point it is much better to error on the side of caution! Names and phone numbers of the different work units and officers in charge are shown in the table below.   Boll Weevil Eradication Program Work Unit Offices Region Office Phone Number Officer in Charge 4 Aberdeen 1-800-355-6786 Arlon Cox 3 Taylor 1-888-287-8037 Mark Ferguson 3 Kosciusko 1-800-400-3321 Charles Rogillio 3 Bolton 1-800-375-2782 Danny Meyers 2 Rolling Fork 1-877-788-9444 Mike Mullendore 1B Cleveland 1-800-297-1680 Doris Sprouse 1A Inverness 1-800-269-9930 Maury Hull 1A Marks 1-800-997-9914 James Burgess   What is the last date I can expect to set a pickable boll? The answer to this question really depends on the year and where in the state you are located! The table below provides a general summary of the probability of accumulating enough DD60s to mature a white bloom that appears on the indicated date. This information is based on the average of 28+ years of historical weather data. As for when to terminate treatments for budworm and bollworm on "late" crops, the last population of effective bolls still needs to be protected from damaging populations until they have accumulated 350 to 400 DD60s. At an average of 20 DD60s per day, that’s 18 to 20 days. This means that some late crops could potentially require protection until after Labor Day.   Latest Date When a White Bloom has an 80% or 50% Probability of Accumulating 750 DD60s                   Location 80% Probability by October 1 50% Probability by First Frost Holly Springs August 2 August 11 Stoneville August 12 August 26 Jackson August 15 August 28 Adapted from graphs provided by Dr. Gordon Andrews Tarnished Plant Bug Efficacy Trial: The following table provides preliminary results of a trial recently conducted against tarnished plant bugs. This trial was conducted against an extremely heavy population of nymphs in cotton that had not been previously treated with insecticides. Because nymphs are less mobile than adults, this is the most desirable stage with which to work in small plot trials. All treatments were applied on August 1, using a CO2 powered back pack sprayer calibrated to deliver 10 GPA total volume. Thanks to Tucker Miller for his assistance in setting up this trial.                              Treatment & lbs/ ai/acre 2 Days After Treatment 5 Days After Treatment Avg. No. Nymphs Per 20 plants Percent Control Avg. No. Nymphs Per 20 plants Percent Control Untreated 16.3 -- 25.0 -- Centric 0.047 8.5 48% 4.5 82% Orthene 0.5 9.3 43% 3.5 86% Steward 0.11 11.0 32% 9.0 64% Vydate 0.33 6.8 58% 9.2 63% Karate 0.04 6.5 60% 9.0 64% Orthene 1.0 4.0 75% 2.8 89% Bidrin 0.5 2.0 88% 1.3 95%   Insecticide of the Week: Trade Name and Formulation: Methyl Parathion 4EC Common Name: Methyl parathion Producer: Cheminova Chemical Class: Organophosphate Target Pest(s): Stink Bugs Use rate range: 0.5 lbs ai Toxicity (rat/oral LD50 of technical product): 6 mg/kg For many years "methyl" was the most heavily used cotton insecticide in Mississippi. When it was first introduced, in the 1950s, it was used primarily for control of boll weevils and aphids. After tobacco budworm began to develop resistance to the organochlorine materials, it became more important for worm control, and methyl parathion alone, at 1.0 lbs ai/acre, or as a tank mix with EPN was a standard for caterpillar control during the very late 60s and most of the 70s. Even after tobacco budworms developed resistance to methyl parathion and pyrethroids became available for worm control, methyl parathion continued to see heavy use against boll weevils. "Methyl" at "1 to 16" (0.25 lbs ai/acre) was, and continues to be, highly effective against adult boll weevils, and it was cheaper than most alternative boll weevil treatments. In areas where boll weevils populations were high, it was not uncommon for individual growers to make 6 to 10 applications of methyl parathion per year. Despite this heavy repeated use, boll weevils never developed resistance to methyl parathion. Apparently, they just don’t have the genes for it. Use of methyl parathion has dropped drastically in recent years due to the statewide Boll Weevil Eradication Program. Malathion, another organophosphate and another Cheminova product, was chosen for use in the BWEP, primarily because of environmental advantages. Methyl parathion is still labeled for use in cotton, as Methyl 4EC or as Declare 4EC, but it is only available in 15 gallon or 55 gallon containers. Currently, the most important use for methyl parathion is for stink bug control, and it is recommended at 0.5 lbs ai/acre (1 gallon to 8 acres) for this pest. It’s easier to get good stink bug data from soybeans than from cotton. The graph below compares the efficacy of methyl parathion to that of several pyrethroids against southern green stink bugs (rates are given as lbs. Ai/acre). Southern Green Stink Bug Control on Soybeans The information in this newsletter is provided for educational purposes only. Mention of specific products or trade names does not imply their endorsement above other products that are labeled and recommended for a similar use. Southern Counties - Don Parker: Whitefly and stink bug densities are increasing in the southern areas of the state. Spider mite densities are increasing in some southern and central areas. Several areas have reported difficulties controlling bollworms feeding under stuck bloom tags. Frequent rains and rank growth increase the difficulty of getting the insecticides to the target insect. Northeast Counties - Mike Williams: Cotton is beginning to near cutout in many fields in North Mississippi. Flowers are easily observed from the road indicating that flowering is high up in the plants. Counts show that many fields are at 3-4 nodes above white flower. The rain showers, brought by the storm, were really welcomed and have helped to set the crop. There are still a few areas which are extremely dry. Our primary concern still remains 'bugs'. Stink bugs are still being seen in treatable numbers in some counties. We have also seen an increase in bollworm egg lay, but one consultant indicated that many of the eggs either were not hatching or the small caterpillars were dying soon after hatch. Check low in the plant on bloomtags and bracts of squares, blooms and bolls. It may be very important that we do whole plant scouts for the next few days. The upper level high winds which resulted from Barry could bring us some unwelcomed guests from the south. In years past after hurricanes have hit the gulf coast, we have seen outbreaks of fall and beet armyworms. The idea is that the winds may blow them north ahead of the weather front. Check carefully around boll bracts for window-paning and look in blooms for caterpillars. Our pheromone trap captures are also indicating an increase in beet armyworm activity in some areas. Delta and southern hill counties especially have increased numbers in pheromone traps. Bollworm numbers are still slightly elevated, as well, in most areas. We continue to have weevil capture reports from BWE and while they are low, they are still bothersome. A good cold winter should bring weevil activity to an end in NE Mississippi. This has really simplified insect management in our area. We are on target for making a minimum insecticide input crop with less than 3 applications on most acres. We certainly need to hang in there and continue to remain vigilant so that nothing slips up in August, but keeping the hi-boy parked seems to be the order of the day.   Avg. No. Moths/Trap/Week County Budworms Bollworms Beet Armyworms Boll Weevils Attala 12 72 3 0 Bolivar 5 18 75 0 Calhoun 4 28 1 0 Chickasaw 6 2 0 0 Choctaw 6 52 0 0 Clay 14 21 3 0 Coahoma 19 21 30 0 Hinds 0 11 2 0 Holmes 1 25 11 0 Humphreys 7 40 118 0 Issaquena 0 23 110 0 Lafayette 2 7 0 0 Lee 39 35 0 0 Leflore 17 34 26 0 Lowndes 5 2 0 0 Madison 0 22 2 0 Monroe 26 45 4 0 Noxubee 0 0 0 0 Quitman 4 25 22 0 Sharkey 4 35 41 0 Sunflower 11 51 21 0 Tallahatchie 7 57 6 0 Tunica 11 22 9 0 Union 8 27 1 0 Warren 0 6 0 0 Washington 5 15 3 0 Webster 2 43 0 0 Yazoo 2 43 157 0   Delta Counties - Gordon Andrews: Most cotton fields in the Mississippi delta are only susceptible to defoliators, stinkbugs, and fall armyworms. A few late fields that have received irrigation and rainfall have not cutout. These late fields seem to be attracting plant bugs from corn, soybeans, and cotton that is more mature. Late cotton gets expensive! In places where insecticide worked the adult populations are building back rapidly. Tall cotton, which still has 6-7 nodes from white bloom to terminal, is the place where plant bug control is most difficult. Plant bug nymphs are present in this tall cotton but good control from insecticides is being seen in shorter cotton in the same field. In the previous newsletter it was reported that vial tests conducted by USDA scientists are showing resistance to pyrethroids. Further tests have shown that field collected plant bugs showed some tolerance to some organophosphate insecticides. In these same vial tests orthene and vydate showed no signs reduced effectiveness. In late cotton it is time to start thinking about how much time we have left to set a boll. A bloom on the 15th of August will accumulate 750 DD60’s by September 21 if it receives 20 DD60’s a day (nighttime low 70 and daytime high 90). To pick the August 15 bloom we will need a hot September.

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