West Plains
IPM Update

news about integrated pest management in hockley and cochran counties
Kerry Siders, EA-IPM
(806) 894-2406 (phone)
(806) 638-5635(mobile)
(806) 897-3104 (FAX)
E-Mail: k-siders@tamu.edu   http://lubbock.tamu.edu/ipm  
Vol. 6, No. 13
1212 Houston Street, Suite 2, Levelland, TX 79336
August 21, 2001

* General Situation
* Cotton
* Sorghum
* Sunflowers
* Nematode Sampling


Cotton Situation
Heavy rains in portions of Hockley County have caused regrowth problems. Be careful with any irrigation at this point. Boll rot has been noted in more and more cotton fields. Cotton bollworm activity increased this week. Cotton boll weevil movement from field to field continues. A few headworms have been noted in grain sorghum. Greenbugs are being held in check by beneficials.

COTTON
A majority of the cotton crop in Hockley and Cochran counties has an average of 1.8 nodes above white flower (NAWF) with a range of 0-4.7 NAWF. Based on actual heat unit accumulations, from National Weather Service observer data, the cotton acreage which cut-out (< 4 NAWF) prior to August 3 has accumulated over 350 heat units (DD-60's). These acres should be safe from cotton boll weevil damage to this years crop.

Cotton acres which cut-out prior to July 25 have accumulated over 550 heat units. These fields should be safe from further larval pest damage. I have checked many fields which cut-out prior to the 27th by cutting bolls and have confirmed that these heat unit estimates of maturity are holding true.

Cotton bollworms have arrived in some isolated areas. The more "growthy" cotton has been receiving the most pressure and allowing for survival. However, most of the cotton acreage has less than 2 nodes above white flower or has bolls to the top; and worm survival been extremely low. I have seen a few fields at 6,000-12,000 small worms per acre drop to levels of less than 3,000-4,000 worms per acre in 2-3 days. The threshold which should be applied at this time for worms is 10,000-12,000 per acre. Also, check to make sure if these small worms (<1/4 inch) are surviving more than 2-4 days. Call if you have questions.

Cotton Boll Weevils are moving from field to field now. It is extremely important that you are checking your fields. We should now be checking small dime-nickle size bolls. I suggest that when that last boll cannot be easily cut with a knife then it is safe. If there is time to mature smaller bolls, boll protection is warranted when 15 percent of these small bolls are weevil damaged and there are at least 2-3 vulnerable, undamaged, potentially harvestable bolls found per 10 row feet of cotton plants examined (based on $0.75 per pound cotton lint).

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At lower priced cotton you should use a higher threshold of say 4-6 vulnerable, harvestable bolls per 10 row feet. As I have already mentioned, we have some acres safe from boll weevils, however the later cotton will be vulnerable through September. Remember the Eradication Program will take over responsibility for weevil control the first week of September. Some products labeled for use to control weevils are: Guthion, methyl parathion, Vydate, Phaser, Thiodan, and Penncap M. Remember, prices vary, labels should be followed and all worker protection restrictions should be adhered to.

Cotton aphids continue to be found at extremely low numbers in very few fields. We continue to find banded wing whiteflies in some fields, but not at treatable levels. Lygus have increased dramatically the past several days. This is possibly due to increase in late season weed pressure and movement out of maturing peanut fields. Lygus damage to later cotton should be watched closely.

Cotton Boll Rot
Xanthomonas boll rot has been noted in several fields over the past month. This disease results from the same bacterium noted on foliage all season from bacterial blight. In the boll -rot phase of bacterial blight, lesions on bolls tend to be circular, dark green, and water-soaked or greasy when young. Two or more lesions often become confluent. Spots rapidly become sunken, brown, and dry in the center with a dark-red margin, and attain a diameter of about 3/8 inch. The causal agent, Xanthomonas compestris a true parasite, but is an exception to the rule that true parasites can breach the unbroken cuticle of the boll. X. campestris does, however, penetrate stomata, or enters through nectaries; it is conveyed by spattering droplets of rain, or carried by insects. Once within the boll, the bacteria multiply rapidly, killing and causing collapse of tissues, and spreading through the mass of developing fiber.

Affected locks fail to fluff out. This results in spots of yellow fiber that my cause reduced grade. The drier weather this week has definitely helped slow this down and has limited its spread; however, sprinkler systems can continue the incidence of this disease. Make note of fields which have boll rot and note the variety. Certain varieties are more susceptible and it can be transmitted by seed.

SORGHUM
Sorghum pests have been relatively light on early- planted milo, more activity has been noted in late-planted milo. Continue to check for headworms, greenbugs, and midge. Beneficials remain fairly high.

SUNFLOWERS
Sunflowers continue to be visited by head moths. Keep a particularly close watch on late sunflowers.

REMEMBER
This is a good time of year to sample soil for nematodes. This can help with next year's decisions about at -plant nematicides.

UP COMING EVENTS

September 19th - West Texas Ag Chem Conference, Lubbock

September 20th - Farm & Home Show Hockley County, Levelland

September (To Be Announced) - Farm Fair Cochran County, Morton

 

West Plains IPM Update is a publication of the Texas Agricultural Extension Service IPM Program in Hockley and Cochran Counties.

Editor: Kerry Siders
Production: Patty Castaneda



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