Web Site: http://entowww.tamu.edu
Vol. 30, No. 10

COTTON

Most cotton continues to hold at 1 to 3 nodes above white bloom. Cotton bollworms are the most predominate pest in area cotton. Last week egg counts ranged from a few thousand per acre up to 307,000 eggs per acre. Typical fields had counts ranging from 20,000 to 70,000 eggs per acre. Survival rates for larvae have not been comparable to the egg lays observed. Much of the lower survival rate is due to recent pyrethroid applications, but not in all cases. Larval counts have ranged from 0 to 32,000 per acre. In a few cases high larval survival rates were observed in fields recently treated with an insecticide. The IPM Agent in Castro and Lamb County, Emilio Nino collected a number of these surviving larvae from treated fields and we examined them to see if any were tobacco budworms. We found that all were cotton bollworms, for which we were relieved. The lack of control could be related to coverage problems in tall cotton with closed canopies. Higher gallons of water have shown to provide better control for cotton aphids and beet armyworms in the past and the same may be needed for cotton bollworm this year. In large, closed canopy cotton we recommend using at least 3 gallons of water per acre as the carrier. Smaller cotton can probably drop to 2 gallons/acre.

I have been asked about the residual of pyrethroids for bollworm control. This is very difficult to predict and will depend on many factors such as closed canopy cover, temperatures, rainfall and irrigations that wet the canopy.

In the past we have residuals as short as 7 days and as long as 21 days. Based on observations this year we may expect around 10 days for control. Because of the sheer numbers of eggs, you will find small larvae when scouting your field. If you are finding larvae 3/8" or larger, then the residual carryover of the pesticide is past and another application may be needed if medium and large "worm" counts exceed threshold. As we reach full "cut out" in fields, the bollworm larvae survival rates decline because of the lack of small fruit on which to establish. Only a few fields have reached this point and most fields have many small bolls which are still susceptible to cotton bollworm damage.

Cotton aphid counts have generally ranged from 0.2 to 10 aphids per leaf. So far our bollworm applications have not created widespread outbreaks, but we will have to keep an eye on this pest over the next few weeks.

Beet armyworms are still being found in a number of area cotton fields, but counts remain generally low and similar to the previous reporting period. Our trap collections continue to be above 100 moths per week as of August 15.

Lygus bugs are still causing damage to small bolls in some of our area cotton. Counts generally remain below 0.5 per foot of row.

The pyrethroids used for bollworm control are also very effective for Lygus control. Usually a boll larger than 1 inch in diameter is safe from Lygus damage, although stinkbugs may still be a problem. Conchuela and green stink bugs have been reported in area fields, but counts remain low at this time.

Fall armyworm infestations have been reported in Lubbock County, while only an occasional larvae has been observed in fields we are inspecting. Dr. Jim Leser has indicated that Karate and Capture are very effective for control of fall armyworm in cotton. Yellow striped armyworms have been very common this year in area cotton, but most damage has been confined to blooms.

SORGHUM

The Texas Department of Agriculture issued a crisis exemption for the use of bifenthrin (Capture 2EC) to control Banks grass mites on seed sorghum in 40 High Plains counties. Some seed sorghum female lines have been sensitive (foliage burn) to dimethoate and Comite which have been used for mite control in commercial sorghum. Potential mite resistance problems to Capture have been reported the past few years from counties north of Amarillo in corn. Historically we have been able to achieve higher levels of mite control in sorghum when compared to corn, which is probably a factor related to coverage. This is why dimethoate has been effectively used in sorghum and rarely used in corn as a stand alone treatment. For specifics on the use of Capture in seed production sorghum, contact your closest Extension Agent - IPM, Extension Entomologist, aerial applicator or Texas Department of Agriculture (website: www.agr.state.tx.us).

CORN

Southwestern corn borer red line eggs were found last week, but most eggs observed have been hatched or parasitized. Our plots at Halfway have had very high parasitism rates, which has made it difficult to screen insecticides.

Many fields are now very close to being ready for harvest. Moisture lines in kernel of 100% dent fields ranges from 25% to 100% down. Many fields are past the 50% down level. In general our corn crop looks much better than last year and I expect some very good yields. With the higher corn prices we may see good profits for this years crop.

*** UPCOMING EVENT ***

 

Greg Cronholm, Extension Agent - IPM,
122 East 6th, P.O. Box 680
Plainview, TX. 79073-0680
806-291-5273
Ento. Dept. Website: http://entowww.tamu.edu
Dist. 2 Website: http://lubbock.tamu.edu
E-Mail: g-cronholm@tamu.edu

---

Posted at this web site by:
texagnet Internet Services.