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Vol. 30, No. 7

COTTON

Scattered showers Friday through Sunday morning helped relieve stress for some of our cotton. Rainfall reports ranged from none to 0.8". This past week many cotton fields were showing signs of stress by wilting in the hot afternoon heat. So far little square shed has been observed in irrigated fields due to stress. Dryland fields are now bloomed out the top and if any significant rain occurs this week, they may have some yield potential.

Cotton bollworm activity remains spotty, with populations ranging from 0 to 12,000 per acre. New egg lays were difficult to find this past week and were mostly observed in the well water fields. Trap collections of cotton bollworms/corn earworms had generally declined through last Thursday. Many corn earworms in corn and sorghum have left the plant to pupate in the soil, based on observations over the past week. Looking at the distribution of larval sizes in corn we should have a longer than normal flight period. Based on these observations we may see some early activity (egg lays) as early as August 5. Activity is expected to increase through mid-August and may not conclude until around August 26.

Cotton aphids remain light in most area cotton fields, but a few have exceeded 100 per leaf. The fields with 50 to 100 aphids per leaf have had good ladybeetle activity and it is not unusual to find some leaves with very

few aphids even though honeydew and cast "skins" indicate a heavy population had been present . Furadan has received a section 18 again this year for aphid control in cotton, but it still has a 14 day re-entry period. Centric and Intruder are two newer materials used for aphid control. Centric is labeled a 2 ounces per acre; while Intruder is labeled at 0.6 to 1.1 oz/a. Other products used for control or suppression are Bidrin, Provado and Trimax. Leverage is a product that has a combination of a pyrethroid for bollworm control and Provado for aphid control.

Lygus populations have tended to remain stable, although some fields have had an increase in nymphs. Overall, Lygus populations remain light.

Treatment for boll weevils continues in cotton for our zone with 21,000 acres treated for the week ending on July 21. With such a small amount of acres treated on a weekly basis, we have not had any widespread secondary pest outbreaks such as cotton aphid or beet armyworm. We have tended to see higher aphid populations in fields which have been treated for weevils; so watch these fields closely. Also, fields treated recently for bollworms should be monitored for aphid increases.

CORN

Southwestern corn borer egg lays remain lighter than the previous few years. Trap collections are much lower than normal at this time.

Banks grass mites are on the increase in many fields. The higher populations have been found in drought stressed areas of the field. Overall, corn continues to look very good and most fields range from soft dough to hard dough. A few fields are entering the dent stage.

Corn earworms and fall armyworm infestations have declined as larvae have moved to the soil to pupate.

SORGHUM

Sorghum ranges from boot to bloom to seed fill. Fields that are still blooming should be scouted daily for the presence of sorghum midge. Midge usually do not reach damaging levels in our area until after August 1. The best time to scout for this pest is from noon to 3:00 p.m.. If the night time temperatures are unusually warm and mid-80 temperatures are reached before lunch then 10:30 to 11:30 a.m. may be an acceptable time to start. Scouting late into the afternoon or early evening may not be as effective since a significant amount of the midge population may have died due to completion of oviposition. The following table may help you to determine a treatment threshold for your field.

Economic injury levels based on number of adult
sorghum midges per flowering grain head of a
susceptible sorghum hybrid.

Control      Crop market value ($) per acre
cost ($)  ___________________________________________
per acre  100  125  150  175  200  225  250  275  300
_____________________________________________________
                 Number of headworms
6         2.4  2.0  1.6  1.3  1.2  1.1  0.9  0.8  0.8
8         3.0  2.5  2.2  1.8  1.6  1.4  1.2  1.1  1.1
10        3.5  3.0  2.6  2.2  1.9  1.7  1.5  1.4  1.3
12        3.9  3.5  3.1  2.7  2.3  2.0  1.8  1.6  1.4