Volume XXVII No. 13 June 17, 2002 GENERAL SITUATION: Scattered, light showers came in hit and miss fashion (mostly mist), around the LRGV this week. Otherwise, hot and dry conditions continued to pressure cotton and grain fields. Maturity in most fields was evident by the number of medium to large bolls being observed in irrigated fields and the number of dryland fields which slid further into the negative yield category. Insect activity increased. Boll Weevils On the Move Boll weevils made more moves into cotton this week. Punctured square counts began to reach levels requiring insecticide control in many more fields. Punctured square counts ranged from 0 to 15 per 100 plants. It was easier to find punctured squares laying on the ground, especially along field margins this week than last. New weevils feeding on squares also were easier to find this week than last. The "boll weevil showers" of last week appeared to have "rained" new weevils last week based on the punctured square counts this week. Bollworm Numbers low Bollworm egg and worm counts were reported to be lower this week than last week's counts. Egg counts ranged from 0 to 2 per 100 plants and worm counts from 0 to 2 also. The egg laying and worm counts could be higher in individual fields depending on when the moths that were laying eggs emerged and mated. Carefully check each field to make certain of worm and weevil punctures before applying any insecticides. Cotton Fleahoppers Heavy in a few Fields Cotton fleahopper counts were higher in a few fields than last week. Fleahopper numbers ranged from 0 to 80 per 100 plants. Damage by fleahoppers at this stage on mature cotton will be negligible. However, very young cotton needs to be monitored frequently to determine if fleahoppers are causing enough damage to warrant treatment. Aphids Heavy Some Places Aphids were causing some concerns in a few area fields this week. One report from fields in the Brownsville area indicated aphids were heavy in some fields despite repeated insecticide applications. Repeated insecticide applications for other pests could cause an aphid resurgence in other area fields and should be monitored often. Special for Pest Cast From Charles Stichler, Extension Agronomist Before we know it, combines will be moving into fields to harvest grain sorghum. However, there will be problems in many fields due to uneven growth and development. Combining grain that has delayed maturity and "suckers" can cause high moisture grain, poor threshing and delayed harvest. There are some possible solutions to some of the problems, but growers need to carefully consider their options.

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The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas Cooperating.

PEST CAST continued

1. When grain reaches approximately 30% moisture it is physiologically mature. What does that mean? Physiological maturity means the grain seed has been sealed off from the "mother" plant and is no longer getting nutrients and moisture. The grain is simply drying down and will no longer increase in weight. By taking samples from the majority of the field where grain is harvestable, the moisture of the majority of the acreage can be estimated. When it falls below 30%, glyphosate can be sprayed over the field to kill the sorghum. BE PREPARED TO HARVEST IN 7 - 10 DAYS. Glyphosate will kill the sorghum and it will dry out rapidly. Glyphosate will also kill any weeds or Johnsongrass in the field.
2. Sodium chlorate is another product that can be sprayed over sorghum to dry the plants out. Sodium chlorate is a desiccant only. It will not kill the plants, and they will eventually regrow.

ALWAYS READ AND FOLLOW LABEL DIRECTIONS WHEN APPLYING CHEMICALS.

Charles Stichler, Extension Agronomist, Uvalde

Watch Those Midge

Sorghum midge continued to be found this week. Counts ranged from 0 to 1 per head in blooming sorghum. Most sorghum appeared to be escaping damaging midge infestations for the time being. However, midge could be in large numbers in some fields and across the turn row at or near zero. Keep checking blooming sorghum.

Rice Stink Bugs in Sorghum

We have had some reports of rice stink bugs present in very low numbers in some sorghum fields. Generally, rice stink bugs are not a serious pest of sorghum in the LRGV. However, because no two years are alike, we felt it was important to provide everyone with some information about rice stink bugs that may not be commonly known.

Rice Stink Bug, Oebalus pugnax (Fabricius), adults are straw-colored, shield-shaped and1/2 inch long. The adult has forward projecting points on each shoulder. Females deposit 10-50 light green, short, cylinder-shaped eggs in a two-row cluster. Egg-hatch after about 5 days. Nymphs require 15-28 days to become adults. Rice stink bugs unlike regular or southern green stink bugs, have sharp point shoulders and have a pale green body with light tan wings. They generally are about ½ to 3/4 inch in length and are most often found when sorghum is in the milk to soft dough stage of head maturity. (The previous information taken from Texas Cooperative Extension Publication Field Guide to Pest & Beneficials in Texas Grain Sorghum, B-6094.)

Several species of true bugs, primarily stink bugs, may move from alternate host plants into sorghum in relatively large numbers during grain development. Bugs infesting sorghum in Texas include the rice stink bug, southern green stink bug, conchuela stink bug, brown stink bug, red shouldered stink bug, leaf footed bug and false chinch bug. Panicle-feeding bugs feed mainly on seeds and to a lesser extent on other panicle parts and may cause economic damage. Extent of damage depends on the number of bugs per panicle, duration of infestation and stage of grain development when infestation occurs. Bugs cause more damage early during grain development and less damage as grain develops to the hard dough stage. Both nymphs and adults may cause damage, reducing grain weight, quality and seed germination. Panicle-feeding bugs tend to congregate in clumps within a field.

The number of bugs per panicle which will reduce grain yield varies depending on the bug species and stage of grain development when infestation occurs.

There is currently no satisfactory technique for estimating the total number of panicle-feeding bugs per plant; however as these insect pests tend to congregate in the sorghum head, an estimate of the average number of bugs per panicle should provide a good indication of the need for treatment. The beat-bucket technique can be used to estimate the average number of bugs per head. Sorghum panicles should be shaken vigorously into a 5 gallon. Adult stink bugs can then be more easily seen and counted in the bucket. The scout should be alert for adult stink bugs flying from the sampled plant or from the bucket and look for bugs on plant leaves and weeds within the field to maintain an accurate estimate of the total number of bugs per sorghum plant. At least 30 plants from the whole field should be inspected to ensure reasonable reliability of sample results. Fields larger than 80 acres should be divided into portions no larger than 80 acres.

To determine the profitability of controlling an infestation of rice, southern green or conchuela stink bugs or leaf-footed bugs, calculate the per acre control cost (insecticide and application) and the expected per acre market value of the grain (yield x price). Next, determine the approximate grain development stage when the infestation occurred. If the estimated stage of development is hard dough and the infestation level per panicle is 16 bugs or fewer, do not control bugs. For bug infestations beginning at the milk or soft dough stages, consult the economic injury level tables. Economic injury levels for infestation (rice stink bugs per panicle) at which control is justified are indicated for various control costs and market value.

PEST CAST continued

Per plant economic injury level for an infestation of rice stink bugs during the anthesis stage of grain development.

Per plant economic injury level for an infestation of rice stink bugs beginning at the milk stage of grain development.

Per plant economic injury level for an infestation of rice stink bugs beginning at the soft dough stage of grain development.

(The previous information taken from Texas Cooperative Extension publication B-1220, Managing Insect And Mite Pests of Texas Sorghum. )

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