Texas Agricultural Extension Service

Volume XXVII No. 13 May 25, 2001 GENERAL SITUATION: Rains, some very heavy, fell in the western end of the LRGV fell this week. Most of the grain sorghum, cotton and corn country got very little of the rain. Amounts ranged from a reported 6+ inches to a light sprinkle. The area's crops need some rain and fast, especially cotton, if it is going to make much of a crop with the fruit load it currently has on the plants. Insect activity increased in cotton this week. Cotton Cooking Many dryland cotton fields were beginning to shed a few small bolls this week. The fruit load on much of the dryland and irrigated cotton has been heavy considering the amount of water the LRGV has received in the last few months. But, the shedding is indicative of plants coming under increasing stress, particularly from a lack of moisture. Many fields, some irrigated and many dryland were blooming at the 6th to 4th node above their white blooms, some at the top of the plants. A few more days to a week without rain will push those fields to the point of cutout. The normal cutout time in the Valley is near the end of June for the early planted fields. Earlier than normal cutout will mean a further reduced yield potential since cutout usually is "the end of the line" for cotton field in that condition. We need rain quickly. Weevils Making Fast Moves Boll weevil punctured square counts seemed to have rocketed in a few fields over this past weekend and continued into this week. Punctured square counts went from 1 or 2 per 100 plants late last week to well into the 20-30 per 100 plants range in a few fields this week. Many fields had weevil punctures showing up this week. Many weevil grubs and some pupae in squares on the ground were detected in some fields in which puncture squares were noticeable this week. Weevils Trapped Continues Decline Boll weevils caught in our trap lines showed declines again this week (See attached weevil trap graphs). We generally expect the weevil numbers to decline and stay that way until about mid-June or so because pheromone traps cannot compete with vigorous growing and fruiting cotton plants for weevils' attention. Aphid Populations Unsettled Cotton aphid populations remained low in most fields, but increased some in others this week. If cotton is in the blooming stage of growth, the threshold for treatment is much lower than in pre-blooming cotton. Carefully examine all fields with aphids to determine the growth stage of the plant and the number of aphids present.

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PEST CAST continued

If the cotton is blooming and there are 50 per leaf or greater and no or few beneficials are present then a treatment may be necessary to control the aphids. A few aphids on the cotton will not hurt the yield, even if some of the terminal leaves appear to be wilting. If beneficials are present and in moderate to high numbers, the aphids likely will be doomed. Many fields with moderate to heavy aphid populations this week had very heavy beneficial numbers working the aphids. Fields which late last week had very heavy aphids had considerably lower aphid numbers this week, again due to beneficial insects or spraying in some cases, just like we reported in last week's Pest Cast.

Many of the beneficials were lady beetles, scymnus lady beetle larvae (they are the white colored mealy bug-looking critters found in and around aphid colonies) and large numbers of aphid mummies, indicating large numbers of parasites attacking the aphids.

Aphids can be reduced within a few days from very large to very small numbers by beneficial insects if given the chance. Keep scouting to make certain that the beneficials are not doing their job before treating.

Spider Mites in the Race

Spider mites (two spotted mites, also often referred to as red mites or red spider) were increasing to treatable levels in some fields this week. Spider mites, which feed on the underside of leaves, often leave a characteristic light colored speckling on the upper surface of the infested leaves of cotton. The speckling is usually located along the main veins of leaves. The mites usually feed on the underside of leaves and it is only when populations become very large that they tend to spread to other plant parts including the upper part of the leaves, square bracts and terminals. Mites often form webbing on the underside of the leaves when their populations become large.

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Spraying for Spider Mites

Treatment for mites may be justified when noticeable leaf damage occurs. Spot spraying for mites is often adequate to control the population unless the problem is field wide. Thorough coverage of the plant canopy with the miticide is critical to achieve good mite control. Simply spraying over the top of the canopy will not do a good job of mite control, unless the mites were so low that control was not necessary in the first place. Remember, the mites live under the leaf and unless the miticide makes contact directly with the mites (the chemical hits the mites or the mites crawl through it), control will be minimal at best.

Square Borers Lite

Cotton square borers were noted in a few fields, but in very low numbers this week. Damaged squares by cotton square borers appears to be identical to bollworm or tobacco budworm, except that the hole left by the borer is perfectly round and the borer leaves no frass (excrement) in or around the damaged square. The adult of the cotton square borer is a butterfly as opposed to the adults of bollworm and tobacco budworms which are moths. The square borer butterfly is a small ( about 1.25 to1.5 inch wing span), grey colored butterfly with small red spots on the wings. Square borers usually are less noticeable in cotton fields once the really hot months of June through August come around. We have had reports that cotton square borers were the main pest of concern in some fields in the coastal bend area north of the LRGV this week.

Bollworms Normal

Bollworm/budworms were very light this week. Worm counts ranged from 0 to 3 per 100 plants based on reports received this week. Egg counts were not reported. Damaged squares ranged from 1 to 5 per 100 plants.

Beet Armyworms Quiet

Beet armyworms (BAW) were scattered in low numbers (less than one larvae per field) as they were last week in cotton. BAW moths caught in pheromone traps

were slightly higher at all trap sites this week compared to last week, but still in low numbers.

Beet Armyworm Trap Records

Cotton Fleahoppers Still Around

We have not mentioned cotton fleahoppers very much of late since the cotton crop is so far advanced that fleas likely would not cause much if any damage. However, fleahoppers were seen in large numbers around wooly croton (dove weed) again this week. Large numbers of adult fleahoppers were observed where the croton was in the highest concentrations. A few fields of cotton were just beginning to square this week and are susceptible to damage by the fleahoppers. Late cotton is always a challenge to produce in the LRGV, and fleahoppers are just one of many insect and weather related problems for late cotton. And if fleahoppers do serious damage to the later planted fields, they will become even later maturing in order to make up for the earlier lost squares. Watch those fields carefully.

Greenbugs

Greenbugs continued to be found in many fields this week, but at slightly lower numbers due to beneficial insects and the fungus. So far, the numbers have not been overwhelming in most fields, but aphids and damage continue to be present. Scattered fields had obvious greenbug damage symptoms with red colored leaves appearing throughout the fields. All fields therefore, need to be monitored.

Midge Increasing

More sorghum midge were seen in a few fields this week. Nothing to write home about, but worth watching since midge numbers likely will only go higher in the next few days to weeks.

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