Texas Agricultural Extension Service

Volume XXVII No. 14 June 1, 2001 GENERAL SITUATION: Another hot and dry week, mostly. Some rain fell in isolated spots in eastern and southern Cameron county on Thursday, May 31 and some rain is predicted for spots in western Cameron and eastern Hidalgo county today, June 1. Rainfall amounts on Thursday ranged from 1/10th to nearly 3 inches based on doppler reports from the weather service. Again, spots only. All of the crops are suffering from a lack of moisture. More fields of cotton were blooming near the top of the plants, some sorghum fields appeared to be withering without much chance of yield and corn appears to be headed to a lower yield, despite irrigation. Some fields have a chance for a decent yield if adequate rain comes within the next week or so. Insect activity was increasing, particularly in cotton. Continued Dry Weather Hurts Cotton Open bolls of cotton were not observed or reported this week, but likely some are present in a few fields due to very dry conditions. Some fields of irrigated cotton were not growing well despite irrigation, but most of the irrigated and some of the dryland fields appeared to be in pretty good shape overall. Most cotton, dryland and irrigated alike, performs better when there is some rain on a regular basis. Even if supplemental irrigation water is used, fields will grow and generally yield better when rain is the principal source of moisture rather than irrigation water. Small boll shedding was again observed, but in higher numbers of lost fruit over a larger number of fields. Boll shedding will continue even if fields are irrigated or it rains. The amount of boll shedding is a function of the plant's ability to have moisture in the right amounts at the right time. If the plants become too dry over a given period of time, then bolls which are going to be shed will have been determined by the plant's ability to hold the fruit it can mature with the moisture (and nutrients) it has available. Boll shedding likely will be faster if it gets a big shot of water, either rain or irrigation, because the plant will start to grow and the fruit which was going to be lost anyway, will be dropped at a faster rate than without rain. Hopefully, we can receive substantial rain and stop fruit loss which has not yet been determined by the plants. Boll Weevil Punctures Going Up Boll weevils continued to make inroads by infesting some previously un-infested fields. Previously infested fields had higher counts of weevil punctured squares this week. Boll weevil punctured squares were not high, but were found in a range from 0 to 18 per 100 plants in fields scouted this week. Adult weevils were not easily found except in the few spots where punctured square counts were the highest. Hot and dry weather was taking its toll on some weevils and the crop. That's because the hot and dry weather conditions act like a two-edged sword in cotton. Some dead boll weevil grubs in squares on the ground were found this week due to the heat. Weevil grubs are subject to heat death if the canopy of the cotton field has not closed over, especially in years when hot and dry weather prevails. While there may be slightly fewer

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weevils were surviving the current hot conditions, most appeared to be doing just fine if the squares in which the grubs resided found their way to the middle of the cotton drill and got nearly all day shade.

Another survival tactic that works for boll weevils occurs in irrigated fields. The irrigation water cools the soil surface and a larger proportion of the grubs in squares have a chance to live. Irrigation water also will help make a larger plant canopy and thus provide more shade for the grubs. Rain will also increase weevil survival, but most everyone would welcome those extra weevils to get the needed rain at this point in time.

The other edge of the dry weather sword is reduced yield. The hot and dry weather keeps the yield potential of cotton lower and thus reduces further any chance of a profit from the cotton crop.

Boll weevil pheromone trap captures were lower again this week (See attached graphs). They should stay that way for another week or two, as long as cotton remains in a good growing and fruiting state. When the cotton crop begins to dry down because of the dry weather and physical maturity, weevils will begin to move around to find more suitable fields.

Then, trap numbers will increase. Without some substantial rain and soon, weevil trap numbers could start to go higher shortly.

Pay Attention to Spider Mites

Spider mite infestations continued to be reported this week. No reports of serious damage were received related to spider mites, but the threat was apparent in some fields based on increasing mite infestations in some fields. Both minute pirate bugs and lacewing larvae were observed feeding on spider mites in some fields this week, but mite numbers were increasing in some cases despite the beneficial activity. Growers should monitor spider mites very closely.

Beet Armyworm Moth Counts Higher

Beet armyworm (BAW) activity was not high in fields, but moth captures in pheromone traps were up this week. No reports of beet armyworms feeding in cotton were received this week. A few plants with damaged leaves which were similar to BAW feeding were detected, but no larvae were observed. Moth trap counts were highest in our two traps southwest of Lyford, south of 491, east of highway 77. Other trap sites showed increased captures this week also.

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Beet Armyworm Trap Records

Cotton Aphids Down Even More

Cotton aphid infestations were down, but some aphids were found at near threshold levels this week. Overall, aphids were controlled by natural enemies, insecticides or both in some cases.

Bollworms Still Light

Bollworm/tobacco budworm infestations again were low this week. Worm counts ranged from 0 to 5 per 100 plants and damaged square counts from 0 to 6 per 100 plants.

Sorghum Midge Continue Increase

Sorghum midge were increasing in blooming sorghum fields this week. Counts were less than 2 per head in fields scouted this week. Look for increases from this point forward. Late planted sorghum needs at least twice weekly monitoring from this point onward in order to determine midge levels and crop susceptibility to damage.

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