Cotton has settled into the "dog days" of summer, hot and dry. Many fields are blooming with most of the remaining fields to enter bloom in the next several days. The furthest advanced plants have some big bolls. Where moisture is adequate, cotton is making excellent progress and not headed toward early cutout like we saw last year. Furrow irrigated fields are getting "hot" and more dryland fields are moving into this category as the chance of rain continues to be a distant target. Early square sets were a little lower than we would have liked but plants have for the most part made up for the early environmental stress and insect losses and are retaining a high percentage of their fruit.

As fields of cotton reach into the fourth and fifth weeks of fruiting, there will be a tendency for squares in secondary and tertiary positions to be shed. Don't confuse this with insect damage. Plant bugs and fleahoppers can be found in most fields but the number of fields needing treatment thus far has been way below expectations. First summer generation boll weevils are appearing in high risk fields in areas outside active eradication programs. Punctured square counts have increased in a limited number of cases---some of these requiring treatment. The Texas Boll Weevil Eradication Foundation has thus far conducted a very successful program with trap catches reduced 96-99% below last year.

Caterpillar pest problems have been few this past week with only a limited number of fields in the Sudan area needing treatment for square-feeding beet armyworms. A few fields have been treated for bollworms, but again, this is the exception, not the rule. Natural enemy numbers have remained exceptionally high. Their activities in conjunction with our hot, dry conditions has contributed to high pest mortality levels. Cotton aphids remain below treatment levels thus far. Some concern has been expressed with our higher-than-usual numbers of whiteflies. Our whiteflies are the banded-winged species and not the devastating silverleaf whitefly of the LRGV, Arizona and California. No need to get excited about this potential pest yet.

New first position squares are produced about every 2.7 days (2.5-3.0 days). Pinhead-sized squares are 1/16^th inch in diameter and reach matchhead size in about 3-5 days and pencil eraser size (1/4^th inch) in another 3-5 days. Most squares that are shed are smaller than matchhead in size. Fleahoppers only damage pinhead-sized squares while plant bugs and stink bugs can damage larger squares. Once a plant has reached its carrying capacity of fruit, it will start aborting squares. These are invariably squares in the secondary and tertiary positions, not first position squares. If terminal squares are intact, and blasted squares only appear in the 2^nd and 3^rd positions, then insect damage should not be suspected.

If cotton comes under severe stress such as moisture or nitrogen stress, then physiological square shed could occur. Otherwise, most square shed prior to bloom should be insect related. There are, of course instances where we have observed square shed which can only be explained by environmental stress. Some varieties appear to be more susceptible to environmental stress and even insect damage than other varieties. But the bottom line is you should expect to hold on to most of your squares prior to bloom and even a couple of weeks into bloom.

Irrigated producers should be shooting for high square retention during the first 3-4 weeks of squaring, ending up with about 75-80% retention at this point. These early fruit are your guarantee against a late crop and plants with too much vegetative growth. A plant will only mature about 50-60% of all squares produced but shedding of fruit will mostly be as small bolls.

Most plant bug problem fields have been near alfalfa, peanuts or pastures. While potential problems with plant bugs can continue even past peak bloom, fleahopper problems are generally over by the end of the 4^th week of squaring. Once enough fruit are at hand to reach yield targets, fleahoppers should be looked upon as beneficial insects and no longer pests. Research has proven that this bug can be an effective predator.

The treatment criteria for this generation of weevils is far less aggressive than that used for emerging overwintered boll weevils. We can ill afford to use the earlier threshold for fear of eliminating beneficial insects and creating an outbreak of aphids, beet armyworms or bollworms. Prior to peak bloom, the treatment level is reached when 20% of the squares examined are punctured. If on a weekly scouting schedule and you hit 15% punctures, I wouldn't wait until next week to make a control decision.

Fields should be scouted by examining at least 100 squares across the entire field. These squares should be about 1/4 inch in diameter and not have any outward appearing symptoms of damage. Fallen squares or obviously yellow or flared squares should not be included. Early punctured squares will be mainly from feeding. These squares will have associated bright yellow pollen frass present. Once egg laying commences, these punctures will be generally on the lower 1/3^rd of the square.

If you find adult weevils during your field inspection they will often be "red" weevils and not the usual gray weevils observed earlier in traps. Newly emerged weevils do not take on this gray color until a few days later. The presence of red adult weevils in a field indicate that reproduction is taking place there. It will be about 4-8 days before these "new" weevils will begin to lay eggs. A female weevil can lay as many as 100 eggs during a 30 day stretch.

Several insecticides are available for weevil control. These include Guthion, ULV malathion, methyl parathion, Penncap M, and Vydate. If infestations are light and building slowly, you might consider using Thiodan or Phaser to preserve more of your "beneficials". These last two materials do not last long. A second application may be necessary five days after the first, regardless of insecticide used. Pyrethroids should only be considered if western tarnished plant bugs are in the mix. The threat of flaring aphids is not worth the risk.

Of course if you are in an active eradication zone you need not worry about boll weevil control. The Texas Boll Weevil Eradication Foundation is responsible for this. GRID trap catches remain pretty low although there have been some increases in a few locations. The Foundation was recording a trap catch reduction a week ago of 96.6% for the Northwest Plains Zone, 98.6% for the Permian Basin Zone and 99.4% for the Western High Plains Zone. Total accumulative acres treated across the three zones adds up to 243,275 acres. The three zones have a total of 2,048,292 program acres. The accumulative acres treated only adds up to 12% of all program acres.

If you must control BAW then consider using one of the big four, Tracer, Steward, Denim or Intrepid. I am kind of partial to Intrepid right now because of its longer residual activity and lower impact on natural enemies than the other three. Don't misunderstand me, the other three BAW materials have lower impact on "beneficials" than pyrethroids and other materials in our arsenal, but they still can have more of an impact than Intrepid.

Widespread aphid infestations held back by natural enemies. Aphid numbers continue to stay at levels we can all tolerate. Some fields have aphids on expanded leaves but most infestations remain in the terminal and on squares. You can thank natural enemies for the lack of economically damaging aphid infestations. If numbers per leaf do reach 50 or more per leaf and appear to still be in the increase mode, you will need to consider control. Bidrin or Centric are probably the best registered materials for aphid control. Furadan 4F is again available under a Section 18 for use this year. But this year you will be able to use this Furadan 4F immediately without prior documentation of control failures or resistance. You can thank the Texas Department of Agriculture for this worthwhile change.

Our species is the banded-winged whitefly (Trialeurodes abutilonea). This whitefly feeds much like our cotton aphid, causing similar damage. The difference is of course related to size. The small size of whiteflies means that it would take many more per leaf to cause comparable damage resulting from aphid feeding. No threshold has been established for this insect. I would expect that it would be above 100 per leaf at the very least. If control becomes necessary, Orthene or Address appear to be the materials of choice although I am sure there are others.

The reason this insect is more visible than aphids when walking a field is because adults more readily fly than do the winged aphids. Also, unlike adult aphids, all whitefly adults are winged. Immature whiteflies are flattened, oval nymphs, which attach themselves to the undersides of leaves. They appear scale-like, remaining quite stationary, sucking sap from the plant. They do not inject a toxin. The nymphal stage lasts about a week with the entire life cycle taking about two weeks.

Second generation southwestern corn borer adults are flying. Trap captures will peak late this week or early next week. European corn borer numbers are fairly low this year and flights will peak toward the end of next week. Transgenic Bt corn is protected from borers. Mites are not a problem yet, but the hot temperatures and reproductive stage corn make conditions ideal for an outbreak. Watch the mite populations, especially if the field is treated for borers or rootworm beetle adults. PP

Greenbugs and mites are in fields, but not at economically significant levels yet. Conchuela (stink) bugs and other stink bugs are showing up. The grey and red conchuela bugs are more abundant in some years, and it is news to no one that this has been one of those years. Stink bugs feed mainly on kernels, and cause most damage during kernel development. There are extensive economic threshold tables in our publication, "Managing Insect and Mite Pests of Texas Sorghum": http://insects.tamu.edu/extension/bulletins/b-1220.html#pfbugs. This might be a good time to highlight one of our new publications, "Field Guide to Pests and Beneficials in Texas Grain Sorghum", written by Stormy Sparks and John Norman. This publication has excellent photographs and short descriptions of pests and damage. It is available on the web: http://lubbock.tamu.edu/ipm/AgWeb/sorghum/insect/docs/FieldGuidePestsB6094.pdf or a paper copy can be ordered from Ag. Communications http://texaserc.tamu.edu/catalog/index.html. PP

Sunflower moths have been fairly heavy in some areas, requiring two insecticide applications. Some fields have significant numbers of stem weevil larvae in stems. This poses a risk of lodging later. The best course of action may be to harvest as early as possible and don't cut off the irrigation water too soon. Stem weevil damages the water and food transport system in the plant, and seed filling will be less efficient, especially if the plants are water stressed. PP

Sunflower moth follow-up. Previous issues of FOCUS have discussed the timing of spray applications to control the damaging sunflower (head) moth. In general, sunflower moth infestations can often be traced to having sprayed too late with initial sprays. We have said little about when to stop spraying for sunflower moth.

The sunflower moth is generally active and laying eggs only during the time when there is pollen on the head. Otherwise, without the access to pollen, sunflower moths are essentially considered sterile. Bloom does not always occur uniformly across a field, though that is a goal especially due to sunflower moth potential. Because there is a 5 to 7-day interval between sprays (if a second is needed), growers may recognize that when only a few heads remain in bloom it is not worth the cost of additional spraying. For example, a grower sprayed on Day 1 at 8% bloom and again at nearly full bloom about 6 days later. At that point percent bloom depends on the hybrid, but could be more than 90% after six days (this is considered fast!). In this scenario, an additional spray is often warranted because although 90% of the individual heads may be in bloom, active flowering may not have concluded on the interior of the head. The contribution toward yield from that portion of the head may be relatively small, but opportunistic infections that occur such as the Rhizopus fungus can affect otherwise healthy heads.

A final note about sunflower moth. As much of the South Plains sunflower crop is already past bloom and maturing; farmers, consultants, and scouts should not neglect to examine heads after bloom for evidence of larval infestation. You may observe larval webbing and frass (larval excretions) on the head. If infestations in the head have occurred, but a spraying program was followed, then growers have the opportunity to consider what might have gone wrong and how to address it in future years. In some regional fields as many as ten sunflower moth larvae have been observed per head, and Rhizopus head rot, in spite of the dry weather, has already set in. CT

Overview. The summer syndrome has set in over the last week, with highs consistently reaching the upper 90's and low 100's. Low temperatures have been in the upper 60's and lower 70's. The heat unit accumulation for the last several days has been averaging about 22, 25, and 25 per day for Halfway, Lubbock, and Lamesa, respectively. As a percentage of the long term average from May 1, the total heat unit accumulation is 9, 18, and 19 percent above normal, and the seasonal totals are now 1015, 1176, and 1286 for Halfway, Lubbock, and Lamesa, respectively. According to the PET Network data, reference ET has been averaging about 0.30-0.35 inches per day across the region for the last several days.

Large bolls can now be found in some late April and early May planted fields, while mid-May cotton will soon enter bloom stage. Some of the dryland fields with limited moisture and which made stands are now beginning to crash. However, some dryland fields, which received rainfall in late May or early June, are continuing to hold up remarkably well. We desperately need rainfall soon to save these latter fields and to reduce pumping expenses for irrigated fields. With the current forecast of no rainfall, high temperatures in the upper 90's and low temperatures in the 70's, it appears that will not likely occur.

Table 1. Mean (range) percent first position square retention data from large plot systems variety trials. 2001

Fusarium Wilt. I received a call from a crop consultant who reported significant stand losses in an irrigated field in Gaines County, west of Seagraves. Inspection of the field indicated that Fusarium wilt was the culprit. Although root knot nematode symptomology was observed, the wilt was responsible for the observed stand reduction. The field was planted in late April to the picker variety Stoneville 474. Dr. Terry Wheeler (Experiment Station plant pathologist) has observed Fusarium wilt in other Stoneville varieties (BXN 47 which has 474 as the recurrent parent) in this area before. A substantial portion of the half-circle is affected, and the producer notes that after each irrigation, more plants begin to die.

There is nothing that can be done to save the field, especially as the disease advances and infects most of the remaining plants. The best answer is to probably save the irrigation water for another crop. The best strategy is to plant a variety which has greater levels of Fusarium tolerance in this region. Dr. Wheeler notes that Fusarium oxysporum (the causal fungal organism of the wilt) has a survival stage that will last for many years. So rotation for one or two years out of cotton will not reduce his risk for Fusarium wilt appreciably in that field. Fusarium wilt is generally limited to sandy soils and is many times found in conjunction with root knot nematode infestation (Fusarium wilt photos - photo 1, photo 2, photo 3, photo 4, photo 5, photo 6, photo 7, photo 8, photo 9). RB

Yield potential has three distinct yield components. Yields can be tied to the degree of environmental stresses (or lack thereof), which may affect each component. These three yield components when yield potential is set are first growing point differentiation, then flowering, and finally grain fill.

At growing point differentiation (GPD), the plant switches from strictly vegetative growth to reproductive growth, even though you cannot see it without looking closely. The growing point is differentiating to develop a head with spikelets. Up until this time the growing point was producing new leaves. In most grain sorghum hybrids the GPD occurs about 30 to 35 days after emergence (about the 7 to 8 leaf stage). The growing point is now above the soil surface. From this time forward the potential number of spikelets and the number of kernels per spikelet will be determined. If conditions are very dry and irrigation water is available, watering just in advance of GPD is considered reasonable.

At flowering the actual number of seed is determined. As with any crop, flowering is a critical stage in sorghum development. Exceptionally hot, dry weather can curtail pollination, hence the actual number of seed may be limited. But because sorghum typically flowers over a period of about 4 to 9 days, one single hot day may not necessarily drive yield potential down.

Good grain fill increases grain size and weight. It is the last of the three primary components of how grain sorghum yield potential is determined.

Growers who are able to irrigate sorghum, however limited, should consider the importance of timing on irrigation in relation to the above physiological stages of development in order to optimize the potential return on irrigation expenses.

For further information regarding sorghum growth and development, the San Angelo Center has posted "How a Sorghum Plant Develops" at http://sanangelo.tamu.edu/agronomy/index.htm by Richard Vanderlip, Agronomy, Kansas State Univ. Also, Brent Bean and Carl Patrick, TAEX, Amarillo, have summarized in "Sorghum Development and Key Growth Stages," which is available at . http://lubbock.tamu.edu. CT

"Warm and sunny" sounds better than "hot and dry". Either way, reference crop evapotranspiration water demand has been high, and the short term forecast is not promising precipitation. Reference crop ET for this week at Lubbock was approximately 0.34 inches per day; historical long-term average for this time of year is 0.29 inches per day.

Corn and early planted sorghum are in or approaching their peak water use stages (tassel through milk stages for corn; boot through flower stages for sorghum). Cotton and peanuts (hopefully) are still advancing toward their peak water use stages. To state the obvious, this would be a good time for some rain.

A side note: I occasionally receive calls from consulting firms and modeling groups who plan to use ET data to predict water pumping, groundwater recharge, and/or energy usage. I am pleased that our data are available to the public for a range of applications, and that these groups find the information helpful. However, I advise exercise of caution in making assumptions necessary for modeling efforts, as reference crop water demand is not necessarily the same as actual crop water demand (Please see the table below as an illustration of the effects of crop type and growth stage). Also note that deficit irrigation is a common practice in the Southern High Plains. Under deficit irrigation, only a fraction of the crop's water demand is actually provided through irrigation. For example, water demand for cotton at first bloom stage was estimated to be approximately one inch last week. If 0.75 inch of irrigation was applied, only 75% of the crop water demand was supplied. Irrigation management may range from dryland (no irrigation) to full irrigation (all the crop's water demand is met). Most irrigated production in this region falls somewhere between dryland and full irrigation. Of course, drought tolerant crops are selected in part because they perform well under deficit irrigation conditions. Several years of research at the AGCARES research facility and other locations has indicated that cotton performed well when it was irrigated at 75% ET replacement, particularly when efficient irrigation application practices were used. Certainly our ET data are better than "no data", but the application of the information may be a little more complicated than it seems at first glance. Weather is only one of many uncontrollable factors that enter crop management decisions. DP

Table 2. Crop water demand estimates (inches per week) for the week of July 5-11, 2001.

* Reference crop for these ET estimates is a cool season grass. Crop-specific ET estimates are affected by growth stage; ranges of values are presented for the reader's convenience and to accommodate the ranges of crop growth stages in the field.