Record high temperatures and dry conditions have stressed the irrigation capabilities of many cotton growers. As a consequence, numerous fields are approaching early cutout with a limited blooming period. Our dryland crop is finally reaching its limits and has entered a terminal downward spiral. Fields with adequate irrigation capabilities have large boll loads and are set for exceptional yields.

The main insect concern this week is for the increasing infestations of banded-winged whiteflies present in many but not all fields. This issue of FOCUS provides extensive coverage of this pest. Bollworm activity is increasing with a few more fields reaching treatment levels. Growers should expect more problem fields to develop over the next 7-10 days in spite of all the help we are getting from the abundant predacious insects and spiders. A few fields to the northeast are reportedly having problems with beet armyworms but for the most part we are relatively clean of this pest. Plant bug infestation levels continue to increase and producers are warned not to let this pest slip in and steal your last squares, flowers and bolls. Boll weevils remain at very low levels with activity relatively unchanged from last week.

Spider mites, primarily Banks grass mites, are responding to our hot, dry conditions and reaching damaging levels in many corn fields. Most of the current insecticide recommendations are failing to achieve adequate control. Both European and southwestern corn borer moth flights are tapering off but borer larval activity is on the rise in corn.

Producers are warned to watch for increased corn earworm activity in both peanuts and sorghum. JFL

Cutout is imminent for many cotton fields. Hot, dry conditions have continued across the west Texas area for yet another week, with spotty rain showers providing very little relief. The forecast for the next several days is for highs to move out of the triple digit area and back down into the high 90's. Nighttime lows remain in the low to middle 70's. These conditions have really pushed cotton along. Where moisture is adequate, cotton is taking advantage of these high temperatures and setting an excellent crop through an extended blooming period. Where moisture is short, plants are often reaching cutout a week to ten days after they begin to bloom.

The dryland crop has held up as well as could be expected under these hot, dry conditions but has begun to "crash" in many fields. Because of this early cutout in many fields, there will be opportunities to terminate some fields as early as some time in August. Once cutout occurs (Nodes Above White Flower = 4 or less) another 850-950 heat units is all that is necessary to set the crop up for a harvest aid application. At the current rate of heat unit accumulation (25-29 HU per day) this could occur in 29 to 38 days from cutout. The weevil threat would be over in 12-14 days and the threat from fruit feeding caterpillars would be over in 18-22 days. This would mean that for a field at cutout today, boll weevil worries would be over as early as August 8, worm problems over as early as August 14 and a harvest aid could be applied by August 25th. For some folks, the season is rapidly coming to a close.

Infestations in problem fields have numbers of adults ranging up to over 50 per leaf with nymphal numbers at lower levels of 2-20 per leaf. Infestations are generally not uniformly distributed across the field nor up and down the plant. Usually there are very few whiteflies on the lower third of the plant. These higher numbers are producing visible honeydew but not yet at levels that would be seen with an infestation of cotton aphids at threshold levels of 50 or more aphids per leaf. But, in spite of the yeoman service provided by predacious insects, whitefly numbers are increasing both through reproduction and movement of adults into fields from adjacent alternate hosts.

The typical questions we are getting (and my attempt at answers) are as follows:

What are the hosts for the banded-wing whitefly? The host range for this species is not as great as the silverleaf whitefly but nonetheless quite extensive. We are noticing large numbers of adults in sunflower but few nymphs at this time. This could be an important source for infestations moving into cotton and for re-infestation if a cotton field is treated. Several weeds in the Solenaceae and Malvaceae plant families could serve as hosts. These weeds would include silverleaf nightshade, ground cherry, black and hairy nightshade; venice mallow, alkali mallow/sida and velvetleaf.

What kind of damage can I expect from whiteflies? Much like aphids, whiteflies extract sap from plants, pulling out nitrogen, carbohydrates and water. The excess sugars and water are excreted onto the lower leaves as honeydew. Under humid conditions, this honeydew could provide a substrate for the growth of a sooty mold fungus, which could shade the infected leaf and reduce photosynthesis. This is most unlikely for a dry area such as ours. The main problem would come from excessive sap extraction and the subsequent reduction in boll size and weight. This would lead to a yield reduction.

Another, more serious problem that could develop would be honeydew deposits on open cotton. We've worried about this with cotton aphids before but whitefly honeydew is much stickier than aphid honeydew because of the trehalulose sugar present. This is one of the "stickiest" sugars. Hopefully this problem will be over before much cotton opens or we get a general rain across the area that will not only wash the honeydew problem away but also the whitefly problem. For more information on sticky cotton you can view the publication, "Sticky Cotton Sources & Solutions".

What about help from beneficial insects? There is no doubt in my mind that we are getting a lot of control help out of our abundant beneficial insects. But can they hold the line against an insect that has such a high reproductive rate? In fields with lots of whiteflies we are noticing increased numbers of minute pirate bugs. This is an excellent predator. We have also observed western flower thrips feeding on the immature stages of the whitefly. This thrips species is known to feed voraciously on spider mites. We can now add whiteflies to the list. We have also observed more than one species of wasp in relation to these whitefly infestations. I don't off hand know which parasitic wasps these are.

The Lower Rio Grande Valley guide recommends Phaser or Thiodan at 1.33 or 1.66 qts. respectively, for adult silverleaf whitefly control. They also recommend either Capture at 5.2 oz or Danitol at 4.2 oz per acre in combination with acephate (Orthene or Address) at 0.5 lb. active ingredient per acre for a combined adult and immature silverleaf whitefly control.

Arkansas suggests Capture at 3.9-6.4 oz per acre, Monitor at 16-32 oz per acre or Danitol at 8-16 oz plus 0.5 lb. active ingredient per acre.

Based on discussions with Arizona, I would not expect Provado to be a great material and therefore I would not be real enthusiastic about Leverage either. Thiodan or Phaser would be good adulticides but may not handle the immatures. I'm real curious about Centric and would expect that it would be a good material. The label has one rate, 3.0 oz per acre, and cautions that two applications may be necessary. I would also expect that several pyrethroids in combination with 0.5 lbs. active ingredient of acephate would handle adults and nymphs of the banded-winged whitefly. These pyrethroids might include: Asana, Baythroid, Capture, Danitol, Karate and Orthene. Other pyrethroids might work but I have no data available to me on these at this time. Extension IPM Agents Brant Baugh and Scott Russell initiated a whitefly control trial on Thursday on a field near Idalou scouted by consultant Nathan King. This is a quickie test and includes only Thiodan, Karate Z + Orthene, Centric and an untreated check. A 4-day post count will be made on Monday.

A few hot spots for beet armyworms have popped up. Numbers of beet armyworms in High Plains cotton fields remain very low for the most part. I did receive a disturbing report of a field off the Caprock northeast of here that averaged 38,000 "beets" per acre. Heat and numerous beneficial insects have helped keep troubles with this pest at a minimum. Trap catches are relatively unchanged from last week in the three active High Plains boll weevil eradication zones. Both the Western (WHP) (32 moths/trap-week) and Permian Basin (PB) (12 moths per trap-week) counts are much lower than last year (172 and 83 respectively) while the Northwest zone (NWP) (199 per trap-week) catches are running higher than last year (122) for this time of year. Still, trap catches are well below the levels we saw in June (over 300 in the NWP zone).

Producers that have failed cotton and have either left the field fallow or planted to another crop are cautioned to make sure there are no viable cotton plants left. If so, the Texas Boll Weevil Eradication Foundation will still have to trap the field, spray the field and assess you for the field.

Aphid infestations still not a problem. Luckily, aphids remain on hold in most fields with a few notable exceptions. With a potential bollworm problem around the corner, this could change with the expected increase in the use of pyrethroids. So far this pest is providing a nice source of food for many beneficial insects.

Natural enemies are finding a target rich environment. What more can I say? Large numbers of predacious insects and spiders continue to develop in most area fields. Low insecticide use by producers and the Foundation plus an abundant food supply have resulted in a very nice situation for growers. If we can continue to hold on to these insects and spiders then a number of fields will escape the season without the need of our assistance through supplemental insecticidal control. JFL

Spider mite infestations are getting worse. This is not a surprise to anyone. Mites are nearing the ear leaf in some fields. Things are worse north of I-40. Dr. Robert Bowling (Extension IPM Agent for Moore County) has reported severe control problems from Dumas to Dalhart. Growers there are trying everything in hopes of finding something that works. Robert said that the best job so far was a mixture of 2 pints Furadan + 1 pint Dimethoate + 2 pints of cottonseed oil applied with 5 gallons of water per acre. The cottonseed oil is not an insecticide, but it helps get more of the insecticide spray down in the canopy.

What happened to Capture? First, recall our advice against spraying for rootworm adults. Even if the mites were not at all resistant, but survived the rootworm adult application through one of several possible means, they would then be free to reproduce unchecked by beneficial insects and predatory mites. If a pyrethroid was used for rootworm adults, then the mites present were likely exposed to the pyrethroid. Spider mites resist pyrethroids through the mechanism known as target site insensitivity, which results from an alteration in the molecule against which the insecticide acts. If some mites in the field had some resistance, then some would have survived the rootworm adult application and continued to multiply, again unchecked by biological control. (Aside: early use of organophosphates would allow mites to crank up the mixed function oxidase (MFO) detoxification systems they use against organophosphates.) It is too soon to talk about tolerance or true resistance to Capture, especially since no one has run the laboratory tests that are required.

Secondly, Capture does not work as well in the heat as it does when it is cooler. And, stressed corn helps the mites become more tolerant of insecticides ahead of the actual application.

Third, while Banks grass mite is the most numerous species now, twospotted spider mites may also be present in many fields. A Capture application may have cleaned up most of the Banks grass mite problem, but left the twospotted mites relatively intact (suppression only). The hot and dry weather then promoted rapid increases in mites, and we ended up where we are today. This is why it is imperative to identify the mite species before choosing insecticides. Much of this is conjecture and hand waving, we do not really know what is happening. All I can say for sure right now is that Capture does not seem to be working well against Banks grass mites north of I-40, but reports from other areas suggest it is working fine.

Suggested insecticides in our new corn guide (unpublished) for Banks grass mite control will include Capture, Furadan + Dimethoate, Dimethoate, Comite II, and sulfur. The suggested arsenal for twospotted spider mites is smaller: Furadan + Dimethoate, Comite II, and sulfur.

According to previous work by Dr. Tom Archer and Eddie Bynum at the Lubbock Research and Extension Center, there may be some other options if things get really bad. A true synergistic mixture would be dimethoate + Capture + PBO (piperonyl butoxide). Growers could also try dimethoate + Capture + Furadan. It is essential to use at least 5 gallons of water per acre in aerial application, and more is better. Good coverage is a must.

We have not come to this point yet in Extension District 2, and hopefully we will not do so. Tolerance and resistance start out as local problems, and we do not spray adult rootworms as readily as is done north of I-40. Just because Capture and other insecticides are having problems north of I-40 does not necessarily mean we will have the same problems here. I would appreciate reports of control failures in our area counties.

Southwestern and European corn borer flights are tapering off. "Europeans" are at the tail end of their flight and "southwesterns" are somewhere near 65% done. If a treatment is justified, think about adding a miticide to the spray tank. PP

I lumped these two crops together because the corn earworm (one of the insects in the sorghum headworm complex) flight is beginning. Greg Cronholm and I trapped moths Wednesday night and found several very young and healthy earworm adults. Populations will pick up from here, so scout for eggs and small larvae. The hot and dry wind will help kill eggs, so it might pay to base treatments on small larvae. At a minimum, don't assume all the eggs will hatch. Dry, shriveled eggs are dead and round eggs are most likely still viable. I am not going to go into thresholds in this issue, in part because water is more important right now. PP

Karnal bunt is a fungal disease of wheat that has been common to India, Syria, Lebanon, Iraq and Turkey. In 1996 it was found in a sample of durum wheat seed in Arizona. At the time of the discovery it had been distributed widely in Arizona and New Mexico and limited areas of California and Texas. This seed had been planted in El Paso and Hudspeth counties of Texas. A national survey in 1997 found it present in hard red winter wheat in San Saba County. This year many positive samples were found in San Saba County, due to environmental conditions that favored the fungus. Positive samples were also found in Throckmorton, Young, Archer and Baylor counties.

Two wheat samples were sent to my office recently. They came from loads that were rejected at the elevator because of their offensive "fishy" odor. These samples contained common bunt (stinking bunt), which has a similar "fishy" odor. Distinguishing between the two bunts with a whole grain sample was relatively easy as common bunt typically decays the entire kernel, filling it with black spores. Karnal bunt, also called partial bunt, typically decays only part of the kernel. In addition, common bunt spores are easy to see through with a microscope, but karnal bunt spores are solid black. The bunted grain in both samples filled the whole kernel and they were not black under the microscope. Both were common bunt.

High Plains wheat growers should be concerned about bringing this fungus to their farm. It enters on infested wheat seed, plant parts (hay), livestock, manure and infested soil on equipment. Karnal bunt does not reduce yields as much as other smuts and bunts that are common in Texas. But the concern is not yield reduction. The concern is market reduction. Most wheat producing and buying countries have severe restrictions to prevent movement of karnal bunt into their country. If you bring this fungus into your county, all wheat growers in the county will have great difficulty marketing their grain and will have to deal with a lot of government regulation. This is one disease you do not want!

The immediate concern is disease free planting seed for those who plant in August for grazing. Yes you need to be concerned even if you are not going for grain. If you bring it in, it will spread and be detected very quickly. Do not buy "bin-run" seed even to fill corners or to kill for reduced tillage operations. Buy quality seed of known origin. Avoid any seed grown in the karnal bunt counties mentioned earlier. Every wheat seed that goes in the ground should be treated. Fungicides that control bunts include PCNB and carboxin. Some of the products that include these two fungicides are Terraclor Super X (planter box), Apron-Terraclor Dust (planter box), Vitavax 200, RTU Vitavax-Thiram (planter box), Enhance and Enhance Plus. If you have a lot of seed that you are concerned about, "fishy" smelling or not, I would be glad to take a look at it. Call Harold Kaufman at (806) 746-4053. HK

August 21-22: Sharing the Success, Lubbock Research and Extension Center. Contact Dr. Wenwei Xu at (806) 746-6101.

August 23: 2001 Food-Grade Corn Field Day, Lubbock Research and Extension Center. Dr. Xu is the contact for this one too. Agenda items include a walk-through of the food grade corn plots, corn earworm resistance damage ratings, drought tolerance evaluations and breeding, and many other items. Don't hesitate to call for an agenda. PP