Beet armyworms, bollworms and now boll weevils have increased their strangle hold on our vulnerable crop as egg laying activity increased dramatically across much of the area. The juxtaposition of these three pests in the same field will make chemical selection a difficult and costly one. And supplies of Steward and Denim are all but gone from our area. The good news is that we now can use Furadan 4F for aphid control in cotton throughout the High Plains, Panhandle, Northern and Central Rolling Plains areas (Extension Districts 1, 2, and 3). Even though aphid infestations are generally not a concern right now, at least we have one of the best tools available to address any future developing problems.

Southwestern corn borer emergence is well underway with heavy infestations reported in corn in many areas. European corn borer and spider mite numbers are still below levels that cause concern but are increasing. Corn earworm (bollworm) numbers are high in corn with some activity already spilling over into cotton in the northern counties.

Greenbugs have reached economically damaging levels in a few Panhandle sorghum fields. There have been a few reports of yellow sugarcane aphids in seed production fields.

Beet armyworms are becoming a problem in peanuts, dry beans and peas for SpinTor (Spinosad) is already available for the dry beans and peas and a section 18 for Tracer (same active ingredient as SpinTor) has just been granted for use in peanuts.

Beet Armyworm Pressure Increases

Beet armyworm (BAW) infestations over much of the acreage have been at lower levels such as 1,500 to 18,000 per acre when averaged across the field. These numbers can still spell trouble if they persist at these levels for several days and are replaced with similar levels through egg laying recruitment. Recent reports indicate that a big egg lay went down in the cotton north of Lubbock, especially west of Hwy 168. An infestation as high as 219,000 larvae per acre was reported south of Littlefield by Johnna Patterson, IPM Agent in Dimmitt. Now this is an infestation level more reminiscent of 1980, and the first 2000 report of an infestation exceeding 100,000 per acre. This field is also a "no brainer" and needs to be treated promptly. Other fields in the 100,000 to 400,000 are now being reported as well.

Control decisions have been difficult to make in many instances over the last few weeks. Many of our BAW infestations have been in the 4,000 to 20,000 per acre range at any given time and have often persisted at these levels for several weeks. Over time, these chronic sub-threshold numbers can cause significant fruit loss. Like chronic bollworm problems, persistent BAW problems are difficult to address. The most significant complicating factor is whether problems with this pest will continue for much longer and at what levels. If 1980 is any indication, we will be fighting yield-robbing infestations all the way into September. In fact, we treated one infestation near Hale Center on September 12 and made 1 bale of extra cotton per acre over the untreated check. Kind of scary, huh?

I know some producers have treated twice for beet armyworms or at least twice for a combination of BAWs and bollworms. They may be looking at one to two more applications to finish up this year’s crop. Because of this potential to spend a lot of money for worm control this year, I have been very cautious in spraying too aggressively at first. Many of the BAW infestations I have observed have had a tremendous amount of leaf feeding and very little fruit damage. This is where a prudent approach is advisable. A threshold in excess of 20,000 per acre is advised. If, on the other hand, BAWs are forgoing much leaf feeding and vigorously attacking squares, blooms and small bolls, then a threshold more attuned to bollworms will be the correct approach. This appears to be the case in the southern counties this year, where Gaines, Yoakum and Terry county beets are grazing on a lot of fruit. Only you can assess the level of fruit feeding. Don’t make your decisions based only on visible leaf feeding damage or the presence of "lots of worms in spots".

Beet Armyworm Insecticides

Much of the beet armyworm activity had been concentrated in the more stressed fields, and fields with skiprow planting patterns. I would also expect that surveys would show more activity in dryland, lower yielding fields since these are the fields that can ill afford much money spent on insect control. This is also true of late planted fields where BAWs have also taken up residence. Most irrigated fields have been treated or were planted to Bollgard varieties that have done an excellent job of suppressing damage. The more recent BAW egg lays are now spreading into our lush, irrigated fields.

Supply is getting short for some of the newer BAW materials. Intrepid is basically unavailable. Denim supplies are running out and probably will be unavailable once you read this. Steward so far has kept up with demand but supplies are running short. With the absence of Denim and the increased BAW activity reported, Steward should be gone by this weekend. So far there seems to still be a good supply of Tracer. Why Tracer hasn’t been used much is anyone’s guess. But I suppose that some early inconsistent results (1997 and 1998 tests where coverage may have been suspect) and its full label status versus the section 18 status of Denim and Steward, may have been some influence on use. Many folks still think that section 18 materials have to be better than registered materials. Confirm, Larvin, Curacron, Lannate and Lorsban are all still available.

FMC has been pushing Capture for situations where bollworms, "beets" and the threat of aphids is present. This is their most expensive pyrethroid, compared to Fury and Ammo. A price reduction this year has made it more affordable but it is still an expensive pyrethroid. So what about FMC’s claims? Capture used to control aphids as well as anything did several years ago in my tests but infestations came back quicker than those controlled by organophosphates. But Capture became more like other pyrethroids in very short order, failing to control and even flaring aphids. What FMC is banking on this year is that aphids will be susceptible on the first application and stay suppressed following the application.

As far as FMC claims for beet armyworm control---all pyrethroids provide some measure of suppression when timed to target small larvae. But this is more suppression than control. Capture may be able to claim higher levels of suppression of BAWs than some of the other pyrethroids, but certainly would not provide control at levels observed with Tracer, Denim or Steward. Capture is a very good bollworm material, but so are most of the other pyrethroids as well. Bottom line? I wouldn’t bank on it to control a serious beet armyworm infestation, nor would I use it to control aphids. I have not seen it compared to Leverage as far as aphid control. As you know, Bayer’s Leverage is a formulation of Baythroid and Provado (which is in our guide for aphid control). I would expect Leverage to do as well or better than Capture. But I don’t know.

One interesting note. Several folks have noticed pale colored (yellowish) BAW larvae on Bollgard cotton. Often times, these larvae are webbed up. I think this may be symptomatic of the Bt effect on these caterpillars which have stopped feeding and are slowly dying. We have been encouraged by the level of control that Bollgard cotton has provided for beet armyworms. We were expecting about 25% control but have observed 30-40% control in many instances.

Heavy Bollworm Egg Lay In Progress

Bollworm egg laying activity had generally subsided across much of the area but has now picked up dramatically, first in the northeastern High Plains, around Quitaque, Turkey, Clarendon, Memphis, and Wellington areas; and now in the High Plains area as well. Egg numbers as high as 150,000 per acre have been reported. Now this is a serious egg number! With "beets" in the mix and concern for flaring aphids, insecticide selection could be quite challenging. Unless the BAW numbers are high enough, I might not factor them in so much into the control decision. The main concern is for good bollworm control with maximum residual control.

Any of the pyrethroids could deliver excellent control but could also flare aphids and would not control beet armyworms. Leverage might be the ticket where aphids are a concern since the recommended rate range for bollworms would include 3.0 to 3.75 ounces of Provado (based on the Leverage label and using comparison units for the Provado label). Our recommendation in the guide for aphid control is the high end of this Provado use range. Provado sometimes is erratic in control delivery, especially when cotton is stressed. Also in the hunt would be a mixture of a pyrethroid with Lannate. The addition of Lannate would push the aphid numbers down and provide some bollworm and beet control. A mix of Lannate and one of the beet armyworm materials may also be a possibility as long as the bollworm numbers were not too high. Also consider Lorsban. This product can provide good control of BAW infestations that are not too far above threshold, 65% suppression of aphids and some bollworm control.

Boll Weevil Activity Erupts Across Area

Boll weevil activity in fields is on the increase as more summer weevils emerge from squares. Emergence of overwintered boll weevils has again decreased significantly last week (Table 1), further reinforcing my contention that we are past this generation and should focus our attention on this first summer generation. But trap catches in the Southern High Plains/Caprock Zone went up this past week (Table 2). Compared to this same week in 1999, we caught over double the number of weevils in the GRID last week. This trend is continuing into this week (week 30) too. Of the five eradication zones (3 active and 2 inactive), for week 30, the Northwestern Zone showed a decrease in trap catches (84%) compared to 1999 levels. The Western Zone and the Permian Basin Zone had smaller decreases, 39% and 34% respectively. The 2 inactive zones had the following increases: Northern, 79%; Southern High Plains/Caprock, 76%. This last zone figure is down from 338% increase calculated from last week’s trap catches.

Table 1. Total boll weevils caught per week and percent of traps catching boll weevils since April 24, 2000 in the GRID trapping program.*

Week beginning	Total weevils caught	% of traps catching weevils
April 24	948	30
May 1	887	34
May 8	5243	67
May 15	1112	34
May 22	2106	45
May 29	1651	46
June 5	4163	56
June 12	3391	47
June 19	5684	49
June 26	3346	53
July 3	3318	48
July 10	2057	32
July 17	1522	42
July 24	1772	41

*Includes three counties in the Rolling Plains

Table 2. Comparison of average weekly boll weevil trap catch in the Southern High Plains/Caprock Zone between 1999 and 2000.*

Week beginning	1999	2000
June 5	12.2	6.8
June 12	7.8	6.1
June 19	9.9	4.1
June 26	9.5	6.0
July 3	3.3	4.6
July 10	2.0	1.8
July 17	2.1	5.1
July 24	2.0	6.0
July 31	5.8
August 7	5.5
August 14	13.7

*This data represents the average number of weevils caught per trap catching weevils. Zeros are not counted.

The level of decreases in the two active southern eradication zones is less than I would have liked to see but considering the numbers we are observing in inactive eradication zones compared to last year, these are huge reductions!! Why are we seeing weevils in eradication fields this early? Because of the late freeze last year, the mild winter, the extended emergence this year, the early crop, and early season conditions favoring high weevil survival; first summer generation boll weevil numbers are much higher than we have ever seen before. And much earlier too. Even though accumulative trap catches in most counties are falling below those observed in 1999 (Table 3), this is mostly a reflection of the emerging winter population and does not yet reflect the full impact of the summer generations. This too will change.

What is most disturbing are the high trap catches of first summer generation boll weevils in fields that are well into blooming and have yet to cut out. As many as 10 per trap per day have been caught on the Experiment Station. Normally, we would expect boll weevils to pass by the traps, feed on the squares and bolls in the fields soon after emergence from infested squares. They would then produce pheromone, making the field even more attractive than the trap to further weevil captures. What this tells me is two things: 1) There are a lot of adult weevils flying around out there. 2) There are many fields in the general area that are cutting out early, encouraging weevils to seek food elsewhere. Remember that once boll weevils colonize a field they rarely leave in any numbers until the food supply becomes limiting or later in the year (mid August) when inter-field movement usually occurs.

The big question that is or will be on everyone’s mind is why are we seeing economically damaging boll weevil infestations in fields in July when we put on one or more overwintered boll weevil applications earlier? Doesn’t the data indicate that properly timed overwintered boll weevil applications delay the appearance of damaging infestations until later in August? Yes, but---with an extended emergence, an early squaring crop and a very high survival rate of weevil grubs in squares; all bets are off.

Punctured square counts have blossomed from below 5% last week to over 30% in several instances this week. This is serious stuff! Our threshold is 20% punctured squares. This higher level of activity will take at least 2 applications to bring back control. After peak bloom, the threshold should be elevated at least to 25% punctured squares. Once cutout approaches (5 Nodes Above White Flower) then small bolls will need to be sampled. Decisions based on punctured squares will be overly inflated since declining square numbers will put weevils in competition for a limited supply of their preferred fruit. Once cutout is reached (NAWF=4) bolls will be generally safe from weevil damage when 350 heat units or more are accumulated. At the present HU accumulation rate, that would take about 2 - 2 1/2 weeks.

Table 3. Week 29 (week beginning July 17)— Accumulative average number of boll weevils caught per trap in the GRID trapping program starting with week 18.

Location	1999	2000
Northwest High Plains	39.3	18.7
Northern High Plains	67.9	58.9
Southern High Plains	95.3	63.9
Western High Plains	194.6	28.0
Permian Basin	99.6	32.2
Andrews	173.9	28.1
Bailey	42.7	18.3
Borden	71.4	45.3
Briscoe	80.3	64.5
Castro	12.9	7.7
Cochran	72.8	61.2
Crosby	123.4	108.1
Dawson	134.9	45.9
Deaf Smith	9.0	2.0
Floyd	52.3	88.8
Gaines	246.1	23.2
Garza	178.2	128.3
Hale	58.3	55.9
Hockley	56.5	32.9
Howard	101.3	22.0
Lamb	44.4	17.2
Lubbock	70.6	57.0
Lynn	77.7	32.8
Martin	48.0	14.2
Midland	38.5	16.2
Parmer	8.9	5.0
Swisher	59.9	42.0
Terry	129.0	23.3
Yoakum	163.5	23.5

This data represents the average number of weevils caught per trap catching weevils. Zeros are not counted. Refer to the Plains Cotton Growers, Inc. web page for actual total numbers caught and percent of traps catching weevils each week.

Eradication Update

The Texas Boll Weevil Eradication Foundation continues to apply insecticidal pressure to the first summer generation of boll weevils. They have had to play Russian Roulette with beet armyworms and in some cases bollworms, in an effort to avoid worsening the worm situation with their ULV malathion sprays. So far their strategy appears to have worked out. But with the increase in both bollworm and beet armyworm pressure this week, the Foundation will have to back off from their more aggressive trap triggers in more work units, especially as weevil pressure increases. This will unfortunately reduce the pressure on boll weevil populations. While this scenario may bother producers in active zones, the alternative of "blow away" bollworm and beet armyworm infestations with a shortage of insecticidal tools for control should frighten growers even more. Especially when looking at application costs of $20-$30 a pop.

A new concern of mine is the early cutout of much of our crop. This will put a lot of pressure on boll weevils trying to fatten up before departing fields for overwintering sites this fall. If pushed into these sites too early, these weevils will not survive to see squaring cotton next year regardless of how fat and healthy they are. But just as important is whether the Foundation will be inclined to begin diapause treatments on the earlier fields that will have open bolls by the second week of August. Weevils from these early maturing fields will be relatively unimportant as far as eradication is concerned. We would be better served if the Foundation delays most treatments until after September 1st, after which the really important overwintering weevils begin to depart fields. An earlier start this year could result in serious budget overruns as well. I have every confidence that the Foundation will make the right call on this.

Furadan 4F Released for Aphid Control

Cotton aphid numbers remain highly variable across the area although there is increasing evidence that more reproduction is taking place(cotton aphid and damage pictures). I think the recent high temperatures have taken their toll. A predicted cooling down period this weekend might provide the trigger for aphid infestations to begin to take off. There are some fields out there that are experiencing significant increases in aphid numbers, especially as one moves toward the Caprock and off into the Rolling Plains. On July 27th, I received reports on 4 fields from Briscoe County where control was less than adequate. This was sufficient information for me to request that Furadan 4F be released for Extension Districts 1, 2, and 3. The Texas Department of Agriculture approved this request and producers can now use this material for aphid control. Please pay attention to the label and the section 18 information. Be sure to post fields that are treated and observe the worker re-entry intervals.

Don’t forget that there are other aphid control materials at your disposal including Bidrin, Lannate and Provado. Lorsban and Curacron are also listed in our guides but usually provide less control than the previously mentioned three. Furadan is often chosen because of its lower price and more consistent high level of control.

Keep an Eye Out for Plant Bugs

Fleahoppers (FH) and western tarnished plant bugs (WTPB) continue to pose problems for late planted fields (FH and WTPB) and fields near favorable alternate hosts (WTPB). Once fields are blooming and if earlier fruit retention has been good, then the threshold for WTPB needs to be increased from one to two WTPB per 3 row feet (based on drop cloth sampling). The ULV Malathion used by the Foundation has had some impact on decreasing FH numbers and to a limited degree, WTPB numbers too. JFL

Spider mite numbers are building slowly. Whether problems develop will depend a lot on the weather in the next 4 weeks. Next week's edition of FOCUS will discuss spider mites in depth. RPP

Succulent and dry beans and peas are also at significant risk from BAW. The toolbox for control of BAW on these crops has been improved in the past few months with the addition of SpinTor 2SC (same active ingredient as Tracer). However, because this is a recent approval, the SpinTor labels for beans and peas did not make it into many of the year 2000 pesticide references. The supplemental labels are available on the web at http://www.dowagro.com/coastal/home.asp.

Sorghum entering bloom should be monitored for midge on a daily basis, and it is time to start monitoring greenbugs. Carl Patrick (Extension Entomologist, Amarillo) reports that a few fields have reached the greenbug economic threshold to our north. An insecticide application to control greenbugs is justified on sorghum in the boot to heading stage with the death of one functional leaf on 20 percent of the plants. Yellow sugarcane aphids have been reported on seed production sorghum in the Hereford area. These aphids inject a toxin into the leaf, and by the time leaf yellowing damage shows up, significant loss has occurred.

Fall armyworm continues to impact several sorghum fields, and can also damage grass pasture and alfalfa. RPP

What does early cutout in irrigated cotton mean? It means this crop got off to an awesome start with a very heavy fruit load due to our June rains and high retention rates. The damaging infestations of fleahoppers and plant bugs that plagued last year’s crop did not materialize this year. The June rains may have also leached nitrogen out of the root zone in some instances and created excessive leaf area. All these possible factors put the plant on an early cutout course, especially once water demands could not be met.

This earlier maturing crop isn’t necessarily all bad. Sure, it could limit yields by denying producers the opportunity to capture late season HUs for a later boll crop. But it will be positive in that it will limit late season insect damage and control costs. JFL

Crop water demand is now at or near peak levels, with high PET demand (see below) and crop stages near their maximum consumptive use stages. Many of our crops are at critical water use stages, in which yield is especially affected by drought stress; hence soil moisture monitoring is very important right now. Shallow soils and sandy soils with low water holding capacity need to be monitored especially close, as drought stress can occur quickly in these soils. The following guidelines compiled from a variety of sources may be helpful in irrigation management decisions. Soon we will be addressing irrigation termination in this FOCUS segment.

Corn: Corn is more sensitive to water stress than most other field crops. Although corn roots may reach a depth of 5-6 feet in a deep soil, it extracts most of its water from the top 2-3 feet (40% from the top 1/4 of the profile; 30% from the next 1/4 of the profile). Generally speaking, the effective root zone is limited to 3-4 feet until late in the season. The most critical period of water management in corn centers around pollination. The highest seasonal water use occurs from about 2 weeks before to 2 weeks after silking. Water stress during silking will result in the greatest yield reduction. Water requirement remains high during the early stages of grain development, often described as the "blister kernel" and "milk" stages.

Reference: Benham, Brian. 1998. Irrigating Corn. NebGuide G98-1367. University of Nebraska Cooperative Extension Service. http://www.ianr.unl.edu/pubs/fieldcrops/g1354.htm

Cotton: Cotton is more drought tolerant (and salt tolerant) than most other agronomic crops. According to Charles Stichler, Extension Agronomist at Uvalde, water supply during early squaring has a greater impact on yield than at any other time. This is the time during which the number of seed per boll is determined. Early water stress encourages earliness; it leads to reduced plant size, early bloom and early cutout. Stichler recommends that early season water stress be avoided for short-season cotton. Early irrigation termination, however, helps to promote good defoliation and reduce re-growth. Like most other crops, cotton will extract most of its water from the upper 2-3 feet of the soil profile.

Grain sorghum: A relatively drought-tolerant crop, grain sorghum develops an extensive root system, which can extend to 6 feet in a deep, friable soil. About 75% of water uptake will be from the top half of the root zone (about 3 feet); under water stress conditions, it can effectively utilize water from deep in the root zone. Because of its drought tolerance and good yield response to limited irrigation, sorghum is often a good choice for irrigators with low-capacity wells. Sorghum is more salt tolerant than corn.

Reference: Grain Sorghum Production Handbook. Kansas State University Agricultural Experiment Station and Cooperative Extension Service.http://www.oznet.ksu.edu/library/crpsl2/c687.pdf

Peanuts: Water use by peanuts is low early in the season, but water consumption during the reproductive period is high, declining as the pods begin to mature. During the bloom period, water stress can delay formation of flowers. Under extreme drought conditions, flowering can be completely inhibited. After bloom, peg penetration into the soil requires adequate moisture. Water use by peanuts generally peaks in early to mid August; most of this water is extracted from the top 2-3 feet of the root zone. After pods are set, irrigation can be reduced, but moisture should be maintained to allow peanuts to mature.

Reference: Texas Peanut Production Guide. 1998. B-1514 Texas Agricultural Extension Service. http://agpublications.tamu.edu/pubs/esoil/b1514.pdf

Soybean: The most important time for soybean plants to have adequate available water is during pod development (R3-R4) and seed fill (R5-R6). If the soil is at field capacity moisture content at planting, irrigation may be delayed until full flower stage (according to the University of Nebraska guidelines). In sandy soils and in water limited areas, irrigation may be needed earlier, especially during flowering. If water is applied during flowering, it is necessary to follow up with adequate irrigation during seed fill, to avoid development of small seeds and reduced yield. Soybean roots can reach depths of 5 to 6 feet, but most of the water extraction occurs in the top 2-3 feet of soil. Soybeans yield better in soils with good internal and surface drainage. According to North Plains PET Network data (Dimmitt station), estimated potential water use last week for soybean ranged from 0.2 inches per day (V2 stage) to 0.37 inches per day (R4 stage).

Reference: Benham, B.L., J.P. Schneekloth, R.W. Elmore, D.E. Eisenhauer, and J.E. Specht. 1998. Irrigating Soybean. NebGuide G98-1367. University of Nebraska Cooperative Extension Service. http://www.ianr.unl.edu/pubs/fieldcrops/g1367.htm

Potential Evapotranspiration (PET) Estimates

Estimated maximum crop water demands, based upon PET weather station data, are summarized in Table 4. (Electrical problems have resulted in unreliable data at the USDA-ARS weather station in Gaines County, hence the Seminole station data have been omitted from this summary. We hope to have this station’s data corrected soon.)

Table 4. Data from the South Plains PET Network, July 20 – July 26, 2000:

[a] Potential Evapotranspiration, often referred to as "PET", is an estimate of crop water demand based upon weather data. Actual water use by a crop, referred to as "crop ET", will vary with soil and crop conditions, and often will be less than the crop’s PET.

PET varies with growth stage (planting date and accumulation of heat units) and crop. You are encouraged to customize your crop water use estimate by multiplying the reference PET value by the appropriate crop coefficient. Crop coefficients for additional crops and growth stages are available from the Texas PET Website at the following:

High Plains Corn - http://texaset.tamu.edu/include/crop/corn.html

High Plains Cotton - http://texaset.tamu.edu/include/crop/cotton.html

High Plains Sorghum - http://texaset.tamu.edu/include/crop/sorghum.html

Other Crops - http://texaset.tamu.edu/include/crop/cropcoe.html

Turf — http://texaset.tamu.edu/turf.asp

PET data and weather data for Halfway, Lamesa, Lubbock, Seminole, and Ropesville are available at: [http://achilleus.tamu.edu/data/data.html].

The Northern High Plains PET Network provides detailed PET estimates by crop and by planting date for Bushland, Dalhart, Dimmitt, Earth, Etter, Farwell, Morse, Perryton, Wellington, and White Deer. Current data are available at http://amarillo2.tamu.edu/nppet/station.htm. DP

Focus on Entomology is published by the Texas Agricultural Extension Service Route 3, Box 213AA Lubbock, TX 79403 For more information call or e-mail: 806-746-6101 or m-coffman@tamu.edu Editor: James F. Leser Web Site Layout: R. Pat Porter Production: Michelle Coffman Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socio-economic level, race, color, sex, religion, handicap or national origin. The information given herein is for educational purposes only. References to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.