A growing list of pests plague High Plains cotton. As much of the crop reaches cutout, late maturing, irrigated fields will receive the brunt of the remaining pest problems. Beet armyworms continue as chronic infestations across much of the area. High numbers are reported in many fields, especially north of Lubbock. A shortage of certain insecticides has made control more challenging. Bollworm infestations also continue to be reported, mostly of the chronic, sub-threshold kind. High infestation levels are expected to spill out of corn in a week or so. A sprinkling of yellow-striped armyworms, fall armyworms, and loopers have kept it interesting.

The first summer generation of adult boll weevils is producing lots of damage in some fields, especially in Lubbock, Crosby, Floyd, and Hale counties. Record trap catches indicate the explosive potential of this generation. The next generation may overwhelm many of the later maturing fields that have thus far avoided much of the earlier damage. The high trap catches also indicate that there is increased movement between fields. This usually doesn’t start for another couple of weeks. An early maturing crop is partially responsible. GRID maps clearly demonstrate where the worst weevil problems are and the success of the three active eradication zones in keeping weevils in check.

Aphid infestations are finally breaking free from the doldrums of summer and are becoming more of a problem in many fields. Increased insecticide use to address other pests will surely contribute to flare-ups of aphids.

Corn borer egg laying activity is all but over and many larvae are no longer accessible by insecticides. Spider mite infestations are increasing and may need to be factored into any remaining decisions to spray for corn borers.

Many sorghum fields have either greenbugs, yellow sugarcane aphids or corn leaf aphids present. Greenbug numbers are increasing but for the most part have not reached economically damaging levels.

A virtual cornucopia of pestilence

There is some good news but more bad news. The good news is that much of our crop is cutting out and will be beyond the reach of worms and weevils. And there are still some pretty good control options available to producers. Also, the eradication program is working, providing a huge relief to those producers who had enough foresight to vote in an eradication program. The bad news is on several fronts including: beet armyworms continuing to infest area cotton and increasing in severity and scope in some new areas, bollworm infestations continuing with the worst yet to come in corn country, boll weevils exploding in several areas outside of active eradication zones, and damaging aphid infestations popping up in more and more fields.

The Beet Armyworm Problem Continues

Beet armyworm (BAW) infestations have failed to moderate over the past week, continuing the trend since mid June of persistent, chronic infestations at best and acute, heavy infestations at worst. There may be some evidence that BAWs are declining in some areas. This may be in response to the early maturing crop in some cases and the demise of some of our terminally moisture stressed dryland cotton. As was the case in 1980, BAWs are moving with a vengeance into the northern counties where water has been less of a problem and many fields are now providing a succulent salad bar for visiting "beets". The BAW problem may have started in the southwestern counties and persisted there for many weeks, but the worst may be yet to come in the northern and northwestern counties as we move through August.

Short supplies of some of the premier beet armyworm insecticides has caused heart burn for some producers. Intrepid and Denim remain virtually unavailable, and Steward is in very short supply. DuPont is shipping some material in almost every day but supplies have been unable to keep up with demand. From what I understand, there is still plenty of Tracer and Confirm available. I like both of these products and think they perform very well if applied at the right time and with a proper application. First and second instar larvae are the appropriate targets. Not that these materials won’t kill larger worms but it is more difficult to get larger worms to feed in treated areas. For adequate coverage, I believe 5 gallons by air and 10 gallons by ground equipment are the minimum needed.

Where beet armyworms are the only concern and there is some indication that infestation pressure will continue, Confirm fits the bill. Confirm is an insect growth regulator and as such is slow acting. Treated worms stop feeding within 24 hours after ingestion. Most of Confirm’s activity is through ingestion although there is a little contact activity. A Confirm application should not be evaluated for 7-9 days. Otherwise, you will be very disappointed in the apparent results. Just face up to it, Confirm is slow acting. Most folks will not like this. But on the plus side, no material for beet armyworms gives longer control than Confirm---14-21 days on treated foliage versus 5-7 days with other materials. Also, while the label indicates that a rate of 8-16 ounces per acre should be used on larger cotton from mid season on, rates of 4-8 ounces are recommended in our cotton guide and are effective. The 8 ounce rate is what I would use now and has given us 14 day control when applied properly. Add a spreader-sticker to enhance coverage and rainfastness. At these this rate, cost can be about $10.00, a very reasonable price for control.

Tracer fits where bollworms are in the mix. Confirm will not handle the bollworms at these beet armyworm rates. Tracer too is very sensitive to coverage and target size. A word to the wise---don’t cut spray volume. If you cut volume anyway, you must add a surfactant in an attempt to compensate.

Other beet armyworm materials include Lannate, Larvin and Lorsban. Larvin is basically two molecules of Lannate hooked together with a sulfur bond. This increases its residual activity quite a bit but doesn’t necessarily increase efficacy. Lorsban has been effective in some cases and not in others. Why, I don’t know. But if Larvin, Lannate or Lorsban are so good, why have producers, consultants and aerial applicators used the newer, often more expense materials? Some folks are spiking the Lorsban or Lannate with a pyrethroid and singing praises for the concoction. Does this really work? I don’t know, but we at Texas A&M do not have any data at this time that supports this treatment. We do have some earlier data that refutes these claims.

Since last week and my discussion of Capture for beet armyworm control, I have reviewed other pyrethroid labels with the following results. Ammo, Fury, and Capture list "control of BAWs" on their labels, at least for the Texas High Plains. Both Karate Z and Baythroid list "control of 1^st and 2^nd instar BAWs". Leverage, Decis and Asana list "aids in the control of BAWs". The labels for Baythroid, Capture, and Leverage also list "control of aphids" while Karate Z, Decis, Asana and Fury labels also list "aids in suppression of aphids". You figure it out. It’s your field and your problem.

As we move through the month of August, there can be less leaf feeding and more square, bloom and boll feeding. We have already seen this where egg masses are hard to see and hits are virtually invisible. But upon closer inspection, one finds small worms in squares and blooms. Treat these infestations just like bollworms, using a threshold of 10,000 per acre, counting only the smaller worms. Don’t bank on killing any of the larger worms.

How to go about sampling for BAWs? I still think the best method is the whole plant count method. Using beat sheets can easily dislodge many worms in short order but often fails to dislodge the smaller "webbed up" worms and worms with their heads buried in fruit. The beat method tends to underestimate numbers but can provide a quick and dirty snapshot of potential beet armyworm problem fields. The use of hits can be misleading when worms switch from leaf feeding to a diet almost exclusively composed of fruit, leaving very little infestation evidence as you walk down the rows. By checking whole plants, one can get a better estimate of worm numbers, size distribution, percent of plants infested and yes, a count of bollworms too.

How long can this go on? Well in 1980 it went on into mid September. The key is whether your yield is still vulnerable. Any boll that you expect to harvest must have at least 350-450 HUs past white bloom in order to be safe from worm attack.

Bollworm Activity Variable

Bollworm infestation levels are highly variable across the area but are at least continuing to be reinforced through a dribbling in of eggs each day. Sometimes there are enough worms to treat, other times not. And sometimes it is a combination of bollworms and beet armyworms, or boll weevils or aphids that causes us to pull the trigger. It can get very frustrating and expensive in a hurry. I expect the really big bollworm flight to take place over the next 7-10 days, especially in corn country where bollworms have masqueraded as corn earworms for the last two months. While some leakage from corn to cotton has occurred, the bulk of the movement will be later. Pyrethroids will be our mainstay here but aphids and beet armyworms may complicate the situation.

Lots of Other Kinds of Worms in Fields

Fall armyworms, yellow-striped armyworms and loopers have moved in with the bollworms and beet armyworms in some instances. This is the earliest and heaviest yellow-striped armyworm infestation I have ever seen in my 24 years in High Plains cotton. The only ringer in here that could cause trouble is the fall armyworm. It can move in virtually undetected and immediately attack your bolls. I thought this was going to be a problem in 1995 but we dodged the bullet. Hopefully, we will one more time. Loopers are more of a cosmetic and emotional problem. Rarely do they cause sufficient defoliation to affect yield, but boy can they rag up the cotton. Looper eggs are often confused with bollworm eggs and sometimes their larvae are mistaken for beet armyworms. So be careful out there.

Boll Weevils Explode in Some Fields

Boll weevil trap catches have gone up significantly this past week, at least in areas outside active eradication zones (see Table 4 under Eradication Update). Total weevil numbers more than doubled over last week and were at there highest since the week beginning June 19 (Table 1). These F₁ (first summer generation) adult weevils are laying lots of eggs and will seed the next generation of boll weevils, resulting in enough weevils in some cases to overwhelm many cotton fields and producers money pockets. What it comes down to will be whether your field’s harvestable bolls are safe from weevil damage when this next generation emerges. Bolls with 350 HUs or more since white bloom will be safe. Less mature ones will not.

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

*Includes three counties in the Rolling Plains

This level of activity we are observing is two weeks earlier than usual (Table 2). This is because the crop was planted earlier in many areas, squared earlier, got infested earlier and is cutting out earlier. Later maturing fields will be a real challenge as weevils move to concentrate in the lusher fields. Many fields now are reporting punctured square percentages up to the 50% level. This could represent a 4-7 application job to gain the upper hand. But remember that since weevils prefer squares, and many fields have declining square numbers, we are often seeing artificially exaggerated weevil infestation pressure. Once cutout approaches, switch to looking at 100 quarter sized bolls for punctures. A threshold of 15% punctured bolls is the starting point in control decisions. If past peak bloom but before cutout, move the punctured square threshold up to 25-30%.

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

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

Table 3 provides GRID trap data for accumulated trap catch averages since trapping began in April. The trends continue to grow---more weevils this year than last in counties and zones without active eradication programs and dramatic declines in weevil trap catches in active eradication counties or zones.

Keep in mind that none of the standard insecticides used for beet armyworms will control boll weevils. This includes Lannate, Lorsban, Larvin, Denim, Steward, Intrepid, Confirm, and Tracer. Boll weevil materials include methyl parathion, ULV malathion or Fyfanon, Guthion, Vydate, Phaser, Thiodan, Penncap M, Bidrin and even Furadan when used to control aphids. Pyrethroids are also excellent weevil materials but can cause problems by flaring aphids. Both Phaser and Thiodan have extremely short residual and would need to be applied on a 3-4 day schedule rather than the more common 4-5 day schedule of other materials when targeting moderate to heavy boll weevil pressure.

Table 3. Week 31 (week beginning July 31)— Accumulative average number of boll weevils caught per trap in the GRID trapping program starting with week 18.

These 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.

*Includes traps both inside and outside active eradication zones.

Eradication Update

There is no doubt by now that the eradication program is working and working well in spite of the problems inherent in such a large enterprise. The Texas Boll Weevil Eradication Foundation is to be commended for delivering and maintaining this successful program. A quick look at the AgriPartners GRID map for this past week tells the story better than any words that I can write. I did select a few counties either inside or outside of active program areas for a comparison looking at last week’s trap catches (Table 4). The average reduction in trap catches from 1999 to 2000 in these selected counties in active zones between 1999 and 2000 was 78.5% while the average increase in trap catches of selected counties outside of active eradication zones between 1999 and 2000 was 78.6%. This is over a 150% swing! Anyone that says eradication isn’t working has got to be blind.

Table 4. Comparison of last week’s (week beginning July 31) trap catches in selected counties in either active or inactive zones between 1999 and 2000.

Table 5 provides Foundation data on the total accumulative acres sprayed, average number of boll weevils trapped and beet armyworm trap activity. Basically, Foundation traps are also showing significant declines in boll weevil numbers. Their beet armyworm trap catches show a general increase in the Northwest Zone and similar to lower numbers in the two southern zones since the previous reporting period. The Foundation continues to be very cognizant and responsive to the concerns for secondary pest problems. Thus far, the beet armyworm situation has tracked fairly closely to what we observed in 1980. Up to this point, I would be very hard pressed to show any correlation between increased beet armyworm or bollworm problems and eradication activities.

Table 5. High Plains Eradication Program weekly report for week ending July 30.

Aphids Blossom in Many Fields

The time has come for aphids to make their ugly appearance. And they are right on time for this year. Typically, aphid infestations develop over the next 2-3 weeks, peaking some time during that period. This has already begun for some fields. Brant Baugh (Extension IPM Agent for Lubbock County) and I initiated a large aphid control test last Wednesday north of Idalou. We will tell you what works and what doesn’t in our next newsletters. Aphid increases are also being spurred on by the heavy (in some cases) use of insecticides this year. Increasing weevil and bollworm problems over the next few weeks will encourage more pyrethroid use and more subsequent flaring of aphids.

If outside an active eradication zone and you have weevil problems, I would use a straight pyrethroid application followed with a Furadan treatment 5 days later for weevils and aphids. This would fit for situations where aphids are already or are becoming a problem. Remember that you can only make two applications of Furadan this season so save one for later. Other materials can work well, especially Bidrin at the 8 ounce per acre rate. Coverage is critical. The same applies to Lannate. This is a contact only (no systemic action like Bidrin or Furadan) and must contact the aphid or the site the aphid will actually traverse. Often we see excellent control in the top of the plant with Lannate and poor control as we move down the plant. The product kills aphids, the trick is getting it to them. Provado can work too if the cotton isn’t too stressed out by heat or moisture limitations. Otherwise you won’t be happy with what you’ll get from this product. JFL

The not so good news is that spider mites are building, but are still below economic threshold. Banks grass mites are the most common species right now, but twospotted spider mites are present as well.

Mite populations can be flared by some corn borer insecticides, so evaluate fields for mites before choosing a product to control corn borers. Corn borer insecticides commonly used in the area include Asana XL, Capture, Furadan, Pounce, Ambush, and Warrior T. There are a few differences in pesticide selection for mites, and it is essential that you identify which mite species you are trying to control (see insect photos for this section).

First, dimethoate provides Banks grass mite control benefits when added to pyrethroid insecticides. Even when treating smaller Banks grass mite colonies on lower leaves, it is often beneficial to go ahead and add dimethoate to a pyrethroid, even Capture. However, for large colonies at or just below the ear, it is necessary to add dimethoate. Twospotted mites are more difficult to control, and Capture will only provide suppression. A better choice for twospotted mites might be Comite or sulfur.

Mite scouting procedures, thresholds, and a complete list of recommended insecticides are presented in "Managing Insect and Mite Pests of Texas Corn", available on the web at http://entowww.tamu.edu/extension/bulletins/b-1366.html or at your county Extension office.

The economic thresholds for mites are on a sliding scale that takes into account the cost of control and the value of the crop. The economic threshold table is presented below. While this table might look daunting, it is not that bad. An explanation of how to use it follows immediately.

To use this table, first estimate control cost per acre (miticide plus application costs) and the expected value of the crop (yield x price). A two-step mite sampling process is necessary. Sampling should be done at several locations in the field to obtain a representative average.

Step 1: determine the percent of leaves infested per plant. This is accomplished by dividing the number of mite infested green leaves (a leaf is infested if a mite colony of any size is on the leaf) by the total number of green leaves per plant and multiplying this number by 100.

If the percent of infested leaves does not exceed the first (topmost) value in the table, your decision is not to treat. For example, if the control cost is $20 per acre and the crop value is $200 per acre, then control is not justified if less than 59% of the leaves per plant are infested. The topmost of the two numbers tells you whether you need to go to step 2. In the previous example, we did not need to do so. However, if we had 59% or more of the leaves infested with mite colonies, we would need to go on.

Step 2: if the percent of leaves infested exceeds the value in the table, then determine the percent of leaf area damaged by mite feeding. Mite damage is any light colored (chlorotic) area on the leaf that resulted from mite feeding. Dead leaves equal 100% damage for that leaf. If both the percentage of the leaves infested and the percentage of leaf area damaged equal or exceed the values for your crop in the table above, it is time to spray.

If the miticide chosen will not provide maximum control for about one week after application, spray the field immediately. If the miticide to be applied provides rapid control (less than 3 days after application) you can wait up to one week before spraying the corn. That is if your field is just at threshold. Otherwise a delay in control could be costly. RPP

Greenbugs and yellow sugarcane aphids inject a toxin into the leaf. This toxin eventually kills leaf tissue, which shows as dead areas when the leaf is viewed from the top. Greenbug scouting is easy; examine a minimum of 40 randomly selected plants per field each week. Look at the undersides of lower leaves. Greenbugs are seldom evenly distributed within a field, so examine plants from several parts of the field. There is no need to count all the greenbugs, but try to determine whether populations are increasing or decreasing. Thresholds are based on damage, but you should also note the number of parasitized aphids ("mummies") on leaves. These mummies look like bronze colored, swollen aphids, and usually have a hole in the upper part of the abdomen where the parasitoid exited the aphid. The many white, flimsy looking "flakes" in greenbug colonies are not mummies, they are exoskeletons cast off by greenbugs during the molting process. A set of pictures of sorghum aphids, mummies, and cast aphid skins is provided here. When 20% of the greenbugs present are represented by "mummies", 80% of the remaining "healthy" looking aphids are parasitized as well. Don’t treat these fields. RPP

Table 7. Greenbug Treatment Thresholds

Perhaps we can keep the crop moving along with normal to near normal heat unit accumulation and get to the point of safety from many major insect pests. The early set boll load coupled with good growing conditions may be a plus for some growers as we get into late August and early September. RB