Fields lost to hail and replanted back to cotton may miss overwintering boll weevil emergence but could suffer later in the season when weevil numbers are at their highest. Boll weevil numbers remain relatively lower than last year but fields near towns and prime overwintering sites will generally see enough pressure to warrant one or more insecticide applications during the early squaring period. The eradication program is gearing up as more fields begin to square. Not much acreage has been treated so far. Thrips remain a problem for some fields but variation in infestation levels and crop condition between fields still requires scouting for management decisions. Many earlier planted fields are squaring, which means producers and consultants must be on the lookout for fleahoppers and plant bugs. Early square loss to these pests means big headaches later in the season. Remember last year? Our first bollworm egg lay is underway. Hopefully their numbers will remain low and high temperatures will provide a lot of heat mortality. Beet armyworms and another yet to be identified caterpillar are causing some concern in the southern areas near the New Mexico border. Grasshoppers pose a threat but as yet have not developed into the problem reported east of our area.

Corn continues to grow under relatively pest free conditions with the help of weather that has been unfavorable for mite infestation development. A southwestern corn borer moth flight is currently underway but field infestations remain light. Ovipositing corn earworm moths are concentrating in corn and staying out of nearby cotton.

Peanuts have light caterpillar activity and some non-yield threatening thrips damage. Southern Blight has been found but has yet to infect vegetative growth of peanuts.

Corn earworms are reported in ears of early planted sweet corn while spider mite infestations have been found on lower leaves of tomato plants in the Lubbock area. Potato psyllids are being found in low numbers in untreated fields and potato early blight is a developing problem for many Springlake potato fields.

Ugly Cotton Could Mean Thrips

Thrips continue to be a pest of concern this week although many early planted fields have reached a point where thrips no longer pose a threat. Once cotton reaches the 5th or 6th true leaf stage, thrips control rarely pays unless the plant had received earlier severe damage (either from thrips or weather). Open, sunny weather will also decrease the need for thrips control as thrips tend to spread out on the plant rather than concentrating their feeding in the terminal area where damage is most pronounced.

The recent rains will also have reduced thrips numbers in many instances but thrips numbers can rebound in a short time. These same rains will most certainly have washed some of the soil-applied insecticide out of the plant’s root zone, effectively reducing residual activity. If your field received more than one or two inches, don’t expect much insecticide activity to remain, especially in the sandier soils. If additional treatment is needed, banding insecticides on is still the best way to go if your goal is to keep costs under control. A ten inch band on 40" row spacing cuts insecticide costs by 3/4ths.

Got Weevils?

GRID trap catches went up last week, sending an alarm out to producers that they need to be watching their situation very closely as their cotton begins to square (Table 1). Except for the high numbers caught the week of

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

May 8, the general trend is for increasing emergence. Suicidal emergence may not be very high this year. Still there are many areas in which trap catches remain very low. That is why we trap individual fields and do not rely on trapping information of others (such as the GRID) to make management decisions. The trend remains the same as last week where average accumulative weevil trap catches are at or below 1999 levels (Table 2). The "A" list of 10 counties catching the most weevils includes: Borden, Briscoe, Cochran, Crosby, Floyd, Garza, Hale, Hockley, Lubbock and Swisher. Notice that all of these are outside active eradication zones. Also, six of these counties have trap catches approximately the same or higher than last year. See also the actual county-by-county trap catch records and distribution maps based on the GRID trapping program.

Table 2. Week 23 — Accumulative average number of boll weevils caught per trap in the GRID trapping program starting with week 18.

Location	1999	2000
Northwest High Plains	15.8	10.4
Northern High Plains	42.4	36.4
Southern High Plains	60.7	36.1
Western High Plains	132.3	13.6
Permian Basin	65.6	11.7
Andrews	132.5	13.2
Bailey	13.6	10.5
Borden	33.5	29.0
Briscoe	45.9	33.9
Castro	5.5	4.0
Cochran	43.8	40.6
Crosby	89.8	54.9
Dawson	73.2	15.0
Deaf Smith	4.0	0.0
Floyd	28.5	29.2
Gaines	175.2	11.0
Garza	112.4	51.7
Hale	37.6	36.4
Hockley	29.3	21.9
Howard	72.4	10.2
Lamb	18.9	10.5
Lubbock	44.0	37.4
Lynn	43.7	16.9
Martin	30.2	8.0
Midland	23.8	7.6
Parmer	5.7	3.0
Swisher	34.6	23.7
Terry	88.4	13.3
Yoakum	99.2	13.8

These data represent 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.

Many fields have entered the vulnerability stage for boll weevil damage and most importantly, their egg laying activities. In most instances, the goal of overwintered boll weevil control is to delay the development of economically damaging infestations, hopefully until late August or even later. Under the worst case scenario, when weevil numbers in traps run in the double digits, early weevil control may even be necessary to prevent loss of all early squares and even plant terminals. For the most part, when trap catches average two or more weevils per trap the week pinhead-size squares appear, control is warranted. This is especially true in irrigated fields were survival and reproductive success is highest. The trap index used for dryland fields may be a little more conservative, perhaps as high as four per trap. These fields will have a lot of heat mortality to grubs in fallen squares. If weather conditions the week of decision making suppress trap catches (high winds, cool temperatures and rainfall events), then look at the previous week’s numbers.

If you are running your own traps for overwintered boll weevil control decisions, make sure you change out the pheromone patch at least every two weeks. When temperatures approach 100° and constant high winds are a problem, pheromone release could be accelerated, necessitating a more frequent change in pheromone patches. If you don’t do this, your trap catches will go up and down weekly, and not reflect the true picture of weevil numbers.

If trap numbers average 4 or more per trap week, especially on irrigated fields, you can bet you will need a follow-up application in 4-5 days. Trap catches of 10 or more per trap week could mean a three application program for overwintered boll weevil control. Don’t mess around with this program. Too few applications, a missed application or too wide an interval will spell trouble, expensive trouble later on. Early applications can be banded on at a considerable savings over the later broadcast applications. I would use something like Vydate to help preserve beneficial arthropods but still get good control of boll weevils. If you are looking at the possibility of multiple applications based on early trap catches, I would consider using methyl parathion, ULV malathion, or Guthion. These materials will often cost less but will be more detrimental to the "good guys". But multiple applications of Vydate on a 4-5 day schedule will also "slam" your "beneficials".

I would not rely on scouting to determine if a field needs to be treated for overwintered boll weevils. Adults are very hard to find. As squares increase in size, you will observe that damaged squares often flare open prior to being shed. Usually there is some bright yellow pollen associated with this damaged square. Don’t confuse this with a bollworm damaged square, which can also have flared bracts. Usually there will be grains of frass (insect excrement) associated with this damage. This frass will be more brown or straw colored rather than yellow. View photgraphs of boll weevil and bollworm damaged squares. As weevils establish in a field, and adults for the first summer generation appear, you should find "red" adult weevils (picture). These are the newly emerged weevils that will eventually take on the more classic gray color.

Activities of the Texas Boll Weevil Eradication Foundation have picked up over the last several days. Acreage meeting the criteria for overwintered boll weevil applications (based on a trap index and crop stage), has ballooned as weevil movement out of overwintering sites has escalated and fields have entered the squaring stage. Growers that would rather treat their own fields at their expense often substitute Vydate for the ULV malathion application in an effort to preserve beneficial insects and minimize the risk from secondary pests. Another scenario has developed for a few fields down south where bollworm numbers are sufficient to necessitate control. When a field must be treated for both weevils and bollworms, pyrethroids are usually the best bet. But because pyrethroids were not on the approved list of insecticides (not in the Texas A&M cotton insect guide), the Foundation could not sanction the treatment. That has all changed. Synthetic pyrethroids are now in the west Texas cotton insect guide for both in-season and overwintered boll weevil control and can now be used as an option for weevil control when Foundation traps indicate a field needs treatment. The second mandatory application should be with a lower cost material such as methyl parathion or Guthion.

Foundation traps are about as common as West Texas hail stones. These traps are on square wooden poles (picture of trap) and need to be placed around the entire perimeter of the cotton field to be most effective. Please help the eradication program by providing access to all sides of your fields. Sometimes a circle is planted in more than one crop. When this happens, traps will often be placed around the outside perimeter, even the corn or sorghum. This could look like the Foundation is trapping a crop other than cotton but in truth they are trying to get as close to that side of the cotton as possible. There are other traps in the area run by consultants, producers, Texas Tech University and in the GRID trapping program of the Texas Agricultural Extension Service and Plains Cotton Growers, Inc. Most of these will be on a heavy gauge wire pole and marked as to ownership.

Square Thieves On The Move

No news is often good news. I had heard very little about fleahopper and plant bug activity over the last several days. Needless to say I am holding my breath after last year when fleahoppers and plant bugs were serious problems for many of our cotton fields. Not only do these pests rob us of valuable yield, but they also eliminate crop earliness and increase the probability of more problems with later season pests.

With many fields entering the squaring stage, it is important that producers and consultants monitor plants for square retention. Our current threshold is 25-30 fleahoppers per 100 terminals combined with less than 90% square set the first week of squaring. After two weeks, square retention should be around 85% and 75% once blooms begin to appear. While environmental conditions can cause loss of small squares, insect counts can verify whether fleahoppers or plant bugs are the culprits. Cotton fleahoppers are tiny pests, about 1/8 inch long as winged adults (picture). Nymphs, recently emerged from eggs inserted in plant tissue are much smaller and cannot fly. Nymphs avoid detection by running down the plant stem while adults take flight as you approach the plant. Plant bugs, most commonly the western tarnished plant bug, also have wings as adults but are wingless as nymphs (pictures of adult and nymph). Their adult size is one-quarter of an inch long. Both fleahopper and plant bug nymphs are pale green in color.

Fleahoppers and plant bugs have piercing, sucking mouth parts which remove fluids from squares resulting in blasted squares and eventually scars where squares have been shed a few days after they were damaged (pictures of damage). Squares vulnerable to fleahopper attack are no larger than pinhead in size. Plant bugs can attack and damage all sizes of squares, blooms and small bolls. They are a pest that can be with us for much of the season.

Both fleahoppers and plant bugs migrate into cotton as it begins to square. They have many alternate hosts. Fleahoppers are commonly found on silverleaf nightshade (whiteweed) and lanceleaf sage (mint weed). Plant bug alternate hosts can include these weeds but also alfalfa, potato, clovers, vetches, mustard, dock and many others. If you are spraying herbicides for any weed hosts in your cotton fields, you should consider adding an insecticide. After all, where do you think the fleahoppers and plant bugs go after you kill the plants they are on?

For now, we will be using a drop cloth to sample for plant bugs (see page 7 of cotton insect guide for instructions on making and using this sampling device PDF file). During the first week of squaring the threshold is one lygus bug (adult or nymph) per 3 feet of row combined with less than 90% square retention. For the second and third weeks prior to bloom, the bug number remains the same but square retention can drop to 85% and 75%, respectively. Since adults of both species (but especially lygus bugs) can freely move into and out of a field, scouts may find damage but no responsible bugs. Then nymphs can magically appear a few days later. Frequent field inspection is the only way around this problem.

Early Caterpillars Bring Concern

Several caterpillar species have been reported in area fields, especially south of Lubbock. The High Plains is currently under its first wave of bollworm activity as evidenced by increased trap catches. Eggs are being found in southern fields but most northern egg laying activity will be concentrated on corn, not cotton. While most of you can identify a bollworm larva, don’t confuse it with another caterpillar, which usually makes its appearance early in the season. The cotton square borer is a butterfly with a larva that can be bright green and slug-like in appearance (pictures of adult and larva). The larva infests many legumes as well. Square damage appears as a very clean hole, like that produced by a drill, as opposed to that of a bollworm, which is more ragged and "dirty".

Beet armyworm infestations continue to be bothersome in some instances with infestations of early instar larvae as high as 60,000 per acre reported near the New Mexico state line. Most of the time these early infestations collapse in pre-blooming cotton and under a high temperature environment. If they don’t, an insecticide application would be warranted. Lorsban has often worked well, especially in smaller cotton and early in the season. Other materials to consider are Confirm, Intrepid, Tracer, and Denim. Go for good coverage and smaller worms.

Clyde Crumley, IPM Agent in Seminole, has reported a very small caterpillar that we have yet to identify. Initial damage was to young leaves, yet to unfurl. But Clyde has now found what appears to be square feeding by this pest. Up to 16,000 larvae per acre have been found. Identification is difficult for such small larvae but we are trying. It doesn’t look like a bollworm or armyworm to me. Maybe more like a garden webworm (careless weed worm). We will keep you posted.

Watch Out For Grasshoppers

Grasshoppers pose a serious threat to crops in some area of the Rolling Plains and Central Texas. While there have been reports of grasshopper infestations in some of our pastures, their numbers have not approached the 25-40 nymphs per square yard reported to the east of us. The most common species has been the differential grasshopper which can move into the edge of a cotton field and "mow it down" (picture of differential grasshopper and damage). Again, I’ll keep you posted. JFL

How Much Does A Non-Bt Refuge Cost?

Bt corn can be planted on up to 50% of corn acres on a farm this year according to new EPA regulations for this part of Texas. As anyone who has used Bt corn knows, it is superb for control of SWCB and European corn borer (ECB) (but does not control rootworms, aphids, spider mites, grasshoppers, and many other pests). Most of the country has a 20% non-Bt refuge mandated by EPA, but because Bt cotton can be used in our area, EPA set a higher refuge for corn as part of a resistance management plan for the CEW (also known as the cotton bollworm). This makes sense from a resistance management standpoint; CEW is subjected to two generations of selection on Bt corn, and then one or two more on Bt cotton. The idea is to lower the exposure to Bt in corn before moths move to cotton.

The relatively large refuge in Texas corn is scientifically justified, and will help preserve our ability to control CEW with both Bt corn and Bt cotton. However, many growers wonder how much money they will lose if they have to plant a 50% non-Bt refuge instead of being able to plant all their acres to Bt corn. The answer is "not much" according to a new study done by Kansas State University, even in areas with significant SWCB populations. Using standing yield and total yield (where lodged corn was picked up and harvested with standing corn) data from Bt and non-Bt corn that was either sprayed with Capture ($21.20 per acre cost) or left unsprayed, Kansas entomologists and economists were able to estimate the economic costs of a 40% non-Bt refuge.

Table 3. Comparison of returns to different corn production systems in two Kansas locations.

Production System	Total Returns ($)	Increase in returns ($) [b]	% Increase [b]	% Decrease [c]
Comparison Based on Standing Yields
100 acres of unsprayed non-Bt corn	33,312	--	--	--
100 acres of sprayed non-Bt corn	38,224	4,912	14.75	--
40 acres of sprayed non-Bt corn plus 60 acres of unsprayed Bt corn	40,667	7,355	22.08	3.85
100 acres of unsprayed Bt corn	42,296	8,984	26.97	--
100 acres of sprayed Bt corn	42,264	8,952	26.87	--
Comparison Based on Total Yield
100 acres of unsprayed non-Bt corn	40,850	--	--	--
100 acres of sprayed non-Bt corn	41,725	736	1.88	--
40 acres of sprayed non-Bt corn plus 60 acres of unsprayed Bt corn	43,540	2,502	6.38	2.75
100 acres of unsprayed Bt corn	44,750	3,680	9.38	--
100 acres of sprayed Bt corn	44,500	3,336	8.51	--

a] Table shortened by Texas A&M to exclude the 20% refuge data. SWCB is a major pest in these two areas.

b] Relative to 100% unsprayed non-Bt corn

c] Relative to 100% unsprayed Bt corn

The bottom line is that net returns for standing yields were 3.85% lower in a 40% (sprayed) refuge system than in a 100% Bt corn system. In terms of total yield, a 40% sprayed refuge system netted only 2.75% less than a 100% Bt corn system. Of course we could expect a 50% non-Bt refuge to be a bit more expensive. Extrapolating from data in the Kansas paper would give a net return estimate for 50% refuge of 4.81% and 3.44% decrease as compared to 100% Bt corn (no refuge) for standing yield and total yield, respectively. The Kansas study seems to provide comfort to those who think they will lose a lot of money by planting a 50% refuge of non-Bt corn. Inclusion of a refuge still makes more money than planting non-Bt corn and either spraying or not spraying it.

The full Kansas study can be found at http://www.oznet.ksu.edu/ex_swao/Entomology/Bt_Folder/btecfd.pdf. Readers who want to know more about Bt corn can also find the new Texas A&M publication, "Bt Corn Technology in Texas: A Practical View" on our website (http://agpublications.tamu.edu/pubs/eentom/b6090.pdf). EA-IPMs Greg Cronholm, Johnna Patterson, Cherinell Riley, and Dr. Greta Schuster (with West Texas A&M University), Brad Lewis (New Mexico State University) and I conducted Bt corn trials last year in several locations. The results are available here (http://lubbock.tamu.edu/Lubbock/ipm/AgWeb/r_and_d/corn/1999/Castro/99BtCorn.htm). All Bt corn performed extremely well as compared to non-Bt corn. RPP

Thrips infestations are currently at low to moderate levels in most local fields. These increases and decreases in infestation levels are something that we will be seeing almost all year long, but it appears that this most recent episode could be linked with the weather. Thrips feed in the terminal leaf clusters between the folds of the young leaflets. The damage they cause is dwarfing and malformation of the leaves. This type of injury normally occurs during the first month after plant emergence. Now, as mentioned in the previous newsletter, it has been well documented in other peanut growing regions of Texas that thrips feeding damage does not significantly effect yields or grades. I have personally seen many fields with damage, which quite frankly looked pretty ugly, but those twisted curled leaflets were still doing their job of making food for the plant. In fact, the plants were not hurt when the damage was severe enough to cause leaflets to turn black or wither. Young peanut plants (35 days or less) have repeatedly been shown to tolerate over 75% defoliation without yield reduction or delay in maturity.

Southern Blight (SB) has been found on a few plants within the region this past week in fields with inadequate crop rotation programs. The infection loci have primarily been restricted to the underground plant parts, such as the roots and crown. While I have not seen any surface activity (vegetative growth) I do find this to be highly unusual. If the nighttime temperature exceeds the upper 70's we could see SB within the coming weeks, so please keep an eye out for this destructive soilborne disease. CC

Corn earworm is present in ears of early sweet corn planted the second week in April in the South Plains Food Bank vegetable garden. Ears of sweet corn planted by the first week in April on the South Plains usually escape corn earworm damage.

West Texas A&M IPM program scouts report no potato psyllid larvae on potato plants in fields treated with Admire at planting. Potato psyllids were found in low numbers in untreated fields. Symptoms of psyllid yellows have not been seen in any potato fields during the week of June 5th.

By June 5th, a Severity Value of 28 was reached and P-Days totaled 331 in Springlake potato fields. The threshold P-Days for potato early blight is 300. Because daily rains have occurred in some fields and most potato plants are in the tuber set/tuber bulking phase, growers are advised to scout carefully and apply protective fungicides for early blight when lesions are identified on leaflets of lower petioles. When the potato late blight Severity Value exceeds 18, growers should initiate control measures if any late blight has been identified in the area or if weather conditions continue to favor late blight. Data obtained by continuous monitoring of temperature, rainfall and relative humidity in Springlake area potato fields is being integrated by the WISDOM IPM potato program to determine Severity Values and P-Days for potato disease management. RR

Weekly Overview

Incessant winds, which have been common across the region, subsided late Wednesday. With the exceptions of perhaps only a couple of days during rainfall events, winds have been a serious challenge for producers faced with the closing window for over-the-top applications of Roundup on Roundup Ready cotton acres. This technological bottleneck is very hard to deal with in the High Plains when winds are gusty for days at a time. Perhaps the recent reduction in wind velocity will allow growers to get the required Roundup treatments out on younger cotton in a timely manner. We have recently heard that some complaints have been filed with TDA concerning Roundup drift on other crops, particularly sorghum grown for seed production. It is important that one consider what is downwind from a field where an application is planned. Please refer to last week’s newsletter for information on spray nozzle selection and drift control comments.

Large storms with hail and damaging winds formed up and rolled across the central High Plains last Sunday night affecting several thousand cotton acres (overturned pivot picture). Kerry Siders (IPM Agent) reported that up to 9,000 acres were lost in Hockley County, with a still undetermined amount lost in Cochran County. The storm that pounded eastern Hockley marched across west central Lubbock County and affected several thousand acres there. Some cotton was also lost in the Buffalo Springs Lake area east of Lubbock. I suspect that over the last week around 20,000 acres across the region were either destroyed or severely damaged. High winds following the rainfall also resulted in blowing sand damage in many fields too wet to sandfight.

Rainfall was spotty and amounts varied from a few tenths at some locations. More significant amounts obtained at the "official" recording stations from the 9^th through the 11^th included: Lubbock ~1.76 inches, Littlefield ~1 inch, Plainview ~1.1, Lamesa ~ 0.3. Some areas did obtain higher or lower amounts away from the "official" recording sites. It appears that much of the dryland acreage is still struggling with badly needed rainfall. As for seasonal heat unit accumulation since May 1, all areas are significantly above long term averages (Halfway: +21%, Lubbock: +31%, Lamesa: +26%). Cooler temperatures at this writing have resulted in lower than normal heat units for several days this week. Average heat units accumulation per day at Lubbock is about 17, and during the cool spell we averaged about 12-15 per day. 

Assessing Stand Damage from Weather Events

When making replant decisions, the first rule is to not make the final judgement on the extent of damage to the crop too quickly (picture of cotton stand). Cotton has a tremendous capacity to recover from adversities. It is usually best to delay the final stand evaluation until after the crop is exposed to 2 or 3 days of good growing conditions. In the meantime, it is important to protect the crop from further damage with timely tillage operations. Tilling crusted fields will minimize wind and sand damage, improve aeration, and hasten warming and drying of the soil that in turn will slow development of seedling disease populations.

To determine remaining plant populations, count the number of plants that are showing signs of recovery in a predetermined length of row (i.e. 50 feet). Periodically, dig up the plants in a 3 to 5 foot section of row and critically examine the root systems, stems and terminals to insure the plants are capable of recovery. Make several stand counts at random locations in the field. In addition to plant numbers, make note of the number and length of skips in the rows being counted. Also, indicate the locations within the field where the counts were made. Sometimes, replanting may be necessary only in part of a field. Based on data reported by Dr. Levon Ray (retired Experiment Station cotton breeder), if 2 or more reasonably healthy plants remain per row-foot in 40 inch rows and long skips are not encountered, the stand is probably adequate for optimum lint production (Figure 1). Once populations drop below 1.5 plants per row-foot, then lint yields decline rapidly in a linear fashion. Our experience at AGCARES last year confirmed this (Figure 2).

Plant spacing uniformity is a critical consideration in replant decisions. Poor spacing uniformity, or skips, may cause significant yield reductions even though the average number of plants per acre is adequate for optimum production. Supak and Wanjura found that skips which decreased stands by 26 and 45%, respectively, lowered yields by 13 and 26%, respectively, even though final plant densities were in excess of 2 plants per foot of row (Table 4).

Table 4. The effects of skippy stands on cotton yields on the Texas High Plains, 1981-1984*.

The rate and extent of crop recovery will be largely dependent on the level of damage to the stems and leaves. Plants cut-off below the cotyledonary nodes will not survive. Likewise, those with deep stem bruises may eventually die or only partially recover. Plants that lost terminals may survive if viable buds remain on the plant and the portion of the stem below these buds is intact. Plants that are essentially defoliated can survive if stem damage is minimal. Any remaining viable leaf tissue (whole leaves, portions of damaged leaves) will increase chances for survival and hasten recovery of plants with intact stems.

Early season defoliation of young cotton seedlings can have a profound effect on crop yield potential. Severity of defoliation and crop recovery are important factors to consider. A summary of two years (1996 and 1997) of unpublished data from a seedling defoliation experiment conducted by Dr. Don Wanjura, USDA-ARS agricultural engineer in Lubbock is reported below. I think this data may be pertinent to the decision making process for some environmentally damaged fields. The treatments used in the study included 1) control, 2) removal of one cotyledon, 3) removal of both cotyledons, 4) removal of all true leaves, 5) removal of one cotyledon and all true leaves, and 6) removal of both cotyledons and all true leaves. The leaf removal technique employed mimicked leaf loss, but not stem and/or terminal bud damage.

The way I see it, it is a best case scenario for only defoliation effects since other potential yield loss effects such as poor stand, root health, stem damage (and subsequent potential for break-over after the boll load gets established), terminal loss, etc., are not included.

In 1996, Paymaster HS26 was planted on May 20 at 65,000 seeds/acre (about 16 lb/acre) (Table 5). Defoliation treatments were imposed on June 14, when cotton was 2.2 inches tall with 2.8 main stem nodes. Recovery data were collected on July 12. Plant survival from the most severe defoliation treatment (both cotyledons and all true leaves removed) was only 35% by July 12, whereas in the control treatment, survival was 95%. The first killing freeze was on October 22.

During the 1997 crop year, Paymaster HS26 was planted on May 16 at 58,000 seeds/acre (about 14 lb/acre) (Table 6). Defoliation treatments were imposed on June 11, when cotton was 2.8 inches tall with 2.3 main stem nodes. Recovery data were collected on July 11. Plant survival from the most severe defoliation treatment (both cotyledons and all true leaves removed) was only 28% by July 9, whereas in the control treatment, survival was 90%. The first killing freeze was on October 26.

1/ Wanjura and Upchurch unpublished data.

2/ Means within a column followed by same letter are not statistically different at the 0.05 probability level according to the Duncan’s New Multiple Range Test.

Differences in yield effects among treatments between the two years were attributed to differences in the amount of total water available to the crop. The 1996 growing season had nearly 25 inches of moisture available (rainfall plus irrigation), whereas the 1997 year had only 16 inches. These findings indicate that seasonal yield potential should be considered when making replant decision. Plant survival was reduced considerably by the most severe defoliation treatments.

Late Planting Considerations

Dr. John Gannaway (Lubbock TAES cotton breeder) has evaluated conventional variety performance under late-planted (mid-June) conditions at the Texas Agricultural Experiment Stations at Halfway and Lubbock. In general, short-season varieties have lower fiber quality (shorter, weaker), but produce higher lint yields than longer season types produced under short-season conditions. In short-season environments varieties such as Paymaster 183, AFD Rocket, All-Tex Express and All-Tex Quickie are generally expected to produce higher yields than other longer season types. However, a 3-year mean summary from Halfway and Lubbock for the years 1997, 1998, and 1999 indicates that Paymaster 2200RR yielded similarly to Paymaster 183. Fall heat unit accumulation in those seasons was certainly above average and benefited the longer season variety.

Fiber properties should also be factored in the decision process, as short-season varieties may have lower loan and market values due to shorter staple. Table 7 was generated based on crop value data from the Daily Price Estimation System (DPES) from the Texas Tech University (TTU) Agricultural and Applied Economics Department and the USDA Loan Schedule for the 1999 crop.

Table 7. Difference in lint production per acre required to compensate for staple length. 1/

The USDA loan data indicates that a variety with a staple of 32 would have to make 50 lb/acre more lint than a variety with a staple of 34 in order to produce the same gross value per acre. For the TTU DPES estimates of market value, the variety with a staple of 32 would have to have 28 lb/acre more lint than a variety with a staple of 34 to produce the same gross value per acre.

Seed availability of various varieties may be an issue, so growers should contact seed companies to determine other potential options. Closely monitoring fruit retention will be key to success of any late planted cotton crop in the High Plains. It is critical that outstanding square retention be the goal going into early bloom. Depending upon the location, the issue of fighting late season boll weevils also presents a serious hurdle for any late planted crop outside eradication zones.

Some questions have been asked concerning late planted ultra-narrow row cotton (UNRC) for irrigated fields. I am unaware of any research data incorporating UNRC vs. conventional 40-inch rows and planting dates. However, one should keep in mind that higher seeding and herbicide costs and other factors may be important. The theory behind UNRC would tend to support the concept, but management should be timely if implemented. Perhaps one could have more plants per acre which produce fewer bolls per plant in a shorter period of time than on conventional 40-inch rows. However, herbicide programs, irrigation, and harvesting all become a greater challenge. LEPA irrigation cannot be practiced using UNRC. An additional concern is protection of seedlings from blowing sand if planted relatively flat. Many successful UNRC growers implement some kind of cover system to protect seedlings from wind and sand damage and at this late date that appears to be a significant challenge. RB

For additional and more detailed information, visit the following links:

Effects of Stand Loss and Skips on Cotton Yields: http://soil-testing.tamu.edu/publications/800792-skips_ne.pdf

Making Replant Decisions: http://soil-testing.tamu.edu/publications/800824-replant_.pdf

Table 8. Data from the South Plains PET Network, June 7-13, 2000:

	Reference		Estimated Crop PET [a] in inches
	PET (inches)	Rain (inches)	Cotton		Sorghum		Corn
			Seedling	1st square	3-leaf	5-leaf	6-leaf	8-leaf
Lubbock	1.66	1.18	0.12	0.37	0.91	1.16	1.41	1.66
Lamesa	2.18	0.87	0.15	0.48	1.20	1.53	1.85	2.18
Halfway	1.85	0.56	0.13	0.41	1.02	1.30	1.57	1.85
Seminole [b]	2.49	3.70 [c]	0.17	0.55	1.37	1.74	2.12	2.49

[a] These PET estimates are based upon High Plains crop coefficients. PET will vary with growth stage, which is affected by cumulative growing degree days (heat units). 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

[b] Site is actually closer to Denver City.

[c] Probably an overestimate of actual rainfall amount. Problems with rain gauge this week.

PET data and weather data for Halfway, Lamesa, Lubbock, and Seminole 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.