Growing conditions have been excellent over the last week where moisture has been adequate. Much of the timely planted cotton crop has or is moving away from the Roundup application window. Heat unit accumulations are ahead of schedule but rain is needed as no area wide event has occurred for three weeks. Much of the dryland crop has failed. Concerns for economical irrigation and fertilization are developing and are addressed in this issue of FOCUS.

Cotton insects have been on a roll with heavy thrips infestations persisting but at least starting to wind down. Extensive damage has occurred where inadequate thrips control was exercised. Late planted cotton should be relatively safe. Fleahoppers and some western tarnished plant bugs are moving into some of our squaring fields and in some instances requiring treatment. The absence of rains for most of June is encouraging these pests to move out of alternate hosts. Expect problems to escalate through June and into July. Beet armyworm infestations have persisted in many fields across the area through continual egg lay but very low survival. So far, very few fields have been threatened either with excessive stand loss or square loss. Boll weevil numbers remain low as the last of the overwintering weevils emerge and enter squaring cotton fields. Nevertheless, there have been fields requiring 1-2 sprays. False chinch bug problems continue but appear to be starting to wind down.

Corn has really taken off with this week's hot conditions. Blooming sunflower fields have sunflower moth problems and need to be monitored and sprayed where warranted. False chinch bugs continue to pose a threat to small corn and sorghum plants.

Most fields have at least emerged to a stand. Many other earlier surviving fields have several squares and a few may not be far from first flower. Pest problems will range from thrips in the later planted fields to beet armyworms, bollworms, boll weevils, western tarnished plant bugs and cotton fleahoppers in the earlier planted fields.

Table 1. Thrips Control Test - North of Earth, Texas. 2001. 1/

 The thrips test east of Amherst (Table 2) was planted later and has had much less thrips pressure than the Earth test. I predict that yield loss will be less than 6% in the untreated check. This still could represent about 70 pounds of lint, more than enough to pay for any thrips control and provide a tidy profit. All treatments in this test had low thrips numbers and a lower percentage of immatures with the exception of the untreated check, Adage seed treatment, Gaucho seed treatment and the Roundup application window-timed Orthene foliar treatment (just treated after the June 20 counts). This test was just past three weeks from planting.

 Table 2. Thrips Control Test -- West of Amherst, Texas. Randy Bales. 2001 1/

I am bothered by the higher number of thrips in some fields that are into the early stage of squaring. This is not a typical situation and I do not have any management experience for these situations. We normally do not treat for thrips past the 5^th true leaf. In a year with depressed cotton prices, I probably would still follow this advice. After all, we will probably have plenty of opportunities to treat later pest situations. There is no sense in blowing all your money now.

I am also bothered by the number of fields I have seen where thrips were not handled correctly. Too many producers still believe that thrips are a cosmetic problem that may take some earliness away. The bottom line of my research program is that thrips are one of our most serious yield reducing pests. Unfortunately, many producers don't get too concerned unless cotton is very visibly damaged, especially with lots of boll feeding.

If you can provide sufficient water and fertilizer to set and maintain a good crop to harvest, then it is important to save these early squares. If you can't provide this care, then you are wasting your money on protecting fruit that will be shed later on due to other stress factors. There really isn't any reason for small squares to be shed unless an insect is damaging them, or wind, blowing sand or tractor blight are the cause. I want to see at least 90% of the first week's squares retained, 85% of the first two week's squares retained and 75% of the first three week's squares retained. Since square set can drop quickly for no apparent reason, it behooves you to scout frequently.

We are seeing larger numbers of fleahoppers in early squaring cotton than we are used to. Our fleahopper number threshold is about 25 fleahoppers per 100 plants inspected. This is based on the premise that it will take reproduction to recruit enough numbers to economically damage our cotton crop. This usually does not develop until toward the end of the second week of squaring. But we are beginning to see fields this year that are getting into trouble during the first week of squaring. This is a common occurrence in the Blacklands, where extensive weed host reservoirs develop large numbers of fleahoppers that eventually move into cotton as it begins to square. They use a threshold of 15 fleahoppers per 100 plants. With all the weed hosts that were generated by winter and spring rains, and the wholesale drying up of these hosts due to the lack of rains in recent weeks, producers should expect higher levels of fleahopper activity in their fields.

While some fields in the area are already in trouble due to heavy fleahopper infestations, many other squaring fields have very few of this pest. This disparity is probably due to the presence (or absence) of adjacent weed hosts such as silverleaf nightshade, lanceleaf sage and primroses. There are other hosts as well. I would suggest scouting every 3-4 days as fields begin to square. This pest is difficult to scout for and assessment of square damage can be challenging.

While adults are a big 1/8^th inch long, immatures (or nymphs) start out less than 1/16^th inch long. These nymphs can be almost clear in color and blend in with aphids and thrips infestations. Adults readily fly away when disturbed, especially if you cast your shadow across their plant. Nymphs can run down the cotton stalk to the ground or hide in the terminal whorl. In any case, finding these little square thieves is a challenge. To make matters worse---damaged squares may not show symptoms for 2-3 days after being fed upon. It is not uncommon to record 85% square set going into the second week of squaring, only to come back in a few days to discover square set has plummeted to 50-60%. My recommendation? Scout often and carefully.

There are many good insecticides for fleahopper control. Please consult our guide (LINK) for details. These include Orthene and Address, Lorsban, Bidrin, various dimethoate products, Provado, Steward, Lannate, Vydate, methyl parathion and Metasystox-R. Don't skimp on rates, especially if western tarnished plant bugs (WTPB) are present. These are much harder to kill. While a single application usually will do the job, heavier, chronic infestations may require multiple, frequent applications. Don’t delay an application either. Also, boll weevil applications of Vydate will handle fleahoppers but not WTPB (boll weevil rate is too low).

WTPB is a larger insect than a fleahopper with the adult reaching ¼ inch in size (see pictures). This bug is very mobile and can readily move into and out of a field overnight. Don't be surprised if you find lots of WTPB damage (pictures) but very few pests. But later, eggs will hatch and a large flush of nymphs will appear. Use higher rates of most insecticides to kill this tough pest. You might have to resort to pyrethroids if large migrations occur from adjacent host plants. An example of a rate increase would be for Vydate CL-V where 8.5 oz per acre is sufficient for fleahoppers but 12.7 to 34.0 oz may be needed for WTPB.

There is another bug out there that can cause some confusion when identifying fleahoppers. This is a scentless plant bug (picture). It is in a different family (Coreidae, subfamily Rhopalinae) than the fleahopper (Lygaeidae). Look at the antennae -- quite different compared to the fleahopper. This insect can appear in fairly high numbers mixed in with fleahoppers but they do not appear to concentrate on squares and therefore do not appear to adversely impact square retention.

Egg masses continue to be found as well as very small larvae, especially in fields from Lubbock, north. These northern infestations are unusual for this time of year. Trap catches by the Texas Boll Weevil Eradication Foundation are still up compared to this time last year. In fact they are running 4.3 times higher than last year in west Texas while only 27.6% higher in the south Texas/Winter Garden eradication zone. I believe the BAW threat should be taken seriously and have advised the Foundation to do so too.

Boll weevils continue to emerge at much lower levels than last year. Our GRID trapping program with Plains Cotton Growers, Inc. not only shows this but also the dramatic impact last year’s eradication activities had in the active zones (LINK). In spite of lower numbers, there are still some hot spots developing across the area outside of active eradication zones. These fields are far fewer than in previous years and trap numbers are generally tending to be on the lower side. Still, some fields have required two applications based on trap numbers. I hope producers that need to treat these hot spot fields are not trying to economize by not spraying. Good cotton growing weather could increase these lower weevil numbers into big problems by August, a month before Foundation diapause sprays are to begin.

The TBWEF will be using lower trap triggers this year in an effort to close the door on our boll weevil problem a little earlier. This lowering of trap triggers was made possible through the combined results of a very successful program last year and high winter mortality. The only danger of this approach is if it increases the percentage of fields treated in an area to a level where beet armyworm natural enemies are broadly impacted and BAW are increased accordingly. Since there is a threat of more BAW activity this year, the Boll Weevil Technical Advisory Committee recommended that the TBWEF keep the percentage of sprayed acreage in a given work unit each week at or below 10% if there is a documented threat of beet armyworm problems.

The TBWEF is also asking producers with damaged cotton that will not be taken to yield, to destroy plants in these fields to remove a food source for boll weevil feeding. This also applies to fields that will be planted to another crop such as sorghum. Please don’t create situations where cotton is growing in fields with other crops.

While their numbers are down considerably in most instances, FCB numbers can still be found in some areas where the ground is literally "moving". But the main concern now will turn to the possible impact of fewer numbers of this pest on squaring cotton. And I will tell you again for the second week in a row---we have not observed significant square impact from numbers ranging up to 10-15 per plant. This does not mean that I am saying that FCB will not reduce square set. I would certainly watch infested fields very carefully, and frequently.

Natural enemy levels still look good in most untreated fields. Crab spiders are the dominant one, often averaging one per plant. I consider crab spiders the top contender as a fleahopper predator. Great as an ambusher. Fleahoppers are tough critters to chase down. I am also noticing more damsel bugs than last week, another good sign. JFL

Sunflower fields are well into bloom or just starting. We are finding sunflower moths in these fields, and as mentioned last week [LINK], it is important to time spraying to 20 percent bloom (or 5 percent bloom in practical terms - see the photo of percent bloom (picture). However, some fields are not blooming uniformly, and timing questions might arise. Spray at 20 percent bloom for the early blooming plants. Expect Warrior insecticide to last 6 days for a light infestation and 5 days for heavier infestations. Expect to respray on the sixth or seventh day, depending on infestation levels. Assuming another 6 days of efficacy from the second application, plants will have been protected for 13 days of the bloom period.

Our Sunflower Insect Pest Guide (http://lubbock.tamu.edu/ipm/AgWeb/sunflower/docs/b1488.pdf) lists Furadan; Sevin; Lorsban; Bacillus thuringiensis insecticides; endosulfan; methyl parathion; and the pyrethroids Baythroid, Asana, Karate, and Scout X-TRA for control of sunflower moth larvae. Note that Karate is no longer labeled for sunflower, but Warrior is labeled and has the same active ingredient.

Research on Transgenic Corn for Rootworm Control. Monsanto is preparing to introduce transgenic corn that will control corn rootworm larvae and potentially eliminate the need for a rootworm insecticide. This corn could possibly be available to growers in time for the 2002 crop year, but several EPA hurdles must still be crossed. Additionally, Dow and Mycogen are preparing to introduce their own rootworm-active corn, but commercial availability appears to be a year or so behind Monsanto's corn.

These new transgenics show a lot of promise. According to Midwestern research data, both companies have produced hybrids that perform as well or better than soil-applied insecticides in most trials. With funding from the Texas Corn Producers Board, we are testing the efficacy of the Monsanto transgenic hybrids in Texas and New Mexico. Extension Entomologist Roy Parker has a trial in south Texas. Carl Patrick, Extension Entomologist in Amarillo, Robert Bowling, Extension IPM Agent in Moore County, and Greta Schuster, Professor at West Texas A&M have another large trial in the northern Panhandle. Finally, Brad Lewis (New Mexico State University) and I have two trials in New Mexico. I have been vague as to the exact locations of the trials in order to reduce the risk of sabotage by anti GMO groups. Private farms are cooperating in these trials. We will have data to report in FOCUS by early August.

If you would like a copy of the final research report, please send an e-mail to me
(p-porter@tamu.edu). I will send the report sometime in October after the Texas Corn Producers Board approves it.

The growing conditions over the past week have generally been excellent. Most of the irrigated crop is moving along very well. The PET network has indicated that we have averaged about 0.35 inches per day of reference ET, while heat unit accumulation has ranged from 17-20 at Halfway, 18-21 at Lubbock, and 19-20 at Lamesa. This places the percentage of long-term average from May 1 through June 20 at 8, 20, and 20 percent above normal for Halfway, Lubbock, and Lamesa, respectively (graph). We will have blooming cotton in the region in a few more days, and some late April and early May planted cotton blooming by the end of the month. It appears that we have considerable dryland cotton acreage headed for the insurance adjuster, as no significant rainfall has occurred across most of the largely dryland production region during June. We will have more on this next week.  

Irrigation Concerns. With the hot, dry, and windy conditions across the region, producers have many questions concerning irrigation. Many producers are indicating that they only have a certain amount of financial resources for irrigation because of significantly higher pumping costs this year. Getting the most benefit from those irrigation dollars will depend greatly upon future rainfall amounts and distribution. If we head into another 2000 type year with a fairly good crop going into July and August and get no help from mother nature, then we will have a very tough situation. However, if we can get some good rainfall amounts and distribution in July and August, producers will need to try to keep the crop moving along. Thanks to the rainfall obtained through early April and good growing conditions in many areas, many fields are continuing to "root down" in a good manner. However, once squaring begins and through the early fruiting phase, moisture stress should be kept relatively low in order to keep the yield potential present in case good rainfall amounts and distribution occur. For our region, about 80% of the potential yield is on the plant as it gets into the early bloom stage.

Generally speaking, we can expect about 50 lb of lint production per acre-inch of stored soil moisture plus rainfall and LEPA irrigation. The High Plains Underground Water District Web site has some very good data from multiple crop years (http://www.hpwd.com/programs/pet/pet.asp). The range across sites and years reported was from 25 to 90 lb of lint production per acre-inch of available water.

With furrow irrigation, only one summer watering may be justifiable in the Texas High Plains whereas two or three waterings may be needed in a longer growing season. As a general rule, cotton that is being watered twice during the summer produces most efficiently when the first irrigation is applied when first squares are 2 to 3 weeks old (near bloom initiation) with the second 2 to 3 weeks later. Cotton that is to be watered more than twice during the summer is generally most productive when irrigated at 14- to 20-day intervals beginning when first squares are 2 to 3 weeks old or when warranted by early season stress development (see graphs of Irrigation Timing here - graph 1, graph 2, graph 3, graph 4).

For pivots utilizing low elevation spray systems, it will be important to apply at least 1 inch every 7 days in order to get even a "minimum" amount of water into the soil. This amount can be applied using a system with about 3 gpm per acre. If environmental conditions are such that temperatures of 100 degrees, high winds, and low relative humidity are encountered, evapotranspiration values of up to 0.5 inch/day may be obtained.

Research has shown that the LEPA (Low Energy Precision Application) irrigation system (circle farmed, with applications in alternate and diked furrows, dragging socks) will make water go much further than spray-type systems. Jim Bordovsky, Experiment Station Irrigation Engineer at Halfway has provided some useful information, which is detailed below. With LEPA, a more frequent irrigation interval following bloom (such as a revolution every 2 days) generally tends to increase yields when compared to intervals of lower frequency if one has a reduced amount of irrigation water available. Cotton responds very well to high-frequency deficit irrigation, even at amounts as low as 0.20 - 0.25 inches applied every 2 days. This amount of water could be applied using high-frequency LEPA center pivot irrigation with wells delivering a total of 2 gpm per acre or about 240 gpm per 120 acre pivot.

Results from Experiment Station cotton research conducted at Halfway indicate that when LEPA irrigation capacities are limited (that is 0.1 inch per day, or 2 gpm/acre, or 240 gpm per 120 acre pivot), a 2-day frequency was best (Table 3). When irrigation capacities were above 0.2 inch per day, frequency was not as critical.

Table 3. Cotton lint yield using LEPA irrigation at three irrigation capacities and three frequencies of application, Halfway, TX (1995-1997).

Efficiencies of in-canopy low pressure spray treatment versus LEPA systems have been documented at the AGCARES facility at Lamesa over the last few years. Over a 4-year period (1990, 1991, 1993, and 1994), LEPA produced an average of 116 lb/acre more lint than the in-canopy spray system using comparable amounts of water. In one dry season (1994) when the dryland treatment produced only 46 lb/acre of lint, LEPA out-yielded the spray treatment by up to 490 lb/acre (Table 4).

 Table 4. Comparison of LEPA and spray irrigated cotton yields at AGCARES, Lamesa, TX (1994).

For a grower's guide to PET use and other information go to: http://texaset.tamu.edu/growers.php

Table 5 provides various irrigation capacities and their ability to provide water to a cotton crop when water use is an average of 0.24 inches per day.

Table 5. Limited cotton irrigation for a 1/4 mile center pivot on 120 acres.

 N Fertilization Considerations for Cotton. Nitrogen fertilization should be considered in irrigated fields making good progress. Figure 1 (link to figure) shows a typical N uptake curve for cotton and corresponding crop development stages. Suggestions for applications of approximate percentages of total N are also shown. A one-bale cotton crop will actually remove about 45 lb of actual N per acre, but due to inefficiencies in uptake and in the soil, about 50-60 lb N/acre are actually required. Generally speaking, about 30-50 pounds of actual N per acre are adequate for dryland cotton. The higher rates should be definitely considered if the yield potential (stored soil moisture) is adequate for higher lint yields. Sidedressing and/or topdressing should be completed before blooming, with extreme care taken not to prune roots during the application. Benefits from low rates of foliar-applied fertilizers are questionable. Fertigation is a practice that is gaining in popularity in the High Plains. Where possible, nitrogen fertilizer (UAN, 32-0-0) can be applied through center pivots or "fertigated". This results in lower application costs. One should consider whether a LEPA system with drop hoses is used vs. a spray system. If a pivot rigged with spray nozzles has marginal water quality and extremely hot, dry conditions are encountered, then some salt burn may be encountered on foliage. This type of N management fertigation scenario has been used and validated for the last several years at the Lamesa AGCARES facility using alternate furrow LEPA irrigation. To obtain maximum utilization of applied N, the total amount of N should probably be applied prior to peak bloom, in order to compensate for the "lag time" associated with application, bacterial conversion of urea and ammonium forms to nitrate-N, and physiological uptake delays. It is important to not over fertilize with N if reduced yield potential is anticipated. This is due to the fact that it makes late cotton more difficult to manage on the backside of the season. Some late-season insect problems, such as aphids, can be aggravated by high N status plants. RB

As crops approach their peak water use periods, this is a time to look at soil moisture storage capacity to help meet the coming high water demand, particularly where irrigation system capacity is limited. A discussion of soil moisture monitoring and crop rooting depth potential was included in the July 21, 2000 issue of FOCUS on Entomology (see http://lubbock.tamu.edu/ipm/AgWeb/newsletters/focus2K/july_21/frameset.html .) DP

Crop water use estimates (inches per week) for the week of June 14-20, 2001.

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