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Volume XV no. 13 September 7, 2001
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IN THIS ISSUE: Last Issue of FOCUS for 2001 Season Cotton Insects
Sorghum Insects Cotton Agronomy
Wheat Agronomy
Cooler temperatures have become more the norm for the High Plains as fall settles in. As a consequence, daily heat unit accumulations have declined from about 20 to 10-15. These lower heat unit accumulations will slow everything down for cotton. Substantial rainfall has been received in some areas while the region as a whole is still running behind our long-term average for the year. These rains have helped some irrigated fields while causing regrowth problems with other limited irrigation and dryland fields. Insect problems are all over unless you have a defoliation problem with a late field from Lubbock south. This would involve things like loopers, beet armyworms and spider mites. The boll weevil eradication program kicked off in the remaining two zones, Northern High Plains and Southern High Plains. By the time we have a plant killing frost we should be able to see dramatic reductions in trap catches of weevils due to the spray activities of this program. With the focus away from irrigation and insect management, it is now time to consider harvest aid options for cotton. A complete discussion is provided in this issue. We are also observing European corn borer activity in grain sorghum, normally concentrated in corn. More than likely it is not advisable to treat these infestations. Planting wheat is now on the minds of many producers. Dr. Calvin Trostle provides some more insights this week into wheat planting and management decisions for wheat grown primarily for grain. 
This is the last issue of this newsletter for the 2001 season---- for a good reason----there should be no more concerns remaining pertaining to pest problems. Any boll that has half a chance of making it to the gin is already safe from bollworms, beet armyworms, aphids, plant bugs and boll weevils. The approximate insecticide use cutoff dates for a northern location like Dimmitt or Tulia would be August 18 for boll weevils and plant bugs, August 22 for bollworms and September 1 for defoliators. Comparable cutoff dates for areas at the level of Lubbock would be August 27, September 3 and September 16. Southern areas such as around Lamesa would be September 2, 10 and 23. These dates are based on last boll making dates (with only a 50% probability) of August 1 for Dimmitt, August 10 for Lubbock and August 15 for Lamesa. These dates take into account the warmer fall weather we have been experiencing the last 5 years. Aphids or whiteflies could still rear their ugly heads and produce numbers sufficient to generate honeydew deposits and sticky cotton. Based on past experiences and the status of our current pest levels, I would say this would be extremely doubtful. So all that remains for this year is to complete the sprays for boll weevil eradication and get the crop out of the field in a timely manner to avoid weathering losses. This has been a very unusual year from my perspective, not because of any one event but more because of several events. Because of the depressed economics of cotton this year and anticipated higher costs for pumping irrigation water, producers looked everywhere for ways of cutting back inputs. The first insect management tactic to reach the chopping block was thrips control, especially at-planting insecticides such as Temik. This turned out to be a big mistake as thrips numbers were high and persistent. In fact, thrips will end up the number one yield detractor for the 2001 season in the High Plains. I still maintain that for irrigated cotton, the greatest insect management return for your dollars is for thrips control, at least over the long haul. Emilio Nino, IPM agent in Dimmitt, and I did conduct two thrips control tests this year and will provide final reports to you through this web site. Hopefully these test results will help you make informed thrips management decisions for 2002. I was concerned about the possibility of increased cotton fleahopper and plant bug problems this year because of the abundant winter and early spring rains. When the weather later turned hot and dry, I really thought we were in for it. As it turned out, fleahoppers were a minor pest this year while plant bugs did not develop into much of a problem until later in the year. What did appear were false chinch bugs. These guys were in seedling cotton in high numbers in many fields but were generally restricted to smaller portions of each infested field. When enough numbers are feeding on a seedling plant, they can cause plant death through desiccation. As plants grew and began to square, many consultants and producers were concerned about square retention when these bugs congregated beneath bracts of squares in numbers approaching 50/100. As in past years, we never could document any square loss due to these infestations. False chinch bugs remained in cotton in some instances to the present time although many moved to sorghum as heads were exerted. Under the funding assistance of Cotton Incorporated, IPM agents Tommy Doederlein and Brant Baugh, Cotton Specialist Randy Boman and I initiated a COTMAN test at AgCares. The objective of this study was to investigate different pre-bloom square retention levels and subsequent compensation ability with two planting dates. We need this information if we are to more competently manage both fleahoppers and early Lygus infestations. The results of this test will be made available to interested parties sometime in January, 2002. Beet armyworms were another pest that appeared early and posed a threat to our cotton growing region. High numbers were found in seedling cotton, predominantly in the northwest area of the High Plains. This was an area where high numbers persisted late in the season last year. Apparently, many of these beet armyworms survived the winter to emerge this year. With the droughty conditions we were experiencing, we all thought we were in for big trouble. Once again the early, high numbers of beneficial insects and spiders appeared to keep these early infestations in check.Early season boll weevil numbers were way down based on early GRID trap catches and trap catches of the Texas Boll Weevil Eradication Foundation (TBWEF). This was actually expected since our dig-up cage studies and survey of overwintering site litter indicated that lower numbers of weevils had entered overwintering sites and survival of those that did was very low. In fact, boll weevil numbers during the early season period were probably at their lowest level since 1995. The TBWEF program in the three active zones had also done an excellent job of lowering numbers in last year's program efforts. Because of the lower numbers of boll weevil present this year, less acreage needed to be sprayed by either producers or the Foundation, resulting in excellent preservation of beneficial insects and spiders and no subsequent secondary pest outbreaks. The two new zones started diapause applications on September 3 with the great advantage of having much lower numbers of weevils to contend with at the start of their program of any other eradication program has in the history of eradication programs in the country. Next year's boll weevils should be even less than a problem. The bottom line is that producers in the High Plains no longer need to concern themselves with boll weevil management decisions ever again. The Foundation has that responsibility now. For the second year in a row, bollworm problems were few and far between. Even when their numbers passed the economic threshold they generally were at lower levels than a more typical year. Reduced corn acreage, Bt corn and less spraying for other pests may be the most likely factors causing this decline in pest status. Cotton aphids were strangely quiet this year. While most fields had a few early on, they all failed to develop into problem numbers. In fact, we were unable to establish an insecticide screening trial for aphids this year. Abundant beneficial insects were certainly helpful in keeping aphids in check, but something else was missing that would have precipitated an outbreak?Banded-winged whiteflies probably took top honors for the most unusual pest problem this year. In many cases it appeared that adjacent sunflower fields were responsible for generating the large numbers of adults that subsequently moved to and reproduced in cotton fields. IPM agents Brant Baugh and Scott Russell cooperated in conducting two insecticide screening trials against this pest. We weren't overly impressed with any of the treatments but several did a fair job of control. A complete report will be available later. I believe very few fields were ever sprayed for this pest. There is no research-based treatment level for banded-winged whiteflies so we were only estimating what might be a starting level for treatment decisions. I really don't think anyone got hurt by this pest this year and certainly hope that it will not return as a pest problem next year. Plant bugs became a problem in several fields as the season unfolded, especially in August. While infestations were not as intense and damage was less than that observed in 1999, infestations were more widespread. We are definitely going to have to come to grips with this pest if it is to continue to expand in scope and importance. There are a number of studies underway both here and in other parts of the country. Hopefully some answers will be forthcoming.Last but not least, I have already mentioned the abundance of beneficial insects and spiders this year and the role they played in helping us with potential pest problems. The most common predators were crab spiders, damsel bugs, big-eyed bugs and minute pirate bugs. Since aphid numbers were exceedingly low, lady beetles were also low in number. JFL
Steve Davis, IPM Agent in Crosby and Floyd counties, is finding European corn borer (ECB) larvae in as many as 10 percent of plants in some fields. He is also finding some lodging, but most of this is due to stalk rot, not the corn borers. As we mentioned last week, there is a third generation flight of ECB moths going on, and since there is no good corn to lay eggs on, sorghum is now an item of interest. The larvae will enter the stalks, but will not girdle them. Insecticide use is not economically justified for this pest. Continue to scout for headworms. PP
Current situation. Considerably cooler temperatures have been encountered over the last few days. Daily heat unit accumulation for the last 3 days has averaged about 11 at Halfway, 13 at Lubbock, and 14 at Lamesa. We are now at a seasonal total (from May 1) of 2050, 2317, and 2460 for Halfway, Lubbock, and Lamesa, respectively. This is about 15 percent above normal for the season. Rainfall has been obtained in some areas. However, at this late date, only the irrigated fields that were pushed will receive much of a benefit. We are beginning to see some new growth in some irrigated fields in which irrigation was terminated in mid- to late August. These may be a challenge to condition for harvest. For those still wondering about irrigation termination go to this link.
2001 High Plains Harvest Aid Guide. The new model of the harvest aid guide is now available. Average High Plains harvest aid prices are also available. You can view a brief overview of recent changes in harvest aid products and new products here. We will be working on getting several harvest aid trials established over the next week or so. We will get the word out on what is and isn't working on the various types of cotton we have out there this year. If anyone has any comments concerning specific products or tank mixes, please call and share those.
To terminate or not to terminate? When considering potential impacts of adverse weather conditions, many producers view harvest aid application as a means to reduce overall economic risk. However, with all of the money spent on producing this year's crop, the additional expense of harvest aid applications may not make financial sense to some. The yield potential of the crop must of course be factored in, but we also need to look at the calendar and see where we are at this stage of the game. First, we have many fields that are finishing up early this year. If we take the National Weather Service's word for it (at least based on long-term averages), then Table 1 is worth checking out: Table 1. Average first freeze date for various High Plains locations. 1/
1/ From Public Information Statement, October 14, 1998, National Weather Service, Lubbock, TX. If we take Lubbock as an example, we would expect the first freeze around October 31. With the early crop we have this year, this implies that we would have a crop opening up early sitting in the field undergoing at least some weathering. If cotton reaches a high percentage of open bolls in early- to mid-September, then it could possibly experience 6 weeks (or more) of weathering. Last year, we did not have a killing freeze at Lubbock until around November 7. The highest quality that a boll has is when it first opens, and from that point on, lint and seed quality deteriorates. Weight also decreases with time of exposure. Weathering losses are hard to determine, but the following information may be worth reading: Dr. Levon Ray (Experiment Station cotton breeder prior to Dr. John Gannaway) and E. B. Minton conducted a 3-year trial in the late 60's and early 70's which investigated the effects of weathering on stormproof cotton at Lubbock. In this small-plot trial, hand harvests were initiated at 2-3 weeks AFTER the first killing freeze. Please note that harvest aid use was not as popular during that period of time. The losses reported here are relevant for after a freeze. However, this also implies that the losses prior to a freeze would NOT be included in these data. Therefore, I submit that actual losses due to field weathering are greater than those reported in the above paper because the weight losses prior to the killing freeze were not determined. The total precipitation during the harvesting period was 1.65 inches in 1969, 0.17 inch in 1970, and 1.32 inches in 1971. Since stormproof varieties were used, no preharvest losses (cotton falling onto the ground) were reported in the study.They concluded that rate of weight loss was greater in the early weeks of the harvesting season, based on regression analysis of the 3-year data set. Total weight losses of cotton lint were estimated at 3 percent the first week, 8 percent after 4 weeks, and 12 percent after 11 weeks. For 600 lb/acre cotton (their example), losses were estimated at 18, 48, and 72 lb/acre for weeks 1, 4, and 11, respectively. If we apply those same loss rates to varying yield levels, then the data in Table 2 are pertinent: Table 2. Potential yield and gross revenue losses due to field weathering. 1/
1/ Assumes 3%, 8%, and 12% yield potential loss due to weathering in weeks 1, 4, and 11, respectively. Assumes cotton price of $0.50/lb. The project also noted that fiber length was significantly reduced by field exposure. They concluded that 6-7 weeks of exposure would likely result in a 1/32 inch decrease in fiber length. Colorimeter readings of reflectance (or rd) were also detrimentally affected over time and were highly correlated with field weathering. This indicates that color grades have the potential for reduction over time. They concluded (using 1972 loan prices and their estimates of yield loss) that the combined weekly loss in terms of both yield and quality at the beginning of the harvest season would be about $9.50/acre for their 600 lb/acre yield. A separate economic study of the above mentioned data indicated that highest cotton prices were generally obtained earlier in the harvest season. Total gross returns are generally higher earlier in the season, and by the last week of January, severe reductions can usually be expected. 2000 Cotton Incorporated weathering project. Dr. Alan Brashears, harvest engineer with the USDA-ARS Gin Lab at Lubbock, cooperated with us on a Cotton Incorporated Texas State Support project last year. We utilized large plots, which were terminated with harvest aids. Some treatments were harvested in a timely manner in September and early October, and others were allowed to weather in the field. Harvest was conducted each month until the final harvest date in January. We were not able to detect statistically significant differences in lint yield across harvest dates in that project. However, USDA-AMS classing data from the commercially ginned project were obtained. First digit color values indicated that highest quality was obtained for September and early October harvests (1 and 2 values). First digit color was intermediate (3 and 4 values) for the October 20 harvest date, and with lowest quality for subsequent harvests in November and December (4 and 5 values). Second digit color of 1 dominated early harvests and by November 14, all plots had a 2 value. HVI reflectance values decreased with time. HVI +b was not significantly affected by harvest date. Staple length was reduced by field exposure over time by about one 32nd of an inch. Fiber strength was reduced by up to 2.5 g/tex as length of exposure increased. After mid-October precipitation, 50% of the bales had bark discounts. Later harvest dates resulted in bark discounts for 100% of the bales. Reduction in loan value amounted to about $0.08/lb lint when the optimum termination and harvest was compared to the November 14 harvest date. Lint exposure to 3.1 inches of precipitation resulted in losses of $38.88/bale. This work will be continued this year. Estimating lint yields. Dr. Will McCarty, Extension Cotton Specialist at Mississippi State University has developed an excellent publication on yield estimation. It has been available on the web for the last several years, but MSU has recently revamped their publications and now I can't find it. So I am providing his publication I saved from an early web site retrieval. Basically it says that it takes about 155,700 normal (High Plains average of 4.0 gm seed cotton/boll = 1.4 g lint assuming a lint percent for seedcotton of 35%) bolls to produce a 480 lb. bale of cotton. This is equivalent to about 325 bolls/lb of lint. For 40-inch rows this calculates to 11.9 bolls per row-ft for a one bale/acre yield (155,700 bolls/13,068 row-ft/acre for 40-inch rows). This is very close to the "one boll per inch = one bale per acre" number that many folks use to estimate yields in 40-inch rows. To help determine a "worst case scenario" I checked the report from our 1998 High Plains Cotton Survey we conducted for Plains Cotton Growers, Inc., which was submitted to FCIC and USDA-RMA. One of the worst locations (in terms of boll size and lint yield) was the Lamesa dryland replicated variety test site. It averaged about 480 bolls/lb of lint across several varieties. This implies that it would take about 230,500 bolls/acre of that size (about 2.7 gm seed cotton/boll) to produce a 480 lb. bale of cotton. This works out to about 17.6 bolls per row-ft for a one bale per acre yield. It is possible that the numbers could be worse, but I still think this may be a good number to use for a worst-case scenario. The highest number of bolls/lb of lint for dryland samples in the survey was just over 600. This translates to 288,000 bolls/bale, or 22 bolls/row-ft in 40-inch rows. RB
Wheat varieties for grain. In 2001, wheat variety trials were harvested from seven locations across the Texas Panhandle and northern South Plains. For a table of results contact your County Extension Agent as results are not available on the internet yet. The dryland trials were established near Silverton, Sunray, Perryton, and Canadian. Limited irrigation trials were located near Wellington and Wilderado, and a site near Dimmitt was fully irrigated. According to Brent Bean, Extension Agronomist at Amarillo, the varieties that yielded in the top 20% in the dryland trials were very consistent between locations. Top varieties were Jagger, TAM 105, Thunderbolt, 2174, Tonkawa, Cutter, and Dumas. Jagger is an early maturing Kansas wheat that has yielded particularly well the last couple of years. It is considered a good grazing wheat that can be planted deep and has good resistance to most diseases. TAM 105 has been around since the mid-70s but continues to perform well year in year out, despite the fact that it is susceptible to most diseases. Thunderbolt has been impressive since its release by AgriPro in 1998. Tonkawa is an Oklahoma wheat with a TAM 105 background that also has been a very consistent performer. In the fully irrigated trial near Dimmitt, several varieties yielded more than 100 bu/Acre. Commercial varieties yielding over 115 bu/Acre were Jagger, Prairie Red, Thunderbolt, TAM 201, and TAM 400. Prairie Red is essentially TAM 107 with Russian wheat aphid tolerance. TAM 201 has been tested for several years and generally performs best in the Rolling Plains area of Texas, but may be suitable for the South Plains. TAM 400 was developed as a south Texas wheat but has performed very well in irrigated trials in the Panhandle the last two years. This is a variety that if it continues to perform well should be considered in the future. Each year is different. For this reason, always look at yield data from at least three consecutive years before selecting a variety for planting. It is also a good idea to plant more than one variety since varieties perform differently under various environmental conditions. Some varieties also tend to perform better in different parts of the Panhandle. Past results form variety trials performed around the Panhandle can be viewed at the following web sites: 97-98 Results: http://soil-testing.tamu.edu/publications/832728-scs-98-25. PDF Based on long-term varietal testing Brent Bean notes the following wheat variety recommendations.
When considering a variety, characteristics such as plant height, disease and insect tolerance, coleoptile length (determines how deep the variety can be planted), and fall grazing potential should be considered along with yield data. Under dryland conditions it is hard to go wrong with Custer, Jagger, TAM 105, TAM 110 or Thunderbolt. All five varieties have good yield histories. Custer and Jagger are considered good grazing wheats, and TAM 110 has greenbug tolerance. Thunderbolt has good straw strength along with good tolerance to wheat streak mosaic and leaf rust. Under full irrigation, Hickok has been a consistent performer. Jagger, Ogallala, TAM 200, and TAM 110 should perform well under a wide range of conditions. Other irrigated varieties to consider are TAM 302 and 2137. Varieties to watch are Dumas (AgriPro) and TAM 400. If growers anticipate particular problems with diseases or pests, growers may consider planting the following varieties:
1) With soil test -- 1.5 lbs. N/bushel of yield goal less adjustment for soil N 2) Without soil test -- 1.2 lbs. N/bushel of yield goal Growers should limit fall N rates if not seeking grazing, and focus most of the N application in late winter and early spring, especially if you can put N through the pivot. Here's a scenario that might be appropriate for many South Plains growers applying ~100 lbs. actual N per acre for irrigated wheat: 1) Soil test for residual N; if adequate, credit to fall application, 2) Plant mid- to late-October applying ~30 lbs. N/acre for winter growth, 3) 20 lbs. N late January to mid February, 4) 50 lbs. of N at or pre-joint. The preceding program should be adequate for 70 bu/Ac wheat, but hit the topdress N application harder for a higher yield goal. In other words, 60-70% of the N is applied in late winter and early spring. If the crop goes through the winter in Feekes stage 3.0 (tillering) to 4.0 (beginning of erect growth), it does not require much N until spring growth. For mild winters, schedule more N earlier. Note that the greatest crop N use begins at jointing. When the spike is differentiating, you must have adequate N not to limit growth. Rapid N uptake occurs from late Feekes stage 5 (leaf sheaths strongly erect) to about Feekes 8.0 (flag leaf visible), when N uptake slows significantly. At Feekes stage 5, N affects number of seed per head and seed size, but won’t affect tiller numbers or number of heads harvested. Feekes stage 5.0 is an ideal stage of growth for topdress N. Later applications will not affect the potential number of seed per head. Once the first node is visible -- first hollow stem and jointing (Feekes stage 6.0) -- all grazing should cease if grain harvest is desired. Good response to topdress N is still possible at Feekes stage 6.0, but yield response is better at Feekes stage 5.0. Occasionally, if a wheat stand is thin, but uniform, an early N application may enhance tillering and thus increase the heads per square foot. All mid-season N applications should be either topdressed onto dry soil especially for high pH soils to minimize N losses, or if available, added through the pivot. For further information on wheat stages of growth and development obtain a copy of : "Growth Stages of Wheat: Identification and Understanding Improve Crop Management" by Dr. Travis Miller. It is available from County Extension Offices or http://lubbock.tamu.edu then click on 'other field crops' then 'wheat.' Planting dates for grain wheat. In general, for the Texas South Plains, there is little or no yield benefit in planting wheat for grain before October 1 (more susceptible to insects, excess water use, etc.). This is especially true south of Lubbock. Also, yield potential into early November is not significantly diminished, especially south of Lubbock, but keep in mind that the onset of colder soil temperatures, especially if below 45o F, will retard wheat stands if planted later.One risk, which occurs in many years, is that some wheat, often early or medium-early maturity varieties, can break dormancy early due to warmer weather. This makes them susceptible to damage from cold temperatures. Furthermore, a late freeze can hurt even longer maturity wheat varieties if the freeze occurs late enough. The further south, however, the less the risk. This represents a trade-off as earlier maturity wheat varieties often tend to yield a little more and can flower and complete much of their grain fill before the onset of consistent hot weather. Early/medium-early maturity wheat varieties such as Jagger, Custer, TAM 201, TAM 202 are good wheat varieties that have a high probability of maturing before hot weather occurs, especially south of Lubbock. CT
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