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Welcome to the first issue of the newsletter, FOCUS on Entomology, for the 1999 growing season. While newsletter content will center as always on insects in the major crops of our area, other issues will be covered as needed, including diseases, weeds, irrigation and of course agronomics. We simply cannot manage pests in crops without taking a more holistic approach. This year will be a transition year for FOCUS as we build on the web version of the newsletter while maintaining the paper version for one last year. With the appointment of Dr. Pat Porter to the Extension grain entomologist position in Lubbock last year, we gained the expertise to capitalize on the many benefits of using an electronic newsletter. The electronic delivery of FOCUS allows us to add more information than is practical with the printed version and we can now have electronic links to other sources of information and the ability to provide color photos.
FOCUS will be posted on the Center web site on Friday afternoon, providing readers a one to three day lead over those receiving the paper version via snail mail. This will be a building process. As with anything new, there will be some growing pains associated with the change. Some of you may have trouble accessing or reading information available through the links provided. If so, please let us know and we will try to resolve these problems. Some readers of the printed version do not have direct access to the web site either because they don't own a computer or maybe don't use an internet service. Hopefully you will be able to access the electronic FOCUS by using someone else's computer, perhaps at an agricultural business? JFL
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The 1999 crop season is upon us. Planting intentions indicated an increase in cotton acreage in the High Plains, perhaps up to 3.7 million acres, 200-300 thousand acres above normal. Most of the increase in acres was due to diversion of fields previously planted to corn. As usual, each year has its own challenges. This year, from the start, growers are faced with a serious cost-price squeeze - lower cotton prices, higher production costs. The good news is that, we have outstanding soil moisture across the region. Some areas out there have less than desirable soil moisture, such as parts of Howard and Martin Counties.
We are now about 6 to 8 weeks into the crop season. In areas south of Lubbock many fields were planted at the end of April. Planting began in earnest across much of the High Plains in the first week or so of May. During that period of time, we experienced very cool nights (lower 40s at Dimmitt), however, days warmed up pretty well into the lower 80s. After the first week of May, low temperatures climbed into the lower 50s and the planters began rolling across the entire region. A truly outstanding planting window appeared, with soil temperatures and moisture situation combining to make for superb planting conditions. Based on County Agent estimates, we were 80-85% planted by May 28th, which means that most of the crop was planted during a 3-week window starting in early May. Cotton was generally emerging 4-6 days after planting in many areas.
During the week of May 24th we encountered hail storms across the region that affected over 400,000 acres of cotton. Large hail and wind-driven rain damaged many homes and cotton fields. Rainfall amounts ranged from 2 inches across the Plains to up to 8 inches or more in some areas in Hockley County. Most seriously affected counties included Hale, Swisher, Lamb, Floyd, Cochran, Hockley, Lubbock and Crosby. It is a major challenge to get a handle on how much was replanted, but we suspect that some 200,000 acres of either totaled-out or severely damaged fields were replanted. Many growers had to struggle to meet the May 31st planting deadline for the northern most counties. Other counties affected by hail were afforded a bit more time to assess stand damage and seedling health due to the June 5th final planting date. This week, some fields which were initially considered marginally damaged from hail still had not recovered and were destroyed and replanted. Many of those fields had adequate plant numbers, but stem bruising and damage resulted in very slow recovery and poor vigor. Seedling disease was beginning to infect some low vigor seedlings, thus compounding the problem. Another storm damaged fields in Castro and Swisher Counties last week, resulting in an additional 5-10 thousand acres destroyed. Since those counties were beyond the final planting date, fields could be released and planted to other crops such as soybeans or sorghum.
Dryland planting continued into last weekend, especially in eastern Gaines and western Dawson counties. Thunderstorms dropped 3 to 4 inches of rain in the area. Many fields which were planted in the furrow encountered considerable soil deposition on top of the planted row, which resulted in the seed ultimately being too deep for successful stand establishment. Many growers were weighing replanting options beyond the final planting date in Gaines County (June 5) and Dawson County (June 10) due to the boll weevil eradication program. Rainfall events ranging from a few tenths up to an inch have continued over the last few days. Sand fighters should keep rolling to tie the soil down between rainfall events in order to prevent further damage from blowing sand.
Heat unit accumulation has been tracking somewhat ahead of schedule at Lamesa (about 5% above), about normal at Lubbock (about 2% below), and below normal at Halfway (about 14% below). In areas where sand and hail have not been major problems, cotton continues to grow very well. Poorly growing fields north of Lubbock are probably due mostly to low heat unit accumulation coupled with environmental damage. Hopefully, with warm temperatures, slow-growing fields will begin to overcome environmental damage. For growers who are continuing to plant cotton, table 1, which is based on data reported by Bilbro and Ray (1969), may be of value.
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to May 15 planting |
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Additional information dealing with replant, stand loss, skip decisions, and variety selection are available from your county Extension office or at the Extension Soil and Crop Sciences Departmental Website at College Station: Making Replant Decisions, Effects of Stand Loss and Skips on Cotton Yields, Cotton Variety Considerations Under Replant Conditions.
Other information will be posted intermittently during the growing season to that web site which has several aliases including: http://aggiecotton.tamu.edu.
Due to the excellent weed control system and the Paymaster replant policy, many growers have opted to plant Roundup Ready varieties this year. In some areas that were able to get cotton established early without much environmental damage, Roundup Ultra applications are underway. Many cotton fields are now in the 3-4 leaf stage. The early season over-the-top window for Roundup Ultra application closes when the cotton reaches the 4-leaf stage (or when the 5th true leaf is no larger than a quarter). In many areas where cotton has not been damaged and has grown off well, the over-the-top application window is rapidly closing. Where leaves have been knocked off plants, mainstem nodes should be counted to determine the appearance of the fifth true leaf. (View picture of application window)
Keep an eye on the development of your crop. We have recently been accumulating some 15 (Halfway) to 22 (Lamesa) heat units per day. Mainstem nodes are formed every 3-5 days, if we assume 60 DD60s per node. For 5 nodes of development, about 300 DD60s (60 x 5) are required. Watch the window!
As with any pesticide product, consult the label for specific information. Listed below are some tips for obtaining good weed control with Roundup Ultra applied over-the-top prior to the 4-leaf stage on Roundup Ready cotton:
Once the 4-leaf stage has been reached, use post-directed equipment:
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Prior to the current bouts of heavy rain, wind and hail, the Texas High Plains cotton crop had been planted in one of the narrowest time windows in recent memory. Cotton to the north got an early start while farmers to the south planted a little later than they would have liked. We were looking at a fairly uniform crop across the area that would have helped us in managing pests later on, especially boll weevils. Unfortunately, the severe weather that has roamed the area damaged and delayed some fields and destroyed others, requiring replanting. These later planted fields will need to be watched for increased pest pressure in late season. The up side of this weather pattern is that the rains have blessed us with an excellent moisture situation, especially important for our dryland crop.
Thrips are the first pest to have come to the attention of producers this year. This tiny insect has moved out of maturing wheat and into young stands of cotton where it uses its rasping mouth parts to damage the undersides of cotyledons, very small leaf buds and squares. Damage to cotyledons results in a silvering appearance on the undersides of these leaves. Damage to leaf buds results in crinkling of margin tissue, and under heavy attack, leaves will be reduced in size, blackened and even killed. Damaged squares simply do not appear, being shed early in their development. It is the damage to leaves that catches the attention of most folks, but it is the feeding on very small developing squares that results in yield losses.
The most prevalent species is the western flower thrips, which is 1/15th inch in size, straw colored and with wings as an adult (picture). The immature stage is lighter colored, lemony yellow to white, without wings and very, very tiny. Development from an egg takes about two weeks, while the adult can live for as many as five weeks. It is believed that open, warm weather allows plants to outgrow thrips feeding damage. While this may be so, more than likely it is the cold, damp, windy weather that encourages thrips to move from more open, non-yield threatening feeding positions; into the shelter of the terminal area where their feeding activity destroys squares and reduces yield.
Migration of thrips out of wheat has been a slow, delayed process this year as wheat field maturity has been slowed. There generally have not been heavy adult thrips numbers but still enough to trigger a treatment decision where an at-planting insecticide was not used. Immatures in much larger numbers have appeared in untreated fields this week, resulting in average counts of 7 or more per plant in two leaf cotton. Remember, the action levels that we generally use in this area are 1 thrips per plant for every true leaf present. Treatments are generally not warranted after squares begin to appear, at the 5-7 true leaf stage. (See publication: Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas 1999-2000 (PDF format)
While the at-planting use of insecticides is by far the superior thrips treatment, some producers feel it is an unwarranted expense. And some situations are also not particularly suitable for preventative treatments. This would certainly apply to dryland acreage. The cadillac treatment is of course Temik, in the 2 to 3 pound per acre range. Higher rates are unnecessary and costly unless nematodes are a factor. There are other soil-applied insecticides that are cheaper and effective but don't net as well. Seed treatments such as Orthene are also effective but don't provide protection as long as the soil-applied systemics. Those of you that did nothing at planting for thrips management might want to carefully scout your cotton, dissecting out the terminal area in search of immatures (picture of terminal scouting for thrips).
Banded foliar sprays can be inexpensive compared to the broadcast applications. The only down side to banded sprays is that they are often not of a timely nature because of weather delays, wet fields and the slower rate at which fields can be treated with ground rigs versus airplanes. Remember, timing is everything! Don't sacrifice yield to save application costs. Several insecticides are used for thrips control including Orthene, Bidrin, Dimethoate, Guthion and methyl parathion. (See publication: Suggested Insecticides for Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas 1999 (PDF format). While it may be convenient to combine a thrips spray with your Roundup application, waiting to apply with the herbicide may be too much of a delay in controlling thrips.
Most preventative treatments play out in 3-4 weeks. Some may last longer in certain situations. It would be wise to check cotton that was treated at planting if only to make sure it continues to be protected up to the squaring period. If at-planting insecticides are still working, there should be very few immatures present. Recent heavy rains may have leached soil-applied insecticides out of the root zone, necessitating augmentative foliar sprays. These same heavy rains may have also removed the thrips that were present, leaving only the damage behind. Don't treat these fields until you confirm there are enough thrips present to justify the cost. If boll weevil trap catches are heavy around your field when a foliar thrips treatment is warranted, you might consider using one of the insecticides that will control both thrips and weevils. I know this will be before square protection is necessary but may be beneficial in eliminating some of the adult weevils present that will live long enough to see squaring cotton. According to Monsanto, there is no compatibility problem between Roundup and any of the insecticides. I still would do a jar test just to be safe.
This could be a tough year for boll weevils. I know we said that last year and weevils all but disappeared until late August or early September. But......unlike 1998, we are anything but hot and dry. Certainly there are no indications of drought so far. And it was the drought in 1998 that all but wiped out the weevil population, at least during the bulk of the growing season, following record emergence of overwintering weevils. This year is different so far. Boll weevils did recoup their numbers late last year, putting a record number of weevils into overwintering sites. The winter was again mild resulting in excellent survival where moisture was adequate in the leaf litter. During our overwintering site survey in April, we did ascertain that sites were drier than the previous year and the percentage of live weevils found was lower than in 1998. But between the very high numbers that entered overwintering sites and the excellent health of those collected and examined, we knew there was a potential for heavy emergence this spring and summer. So far our GRID trap catches (http://www.plainscotton.org/bw99.html) and catches in traps monitoring individual fields have borne that out. Numbers of boll weevils emerging thus far are higher than last year and continue to be high at the close of this week. We have not detected early emergence as we saw last year, leading me to believe that suicidal emergence will not be as great this year. Also, following a mild winter there is almost always an extended emergence. Couple all of this with the present moisture situation and you have a mix of conditions that favor the establishment and survival of high numbers of boll weevils in area cotton fields unless you do something to prevent it.
Trap catches have been alarmingly high so far in some areas. Especially in the area south of an east/west line cutting through Plainview. Numbers averaging above 20 per trap week for a given field have not been uncommon. Record numbers as high as 100, 200, even above 500 per trap have been reported. This is a serious situation since many of these same fields are approaching squaring. Remember that adult weevils live an average of 12-14 days without squaring cotton. If you don't have traps out on fields that had late weevils last year you are already late, in some cases too late! I like to have traps established around fields two weeks prior to the week of squaring. The first week is to allow traps to get "settled in". The second week is your backup week just in case weather is poor the third week. The third week is the week when squares will appear and is the decision making week, unless weather conditions adversely affect trap catches forcing you back to using the 2nd week of trap catches.
According to TAMU guidelines, if traps around a given field average 2 or more weevils per trap per week, at least one overwintered weevil spray is justified. (see publication: Boll Weevil Management in the Texas High Plains (Plains Cotton Growers Website). I know many consultants that treated if they caught even a single weevil in any of the traps around the larger field. Why? Because we probably don't put enough traps around fields to get an accurate picture of the overwintered weevil population entering the field. It is often better to err on the side of conservatism. This year may be different for some folks though. If you farm in an eradication zone, the Foundation will be spraying fields once cracked bolls appear in fields. Essentially, all late season weevil applications will be taken care of by the Foundation. Normally, increases to damaging levels of boll weevil numbers in fields and heavy migration does not occur until late August and early September. Since diapause sprays could begin sometime between August 10 to 20, most fields would not see late developing boll weevil infestations. I think producers, especially dryland producers, should consider foregoing the overwintered boll weevil sprays where numbers are near the trap index threshold. Since nothing is certain in this life, I won't unequivocally make this recommendation.
Normally, overwintered boll weevil applications are made to delay the appearance of economically damaging populations until late into the season. One to four applications may be needed. (Boll weevil picture) The number needed is determined by the amount of pressure exerted by the emerging weevil population, whether emergence is extended, and how deep your pockets are. Certainly, if you are catching 4 or more per trap per week, as squaring approaches, you should consider an automatic 2nd application 5 days later. But what if you are catching 50, 60 or even higher numbers as squares appear? While there is limited research data available, I would suggest that you are no longer looking at delaying economic damage from weevils, you are in a fight to prevent it right now. This high a trap number is indicative of a level that will cause excessive square loss, much like that associated with heavy fleahopper infestations.
Overwintered boll weevil treatments are some of your cheapest applications. These can be banded on with a ground rig, cutting cost by up to 2/3rds. Later broadcast treatments are much more expensive. The only downside to these applications may be timeliness. If applications are not applied before pencil eraser sized squares are present, then weevils will gain entry to the field and all may be lost. Just don't be late! Several materials are available including Guthion, endosulfan (Phaser and Thiodan), malathion, methyl parathion, Penncap M, and Vydate. Vydate is favored by many because it is both efficacious and less prone to cause secondary pest problems. JFL
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Corn rootworm larvae are hatching and feeding on unprotected corn roots. Corn fields that were planted to corn last year, and especially those that have been in continuous corn, are at greatest risk of significant rootworm pressure. This year's larvae are hatching from eggs laid in soil by adults in July, August, and September last year.
Corn rootworm larvae are from 1/16 to inch long with a dark head capsule and a dark brown spot on the posterior end (picture courtesy of Marlin Rice, Iowa State University). Rootworms have three larval instars (stages) and can cause severe damage. First instar larvae are very difficult to find, both because they are small and because they prefer to feed inside corn roots. Older larvae feed inside and outside roots. Even though rootworm damage is being done now and for the next few weeks, the effects of this damage might not appear until much later in the season.
Typical root feeding (pruning) appears as missing roots or as holes bored into roots (picture courtesy of Marlin Rice, Iowa State University). Light rootworm infestations can result in minor root damage, but do not do lasting harm because roots will later regrow (if water and nutrient levels are adequate). More severe infestations cause damage for which the plant cannot compensate. Inadequate root systems will predispose plants to water stress, above-ground goosenecking may appear, and yields may be reduced.
While many growers choose to apply rootworm insecticides at planting, others prefer to wait until cultivation. Most cultivation-time rootworm insecticides can be applied as a rescue treatment as well. Application in a rescue mode builds a barrier between roots and rootworms seeking roots from the surrounding soil. This will help prevent further root damage, but it will not necessarily eliminate significant root feeding.
A future issue of FOCUS will discuss monitoring adult rootworms in order to determine whether one should use a rootworm insecticide next year.
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Corn Pest References Corn Rootworm Insecticide Consistency - 7 Years of Tests (Iowa State Univ.) |
| Efficacy of Soil Insecticides on White Grubs and Mexican Corn Rootworm (Wharton County) 1 (Roy Parker) http://lubbock.tamu.edu/ipm/AgWeb/r_and_d/1998/Roy%20Parker/Soil%20Insecticides/SoilInsect.html |
| Evaluation of Granular Soil Insecticides For Corn Rootworm Control (Gonzales County) 4 (Roy Parker) http://lubbock.tamu.edu/ipm/AgWeb/r_and_d/1998/Roy%20Parker/Granular%20Soil%20Insecticides/GranularSoil.html |
| Managing Insect and Mite Pests of Texas Corn (1995) http://entowww.tamu.edu/extension/bulletins/b-1366.html |
| Pest Management Guide for Corn (Univ. of Nebraska, 1999) http://ianrwww.unl.edu/ianr/entomol/pmguides/pmguides.htm |
| Insect Management for Field Corn (Kansas State Univ., 1999, PDF) http://www.oznet.ksu.edu/library/ENTML2/MF810.PDF |
Heavy Banks grass mite infestations were reported by Cherinell Riley (EA-IPM Parmer and Bailey Counties) in one corn field near Farwell on Tuesday, June 8th. The distribution of mites was typical of early season mite infestations; along the edge of a road or in corn adjacent to wheat. This is not unusually early in the season, because mites overwinter in wheat, and as the crop matures, use the winds as a means to disperse to new green hosts. With our predominant winds out of the southwest, we often see these early infestations getting started on the southwest sides of fields.
Banks grass mites do not survive well or reproduce quickly on vegetative-stage corn. Light or moderate infestations are often reduced by beneficial insects (especially minute pirate bugs and western flower thrips) or rain. However, heavy infestations might justify chemical control. Because early season insecticide use can severely impact beneficial insects and thus hinder later biological control, think this one over carefully before deciding to treat. It is possible that early treatment could increase the need for treatment later in the season. Comite II will control Banks grass mite infestations and still preserve many of the beneficial insects in treated area. If the mites are localized along a road or near a wheat field, consider treating only the infested area; perhaps 40 to 60 rows nearest to the source of the mites. Best results will be achieved with ground equipment and a directed spray targeted at the undersides of leaves.
Newly hatched corn borers were reported by Johnna Patterson (EA-IPM Castro and Lamb Counties) on corn in Castro County. While these larvae were not abundant, they are the first report in the High Plains this year. Greg Cronholm (EA-IPM in Hale and Swisher Counties) is reporting above average SWCB captures in his traps. European corn borer and southwestern corn borer moths are flying now, and populations will continue to increase. At this time of year, moths of both species prefer to lay eggs on larger plants, and seedling corn is not preferred. We will have more information on corn borers in the next edition. RPP
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In light of recent hail damage on cotton, many producers quickly replanted their cotton. Because of the late date for replanting back to cotton, however, some producers may need options regarding alternative crops. Before replanting to sorghum, soybeans, sunflowers, or other crops, a careful evaluation of cotton plant density should be considered before destroying damaged cotton. Randy Boman, Extension cotton agronomist, suggests producers may be better off leaving their current crop at stands as low as 1.5 plants per row foot. As usual, goals of the producer and production economics will dictate which crop may be more suitable. Once the decision is made to replant to alternative crops, producers should check their compliance with government programs, which may dictate which alternative crops can be planted without losing base or benefits.
Foremost among replanting considerations are likely problems with residual cotton herbicides. Be sure to consult product labels for rotational crop restrictions for the herbicide you used on cotton. If faced with replanting an alternative crop, in some circumstances the planter may be adjusted to "break out" the treated soil in order to get below the herbicide zone. It is recommended that producers avoid "pulling" the treated soil toward developing plants during cultivation until later in the season in order to reduce potential for herbicide effects on developing plants.
For sorghum in the Southern High Plains, full season hybrids should not be planted after June 20 for the Lubbock area, medium maturity no later than June 25 to July 4, and early maturity hybrids may be planted up to about July 15. Although sorghum prices are poor, sorghum still might be a good choice for 1999 dryland as soil moisture in most areas is good, and early to mid-June is a good time to plant dryland sorghum. Check with your seed company for the recommended planting date for a particular hybrid. If planting late sorghum, midge infestations and other insects may be a problem so plan ahead for insecticide applications if needed. Herbicide carryover injury from cotton fields may be a particular concern from the likes of Treflan, Prowl, Caparol, Cotoran, and Karmex in soil residues. These herbicides may injure sorghum, particularly on sandy soils where residues could be relatively deep in the soil due to recent rains. The problem of herbicide residues in soil can often be avoided in heavier textured soils with a buster planter to establish a herbicide-free seed zone. Again, consult the chemical labels or your chemicals dealer. If Dual herbicide has been applied, safened seed can be planted directly into the treated soil with little risk of sorghum injury.
Soybeans may be an option on irrigated land although the recommended last planting date for dryland soybeans (June 10) is past. Soybeans can yield well even under limited irrigation. For the Southern High Plains, soybeans may be planted as late as July 10 and still make a crop, but late planting usually retards stalk growth and can make it hard to harvest the lower seed pods. Higher seeding rates and narrower rows may encourage higher pod set. Early to medium maturity group IV soybeans may be planted before June 15 to 25, but growers may switch to an early group IV or late maturity group III variety for later planting.
Oilseed sunflower contracts, including the newer mid-oleic oilseeds which offer a small price premium, are readily available in the Southern High Plains. Sunflower mid- to mid-late varieties (105-110 days) can still be planted to the north around Plainview until mid-June and up to the 25th at Lamesa. Shorter season sunflowers (85-90 days) can safely be planted up to July 10-15 around Plainview and July 15-20 in the Lamesa area. For information on contracting oilseed sunflowers contact Randy Redinger (Cargill), Plainview, 806-879-2372; or Northern Sun (a division of ADM), Goodland, KS, 800-542-7333. Northern Sun will work with growers on taking delivery at the turnrow if there is no facility accepting sunflowers in your area. I am not aware of any confectionary sunflower contracts still available. Oilseed sunflowers tend to have lower input costs than confectionary, and the later planting dates may substantially reduce the need to treat potential head moth infestations. CT
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Capture Approved for Corn. Capture 2EC has been approved for use on field corn, popcorn, and corn grown for seed. This pyrethroid insecticide controls many insects such as corn earworm, European corn borer, southwestern corn borer, and corn rootworm adults. It also controls mites, including twospotted spider mite at higher rates. Capture has a 30-day preharvest interval and a 12-hour restricted entry interval. Consult your chemical dealer or FMC for more product information.
SpinTor 2SC Approved for Sweet Corn. SpinTor 2 SC (Dow AgroSciences) has been approved for use in sweet corn for control of armyworms (including fall armyworm), corn earworm, southwestern corn borer , European corn borer larvae, and western bean cutworm. Applications may be made by broadcast, directed spray, or chemigation. Growers must have supplemental labeling in their possession before they can apply through chemigation.
SpinTor 2SC Approved for Potatoes and Sweet Potatoes. SpinTor 2SC (Dow AgroSciences) has been approved for foliar insect control on tuberous and corn vegetables, including (but not limited to) potatoes and sweet potatoes. SpinTor is labeled for control of Colorado potato beetle, European corn borer, dipteran leafminers, thrips, armyworms, and loopers. Chemigation may be used to apply SpinTor 2SC to potatoes, but growers must have supplemental labeling in their possession. RPP
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Texas Agricultural Extension Service Route 3, Box 213AA Lubbock, TX 79401-9746
Production: Michelle Coffman
Educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socioeconomic 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. |
