Thursday, March 4, 2021

Thrips Management in Cotton for 2021

As the 2021 cotton production season approaches, it is time to start preparing for thrips management.

Thrips are the dominate insect pest of seedling cotton in Alabama. Each year, thrips infest 100% of the acres planted statewide. Due to this, thrips must be managed with an at-plant insecticide. We have several options for at-plant management including insecticide seed treatments (ISTs), and in-furrow liquid or granular materials. There are pro’s and cons of each approach, so deciding which strategy to use may make sense for one situation and not for another.

Insecticide Seed Treatments 

In recent years, the neonicotinoid insecticide seed treatments have begun to show reduced efficacy, particularly thiamethoxam. For this reason, we no longer recommend the use of thiamethoxam alone (e.g. Cruiser, Avicta) to manage thrips in cotton. If an IST is used, we recommend it be imidacloprid based. Examples of imidacloprid based ISTs include Gaucho and Aeris (imid. + thiodicarb). Although not bullet proof in all cases, these products typically provide adequate protection from thrips under light to moderate pressure. Another option would be to treat seed with acephate (e.g. Orthene) or to supplement an imidacloprid IST with an additional treatment of acephate. The only problem with this approach is that one a bag of cotton seed is opened and over-treated, it cannot be returned if not planted in most cases.


In-Furrow Insecticides

Another option is to use in-furrow insecticides to supplement or replace ISTs. In-furrow liquid applications of imidacloprid generally provide very good control of thrips. Acephate may also be used and provides good control under the right conditions. Acephate should not be used in place of an IST as it does not provide long residual control and may be leached out of the rootzone prior to plant uptake under cool, wet conditions. Another option is AgLogic (aldicarb). This granular product provides excellent control of thrips and can also be used to manage nematodes as well.

Foliar Insecticides

Foliar insecticide applications should be made to supplement at-plant thrips management, not be used as the “first line of defense.” Cotton is susceptible to thrips injury until around the 5th true leaf stage. Generally foliar applications are most effective when made at the 1-2 true leaf stage. The Thrips Infestation Predictor for Cotton can be used to show the relative risk of thrips injury for cotton planted at a given location and date. This can be used to help plan out fields or planting dates for cotton that will likely need a foliar application. Several options are available to use to supplement at-plant insecticides.

·         Acephate (4-6 oz/A) is an effective and relatively inexpensive option, however it has the potential to flare secondary pests such as spider mites and is the least rainfast of the available recommended options.

·         Bidrin (3.2 oz/A) is another option that is effective and less likely to flare spider mites and is more rainfast than acephate, however it is more likely to cause crop injury when tank-mixed with herbicides.

·         Dimethoate (6.4 oz/A) is another cost effective and efficacious product with good rainfastness, however it is the most likely to cause crop injury when tank-mixed with herbicides.

·         Intrepid Edge (3 oz/A) is another effective option. Intrepid Edge is less likely to flare secondary pests but may need the addition of a surfactant to help with efficacy.

·         Pyrethroids are not effective and should not be used to manage thrips.

In order to get the 2021 cotton crop off to the best start possible, at-plant thrips management is a must. Supplemental foliar sprays may be necessary in certain situations, particularly with earlier planted cotton when nighttime temperatures are cool. More information about thrips can be found in Pests of Alabama Cotton: Thrips (ANR-2718). For more information on thresholds and insecticide recommendations, visit the Alabama Cotton IPM Guide (IPM-0415). Results from 2020 cotton insect research trials can be found in 2020 IPM Projects Advancing Alabama Cotton Production (ANR-2735).

Thursday, February 4, 2021

Looking Back as a Career Winds Down: 50 Years of Cotton IPM in Alabama (1971-2021)

 

I began my career as an Extension entomologist at Auburn University on April 24, 1972. To put that into perspective – Richard Nixon was president and the Vietnam War was still ongoing. I have worked under the direction of eight Alabama Cooperative Extension Directors and numerous Deans of the Ag School/Experiment Station.

It has been quite a journey to have been a part of the most evolutionary period ever in cotton insects. I began my career when boll weevils were the key and dominant cotton insect in Alabama and as part of the new USDA-Extension cotton IPM educational initiative. Each cotton producing state received new federal funding to add one additional cotton entomologist. Two states, North Carolina and Arizona, added an additional entomologist a year earlier, in 1971. In 1976, this increased educational program had proven so successful that additional funding was provided that enabled the Alabama Cooperative Extension Service to add two additional area entomologists (Decatur and Selma) and four multi-county IPM agents (three in the Tennessee Valley, where a high percentage of the cotton acreage was at that time, and one in central Alabama). The special funding for this program effort continued for more than 30 years. The goal of this new program was to increase the awareness of a management approach to controlling cotton pests. 

The Extension cotton scouting program and use of economic thresholds, which forms the basis of a management approach, was initiated by Drs. Walter Grimes and Roy Ledbetter with the aid of Mr. Frank McQueen (survey entomologist) in the late 1950’s and early 1960’s. During the early to mid 1970’s our primary cotton insecticide tool was the organophosphate class of chemistry. The organophosphates, such as methyl parathion and Guthion, were characterized by fast acting activity but short residual. In addition, most chemicals in this class had acute human and mammalian toxicity. The phosphate chemistry had excellent activity on the boll weevil but brought on resistance in the tobacco budworm and secondary pests such as spider mites and whiteflies. The heavy use of phosphate insecticides also caused major problems with delayed maturity of the crop. This problem with delayed maturity was so pronounced that a special session was added to the Beltwide Cotton Research and Control Conference in January of 1976. Another type of insect control tool, that many of today’s growers do not remember, was available during the 1972-1989 window. This tool was the ovicide (worm egg only) chemical chlordimeform, sold as Galecron and Fundal. This chemical impacted cotton IPM scouting programs by creating a need to change to twice per week field monitoring (scouting). The life stage of a bollworm or tobacco budworm egg was only three days, so the increased egg counts had to be detected and targeted with an ovicide within a three day window when egg numbers peaked.

In 1976, the pyrethroid class of chemistry became available, first under an EPA issued emergency use permit (EUP). In 1978, pyrethroid insecticides received full but conditional registration and became the major player in cotton insect control for the next decade. For a few years, pyrethroids were highly effective on most all cotton insects. Insect losses were very low, yields reached a new higher plateau, and maturity issues disappeared. Due to extended residual from the pyrethroid insecticides (Ambush, Pounce, and Pydrin) application intervals for the boll weevil could be extended from 5 to 7 days. However, during the decade of the 1980’s, depending on the area of the Cotton Belt, tobacco budworms became resistant to the pyrethroid class of chemistry.

It was during this time period that the final plan to eradicate the boll weevil was being developed. This program had been under development for more than a decade. One of the big driving forces to eradicate the weevil was the possibility that boll weevils might develop resistance to the organophosphate class of chemistry. This possibility would have wrecked the cotton industry in the U.S. Pyrethroids had activity on the weevil but were not as effective as the phosphates and were initially significantly more expensive. The boll weevil never developed resistance to the phosphates, in fact, the phosphate insecticide malathion was the primary insecticide used for eradication.

In the Fall of 1986, the organized boll weevil eradication initiative reached Alabama. This program was first started in northeastern N.C. (Chowan Co.) a few years earlier. Twenty-one counties in southern Alabama were included in the first eradication zone. During the following 7 years the program was expanded throughout the remainder of the state (central AL – 1992, NE AL – 1993, and TN Valley – 1994). By the summer of 1995 no economic losses to the boll weevil could be found anywhere in the state.

During the active eradication program period (1986-1995), insecticide resistant tobacco budworms and impossible to control beet armyworms caused yield losses beyond anything ever observed or previously recorded. During one season, yield losses to beet armyworms alone were estimated to be about $40 million across the state. Pirate, a new highly effective chemistry that was under development by American Cyanamid, was requested for emergency use from the EPA multiple years. However, this request was denied until August of 1995, which proved to be too late to help with the beet armyworm outbreak that had been ongoing since 1987. At the end of the 1995 season the outlook for the future of cotton production in Alabama was bleak.

Fortunately, genetically altered Bt (Bollgard) cotton varieties, which had been under development and evaluated in select fields for the previous four seasons, became available to growers. This new technology was readily adopted by Alabama growers and 77% of the 1996 acreage was planted to Monsanto Bollgard varieties. This rapid adoption was primarily in self-defense following the heavy losses to worms the previous years. However, planting this new technology brought with it rules and regulations never experienced before by growers. Word was spoken that growers would never have to treat for worms again. This proved to be incorrect when in late July 1996 news of bollworm escapes in the Brazos River area of central Texas spread across the Cotton Belt. It was only about one week later when this escape bollworm and fall armyworm problem was observed in Baldwin Co., Alabama. Some growers wanted to give up on this new technology immediately. However, over the following years entomologists and growers learned more about what to expect form Bollgard cotton varieties and how to manage these escape bollworms, which could be controlled with a minimum of well-timed pyrethroid sprays. The following 10 years proved to be good for growers with overall improved yields and minimal insect losses and control costs.

It was during this low spray environment that the bug complex became more damaging to yields. In north Alabama it was the tarnished plant bug that had to be monitored and managed more closely. In central and south Alabama, as well as the remainder of the Coastal Plains of the southeastern U.S., it was the stink bug that became the dominant economic insect of cotton. Entomologists in the Carolinas, where the weevil was first eradicated, had reported that stink bug damage increased. However, populations of the southern green stink bug in the southeastern U.S. caused even greater damage than did the green stink bug species in the Carolinas. It took several years for growers and fieldmen to realize how devastating the stink bug could really be.

By the time better stink bug management was adopted, the Bollgard technology, with one Bt gene, began to lose its effectiveness and escape bollworms were more widespread . Experts had warned that this phenomenon would happen since the single Bt gene was never 100% effective on the bollworm species, as it was on the tobacco budworm. Anticipating this, Monsanto had begun work on stacking a second gene. This second Bt gene entered the market in 2009 and reduced this escape bollworm problem by about 90%, followed by Bollgard III in 2018. WideStrike genes from DOW AgroSciences (Phytogen varieties) first became available in 2005 and were followed by the third gene (WideStrike3) in 2014.

Cotton insect control overall from 1996 to 2020 has been good with no boll weevils or tobacco budworms and minimal escape bollworms in the system. However, sucking pests such as thrips, aphids, whiteflies (silverleaf) and spider mites have required monitoring and management. In addition, due to reduced tillage trends, certain sporadic or new pests have had to be contended with. Some of these are grasshoppers, cutworms, snails, slugs, and early season spider mites. However overall, the past two decades have required careful monitoring and selective management and control skills, but insect losses and control costs have been historically low and have served to keep the cotton industry profitable in Alabama.

The evolution of cotton insect management is so great that fire ants are now considered as the number one beneficial insect against escape bollworms in our reduced tillage system. It is felt by several entomologists that fire ants are playing a big role in allowing Alabama growers to continue to plant two-gene varieties, primarily DP 1646, without the need for costly diamide chemistry (Prevathon and Beseige) oversprays. The diamide chemistry, developed by Dupont, is highly effective when applied timely on most worm species. What would have been a significant development, had it not been for the introduction of genetically modified genes back in 1996, was the introduction (1996-98) of spinosad (Tracer) chemistry by DOW AgroSciences. For the first time since the development of synthetic pesticides in the 1940’s, caterpillar pests could be controlled with this selective chemistry while lady beetles and other beneficial insects were not affected and remained in fields.

More recent years of cotton insect control have been dominated or characterized by the emergence of sucking pests, such as aphids, spider mites, thrips, and whiteflies (silverleaf), and the bug complex (plant bugs, stink bugs, and leaf-footed bugs). As we moved into this reduced foliar spray era following the elimination of the boll weevil and tobacco budworm, our chemical tools became more selective. Our new caterpillar insecticides do not control sucking pests or the bug complex and the sucking pest insecticides do not control the bug complex or escape bollworms. Insecticides targeted for the bug complex give limited control of sucking pests or escape caterpillars. Tank mixes of two or more insecticides are again often necessary. In the 1950’s and 60’s most insecticides were formulated as mixtures at the distribution level. Now, these mixtures are prepared on the farm as the sprayer is being loaded.

The future will likely continue to be dominated by our current conditions. New advances may be limited. Few new chemistries will be developed. Development cost of chemistry cannot be recouped from cotton usage alone, as was done in the earlier years. New chemistry developed today must find market share with all row crops along with vegetables, fruits, nuts, and other grain and food crops. New advances will likely come in the form of genetics. These advances take years of research and development and as many or more regulations as do chemicals. A thrips-lygus gene is nearing the marketplace in 2021. Based on research, this gene may prove most effective on thrips with moderate activity on plant bugs. It will not help on stink bugs, which are likely to continue to be the dominant economic insect in Alabama and the Coastal Plains of the southeastern U.S. Rather than advancing the discipline of row crop and cotton entomology, our future may be described as a “stay ahead of resistance” in the decades ahead. Resistance issues are present today in the following species: thrips, plant bugs, bollworms, spider mites, aphids, and possibly other species. The greatest challenge in entomology today is staying ahead of resistance and managing sporadic pests such as slugs, snails, cutworms, grasshoppers, three-cornered alfalfa hoppers, leaf-footed bugs, and others. Reduced tillage has been a great advancement; however, this practice has created numerous cracks that are being filled by sporadic pests that require the attention of entomologist and fieldmen advisors.

In summary, the past 48 years of cotton production and insect management have evolved in many, and in some instances unexpected, ways. Examples include:

·       The change from intense cultivation to reduced tillage and heavy dependence on herbicides.

·       The development of major resistance issues with weeds and numerous insect species.

·       The development of increased problems with nematodes and, potentially in the future, plant viruses.

·       A shift from boll weevils to the stink bug complex as the most economic insect.

·       The change from phosphate chemistry to the pyrethroids and now the diamide chemistry.

·       The change from 5 day insecticide application schedules for boll weevils to 2 to 4 seasonal foliar sprays.

·       The escalation from nominal seed cost to very expensive seed and trait costs.

·       For most of the past 50 years, growers were using granular insecticides (Disyston, Temik or Thimet) at planting for early season insect control. In more recent years seed treatments, with neonicotinoid class chemistry, followed by foliar sprays were the standard practice for early season pests.

·       The change from moderate expenses per acre spread across the season to high, front-end budget inputs.

·       A shift from a few secondary pests to numerous new sporadic pests.

·       The change from Extension ag agents in every county to a regional agent with responsibilities spread over as many as 15 counties.

·       Early in my career, most Extension specialists had 100% Extension appointments and were not in academic departments at Auburn University. Most all of their research during those years was in the form of on-farm demonstrations. Now most all Extension specialists have split appointments (ex. 75% Extension, 25% research) and have professorial rank in our academic departments. These Extension specialists are conducting a high percentage of applied research on University research farms.

·       The shift from primary information sources of Extension agents/specialists and insecticide distributor salesmen to private consultants and well-trained commercial agrifieldmen.

·       The change from print media to electronic tools.

Entomologists who have been a part of the Alabama cotton pest management team over the past 48 years are: Roy Ledbetter, Frank McQueen, Ron Smith, Richard Davis, Glenn Worley, Barry Freeman, Tim Reed and Aaron Cato (post-doc). On April 1, 2020 Dr. Scott Graham assumed lead responsibility for this program. Dr. Graham is a native of Mississippi and has degrees working under prominent cotton entomologists (M.S. Mississippi State, Ph.D. University of Tennessee). Therefore, the program has great leadership for the future.

What an evolution and what a ride for an Extension entomologist over the past five decades. Always a challenge, always an additional idea on how to educate or have a more positive impact on cotton pest management. Job never complete nor finished, but most rewarding job in the world. Spent a career in trying to help my friends manage their insects. Knees are worn out but the mind is still going. Desire to be involved for a few more years in some capacity. I will end with a thought and a quote from one of my all-time favorite books, “Cotton is the greatest crop heaven ever gave to a country,” Red Hills and Cotton – An Upcountry Memory by Ben Robertson, 1940.

 

Wednesday, August 5, 2020

Cotton Insect Control for Remainder of 2020 Season

In most seasons, we would be entering the home stretch for cotton insect control by early August. While this may be true for fields planted on time in 2020, it is not the case for a lot of late planted, late emerging, late maturing fields this season. I hope we can narrow our focus to just a few species of insects for the remainder of this season. The primary group would be the bug complex (plant bugs, stink bugs, and leaf footed bugs). However, there are several other insects that could arise if weather conditions or other circumstances permit. These are spider mites, late season aphids and especially silverleaf whiteflies.


The insects of focus for the remainder of the 2020 season may not be as concerning as how long our management and control programs should extend into September and even October on our later maturing cotton. Let’s look at some general guidelines. If past seasons give us any trends, our escape bollworm issues should end by Labor Day. However, we should continue our monitoring as long as our late maturing fields have squares in the top of plants that would serve as a food source for a one-day old bollworm. Once all the squares are gone, escape bollworms will have a difficult time becoming established. The bug complex should eventually be dominated by stink bugs here in Alabama. This may consist of several species; the brown, southern green, leaf footed bug, and the brown marmorated (BMSB), which can now be found in many cotton growing counties. How long should we continue stink bug controls on late maturing cotton? Our general rule with our traditional stink bug species is to continue controls until the top bolls we hope to harvest are about 25 days old. When the BMSB is in the mix, we may need to protect even longer since this species will attack bolls from thumb nail size, up until they begin cracking. With our late maturing fields this season, we will need stink bug controls through at least the month of October. An application for stink bugs usually gives us 10-14 days of boll protection. However, as some fields mature out, just like with corn, stink bugs will move to younger cotton, or swag areas of fields that are still producing bolls or to late maturing soybeans. In other words, as our crops mature in September and October we will get field to field and crop to crop movement of stink bugs. As far as insecticide choices—Bidrin, bifenthrin or any other pyrethroid at a high-labelled rate should give adequate control. The best way to scout for stink bugs will be to examine bolls for internal injury. Just observing or using a sweep net or drop cloth for stink bugs is not very effective and often leads to underestimating the number present. 



Monday, July 13, 2020

Thoughts and Tips for Bollworm Scouting on 2 Gene Cotton for 2020


·       If monitoring 2 gene cotton in 2020, take note of the corn planting window in your area. This plays a large role in the emergence and movement of corn earworm (bollworm) moths to cotton in July and August. The more corn planting is spread out, the wider the emergence window of bollworms.

·       Bollworm moth activity is not constant throughout the season. Instead, it occurs in cycles especially through July. By August, generations of bollworms and tobacco budworms overlap. Fieldmen should detect the start of these peaks by focusing on eggs and newly hatched larvae in terminals/white blooms.

·       Scouting intervals for bollworms may be reduced to 3-4 days during critical windows on 2 gene cotton in 2020. Fieldmen could spot check select sentinel fields of similar variety and planting date on alternate visits to detect increased activity.

·       When monitoring for bollworm larvae or eggs on 2 gene cotton in 2020, be more concerned about detecting population increases early, and reacting if necessary, than quantifying exact numbers—for example: 18 vs. 28 per whatever.

·       Fieldmen should consider damaged fruit on 2 gene cotton in 2020, but treatment decisions will be more timely if primary focus is on eggs and/or newly hatched larvae.

·       Based on my observations during the Bt cotton era of the past 20 plus years, escape bollworm larvae do not feed on or damage as many fruiting sites per worm as they did in the pre Bt era.

·       In order to stay on schedule in 2020, fieldmen should consider only staying in a field long enough to make confident treat or not treat decision.

·       Pest Patrol Updates on cotton/soybean insects in Alabama are available again in 2020. To sign up for the Syngenta Pest Patrol Updates for Alabama, register online at https://www.syngenta-us.com/pest-patrol or register via text message by texting pestpat11 to 97063.


Monday, July 6, 2020

Tarnished Plant Bug Alert for Cotton



Due to abundant rainfall over most of the state in recent weeks, the migration of adult plant bugs from wild host (daisy fleabane) has been slow and extended over several weeks. This makes it difficult to make treatment decisions since the adult numbers may be below threshold level (8 per 100 sweeps) for several consecutive weeks. It is for this reason that we also use a pinhead square retention count (need 80% retention) in making treatment decisions. It is possible that a sub-threshold number for consecutive weeks will do economic damage. Large farmers spread over a wide geographical area (multiple counties) do not have the ability to treat individual fields on a particular day. As the result, when PGR and boron applications are being made, a plant bug insecticide is included.

               Plant bugs tend to go to the earliest planted cotton first. As we move through July, all fields will eventually reach the blooming stage. When cotton reaches the blooming stage, we will begin to find immature plant bugs that have hatched from the eggs that were deposited by the adults that migrated from wild host. In blooming cotton, we can no longer use the pinhead square loss in making treatment decisions. Immature plant bugs move deeper into the canopy and feed on large squares, which results in damaged “dirty” blooms. The treatment threshold for these immature plant bugs is 3 per 5 row feet using a black drop or shake cloth. The product Diamond is a great plant bug suppression tool when immatures occur at threshold level in blooming cotton. Diamond at 6 to 9 oz. per acre will give 2-3 weeks control of immatures. Diamond can be mixed with an insecticide such as Bidrin, Centric, imidacloprid (Admire Pro or generic), pyrethroid or Transform. The number of adult plant bugs usually begins to decline (natural mortality) after first bloom as the immatures increase. In fields where plant bugs go uncontrolled for weeks, the immatures eventually reach the adult stage. If this situation is allowed to develop, a field may have plant bug populations that include all life stages from eggs in plant stems, immatures to adults. When this situation is allowed to develop into an imbedded population, multiple applications on a schedule are required to being plant bugs under control. It should be noted that clouded plant bugs have made up part of the plant bug population since mid-June. Damage, treatment thresholds and controls remain the same for both plant bug species.


Clouded Plant Bug Immature


Clouded Plant Bug adult


Wednesday, June 17, 2020

Spider Mites


Cotton Insect Report

Following Tropical Storm Cristobal, spider mites are still building in parts of central Alabama. Spider mite infestations are rarely evenly distributed throughout the field and are almost always in clumps either near field edges or randomly throughout the field. Our threshold in the Alabama Cotton IPM Guide says to treat fields when mites are widely distributed and mottling of leaves is common. Determining when to implement controls can be difficult when trying to decide how many ‘hotspots’ suggest mites are “widely distributed” and justify a spray. Spider mites prefer hot, dry conditions and typically can be “beaten back” by a rainfall event. Fields with spider mite hotspots should continue to be monitored after rain, because populations can build back after several days of hot, dry conditions. Spider mites also tend to build following broad-spectrum insecticide applications for other pests.

To scout for spider mites, look for leaf stippling or reddening on the top of leaves. If these symptoms are observed, look on the underside of leaves for spider mites, which will be a yellowish color with two black “spots” on each side of its back. Exposing the underside of leaves to the sun may agitate mites, making them easier to see. Also look for mites one or two nodes above the most symptomatic leaves as they may have moved up to fresh leaves. There are a few miticides labeled for use in cotton that can be found in the Cotton IPM Guide. Abamectin (e.g., Agri-Mek 0.15EC) at 8-12 ounces per acre is the most economical option but rotating chemistries is necessary if multiple applications are needed. Historically, lower rates of abamectin (8-10 oz) have provided adequate control in younger cotton, while higher rates (12 oz) are needed later in the season when plants are larger.

Peanut Insect Report
We were recently notified that Nichino America received a supplemental label for the miticide Portal to use in peanuts. The labeled rate is 1.0 – 2.0 pints per acre with a minimum of 14 days between applications. The supplemental label must be in the possession of the user at the time of application.


Scott Graham and Ron Smith

Thursday, April 2, 2020

Grasshopper: Sporadic Pest of Seedling Cotton

Grasshoppers have been a sporadic pest of seedling cotton for 10 or more years. Growers reported observing high numbers of adult grasshoppers during harvest season in fall 2017. Overwintering populations are influenced by environmental conditions. Rainfall is likely more important than temperatures. Dry winters are favorable for grasshopper population since they overwinter as eggs in the soil. Grasshopper problems are sporadic and almost always associated with reduced tillage fields.

The primary grasshopper that damages cotton is the differential species which also overwinters as eggs in the soil. Eggs hatch from late March throughout April, May and June as soil temperatures rise and spring rains occur. The first nymph to leave the egg pod makes a tunnel from the pod to the soil surface through which the succeeding nymphs emerge. Nymphs feed and grow for 35 to 50 days before becoming adults which can then fly. The nymphs or immatures can only jump. Their development proceeds most rapidly when the weather is warm but not too wet. Mature grasshoppers mate and continue feeding on plants. About 2 weeks later, females begin to deposit clusters of eggs in the soil. Soil particles are glued together around the eggs to form a protective pod. Each pod may have 25-150 eggs. Most grasshopper species only complete one generation per year.

In fields with historical grasshopper problems, growers may want to take a more preventative approach by adding a grasshopper insecticide to their burn down herbicide. Since not all grasshoppers emerge from the egg stage at the same time, a long residual IGR (insect growth regulator) insecticide could also be utilized. Dimlin has proven to be a good management tool for grasshoppers. It has extended residual that provides good control of immature grasshoppers but will not control adults.

There are no established thresholds for grasshoppers in cotton and will likely never be since their feeding habits are so unpredictable. Some fields and some years may have grasshopper damage while other fields and years have the same level of grasshoppers but no damage. Preventative insecticide applications for grasshoppers are a judgment call. When grasshoppers are observed, and cotton is in the susceptible stage, treatments can be based on the risk level that an individual grower is willing to take.


Grasshopper problems are greater in lighter soils or soils with higher sand content. Damage often occurs in the same fields or farms from year to year. Grasshopper damage as stated is unpredictable but can potentially threaten a stand. Grasshoppers may feed on foliage, but most economic damage occurs when grasshoppers feed on the main stem of emerging (in the crook or cracking stage) seedlings. In some cases, grasshoppers may completely sever the stem, but
more often they will chew partially through the stem weakening the plant which will fall over at the feeding site.


Most all cotton insecticides will control immature grasshoppers when applied at a low labelled rate. Later into the spring, adult grasshoppers are very difficult to control with any insecticide, even at a high labelled rate. Acephate (Orthene) at 0.6 lb. active per acre has proven to be the most effective grower treatment for adult grasshoppers.