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. 

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.

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

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

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.

Early Season Thrips Control Important

Cotton planting and early season thrips management are almost upon us. We are fortunate today to have varieties that have three-plus bale yield potential. While we can’t control rainfall patterns for 2020, we can make sure that other factors such as early season insects, especially thrips, do not stunt or delay growth and development of seedling cotton.

Seed treatments alone are not as effective as in-furrow granular insecticides used in the past. Because the seed treatments imidacloprid (Gaucho) and thiamethoxam (Cruiser) have lost some or much of their effectiveness due to insect resistance, we are forced to add additional thrips-suppressing measures such as in-furrow or foliar sprays in our management programs. Research has shown that foliar thrips sprays are most effective when applied at the 1^st true leaf stage or very shortly thereafter. Such treatments on early planted cotton may be needed before growers finish planting later fields. Furthermore, an initial, timely spray may be most beneficial even before the 1^st true leaf has visible thrips injury.

We now have a tool that helps us know when this first foliar spray may be most effective. This tool is a Thrips Prediction Model. It is quite accurate in forecasting thrips pressure based on planting date and local weather. The model can be accessed at climate.ncsu.edu/cottonTIP. To indicate your farm location, scroll across the map to your site and click to drop a red pin. You then select anticipated planting date. The model accesses nearest weather station information for temperature and rainfall, data which enable predictions about the growth of seedling cotton as well as the status of wild hosts that serve as sources for thrips migration.

We have determined that thrips migration from adjoining hosts can peak early, mid, or late in the planting window. Since weather is a big factor in both seedling growth and the dry-down and maturity of wild hosts, the accuracy of the model improves when it is used as close as possible to the actual planting date. The model color codes the level of predicted thrips injury:  GREEN=low pressure, YELLOW=moderate pressure, or RED=high pressure. Based on 2019 experiences, a model prediction of RED indicates that an automatic foliar spray will be necessary, even before leaf symptoms are evident.

Insecticide choices for foliar thrips treatments are listed in the Extension Cotton IPM Guide – IPM-0415. They include acephate (Orthene or generics), dicrotophos (Bidrin), dimethoate (or generics), and spinetoram (Radiant or Intrepid Edge, which contains Radiant).

Since the model will likely contact the same weather station even if you plant in multiple counties, it makes sense to simply use one pin as your farm location. However, it is beneficial to run the model with varying planting dates, probably at least once every 7 days. Different regions of the state (North, Northeast, Central, Southeast, Southwest) may have significantly different thrips pressure as occurred in 2019.

To increase our chances of profit for 2020, we need to begin the season with the goal of producing the highest possible yield. Insect-wise, this begins with preventing the yield robbing and delaying effects of thrips injury.