Alabama Cotton Insect Situation August 13, 2021

As the calendar turns to August the Alabama Cotton Insect Situation has really started to heat up. Plant bugs are still heavy in spots statewide, but stink bugs are becoming more and more of an issue as the crop continues to bloom. Some heavy bollworm egg lays have also been reported in parts of the Tennessee Valley. The overarching theme with many of these pests appears to be the drawn-out planting of corn due to wet weather this spring. Insect pests continue to trickle out of corn as the migrate into cotton fields. Spider mites are also in fields and have reached treatment levels over the past few days as well.

Plant Bugs

Plant bugs (tarnished and clouded) are still requiring treatments in some fields in Central and South Alabama. Cotton in the Tennessee Valley is under pretty substantial plant bug pressure. As we are now blooming, the black drop cloth is the preferred method to scout for plant bugs. Threshold is 3 tarnished plant bugs per 5 row feet. If clouded plant bugs are found, they should be counted as 1.5 tarnished plant bugs. Keep in mind that clouded plant bugs tend to do a little more damage to small bolls than tarnished plant bugs, thus the change in threshold.

Immature Clouded Plant Bug

Immature Tarnished Plant Bug

Stink Bugs

Adult Green Stink Bug

Thus far, stink bug pressure seems to be higher than normal. This is especially true in the Tennessee Valley. In fields where no controls with activity on stink bugs have been sprayed, stink bug pressure (and damage) has been quite high. Stink bugs are a consistent threat to cotton in central and south Alabama, so more controls with activity are used to stink bugs are used when spraying plant bugs. The most reliable method to scout for stink bugs is to sample bolls about 1 inch in diameter for internal sings of injury (pin-prick marks, warts or stained lint). Threshold is 10% internal injury from weeks 3-6 of bloom. Regardless of location in the state, if a “hard” chemistry has not been used by the 3^rd week of bloom, I would highly recommend finding a reason to use one.

Bollworms

We received reports of heavy egg lays in the TN Valley this week. No reports of escaped worms have been made (yet), but with 20%+ egg infested plants, there is a possibility. Outside of 2017, escaped worms have not been a big issue in Alabama but there can always be some fields that don’t go as planned. Aside from the terminals, bollworm moths seem to prefer to lay eggs on bloom tags (drying bloom petals). Thus, egg scouting efforts should be focused on in the terminals and the blooming zone (particularly on bloom tags). Currently, our recommended thresholds are based on the number of escaped worms found per 100 plants. Escaped worms may be found on bolls (often underneath the bloom tag), squares or white blooms. In Bollgard II and TwinLink technologies, escaped worms tend to be found in the blooming zone. Threshold is 5 worms (0.25 inches or bigger) per 100 plants. To date, we have seen no issues with 3 gene technologies (Bollgard 3, Widstrike 3, TwinLink Plus). We do not recommend treatment on these varieties.

Bollworm eggs on terminal.

Escaped worm feeding under
bloom tag.

Spider Mites

We have received reports of spider mites from the Wiregrass over the past week. Mites are in nearly every field statewide  at some level all year long waiting for a hot, dry stretch to “blow up.” As we write this, we don’t know what the incoming tropical storm system is going to do, but it looks likely rain events are coming. We do not know what that will do to spider mites approaching treatment levels currently, so making applications in front of the storm may be advisable. Treatment decisions require a bit of professional judgment. Threshold is when mites and their injury is widely distributed across the field. Coverage is critical for control of spider mites. Using the higher end of labeled rates is advisable as cotton is into bloom.

Parting Shots

We still have another 4-6 weeks left to make cotton in Alabama. Hopefully Tropical Storm Fred will bring some needed rain (but not too much). Keep scouting and spraying fields as needed. Up-to-date thresholds and insecticide recommendations visit the Alabama Cotton IPM Guide (IPM-0415). We will continue to put out information through twitter, this newsletter and the Alabama Crops Report Newsletter, Podcast and on the Pest Patrol Hotline. As always, if we can ever be of any help please don’t hesitate to let reach out.