By Dominic Reisig
To answer this question, you need to know when the field first reached cutout, which is at 4 nodes above the first position white flower. Keep in mind that the last effective bloom date (the point at which there is a 50% chance the bloom will set a harvestable boll) for North Carolina is generally between August 20 – 25, but can range from August 15 – September 1st depending on fall weather and location within our state. So generally, any squares that have not bloomed by this point are likely not going to matter significantly for yield. Even if they do make it to harvest they will likely contribute little to overall yield if the bottom and middle crop is good. Please consider this before investing in the cost of an insecticide application that may not be 100% effective (see insecticide trial results below).
Plant bug management after cutout really needs to focus on keeping the internal boll injury to a minimum. Like stink bugs, plant bugs can feed on bolls and, like stink bugs, plant bugs transmit pathogens that can stain lint or cause boll rot and they can interfere with locule development. Occasionally bolls can abscise from plant bug feeding. While most stink bugs in cotton (brown and green) prefer to feed on medium (just under an inch in diameter) and small bolls (~1/2 inch diameter), plant bugs prefer to feed on small bolls. Internal boll injury from stink bugs and plant bugs is indistinguishable, so it is important to scout!
Be sure to rotate insecticides, especially if you’ve used multiple sprays. Results from some previous plant bug insecticide trials can be found here and results from this year’s trial are below.
Please note that the labeled rate for Bidrin and plant bugs is 4-8 oz and only 3.2 oz was used in this trial.
Please note that the labeled rate for Bidrin and plant bugs is 4-8 oz and only 3.2 oz was used for the first application. Second application is denoted by fb (fb= followed by) and was made seven days after the first application.
Source: uga.edu