Cotton Bollworms are an invasive pest that destroys the bolls, the rounded seed capsule, of cotton. The adult form of these pests, a large cream-colored moth, lay their eggs on the leaves and of the cotton plant. These eggs, which are also cream colored but turn a darker brown, are about the size of a pinhead, and hatch within two to three days.
The adult moth stage of the Cotton Bollworm is easy to spot and can be seen during the day around infested plants, but the eggs and larva can be harder to see due to their size. These larvae will be about a fourth of an inch long, with a body color that can range from pink to dark brown, but a series of stripes, running lengthwise down the body, will help distinguish a pest as the Cotton Bollworm.
These newly hatched bugs will start eating the smaller leaves and bolls at the top of the cotton plant, making their way down to more established seeds, damaging the larger bolls and destroying important parts of the plant. The caterpillars will chew holes into the bottom of the bolls and hallow them out. Even if a boll isn’t fully pierced by the bollworm, the damaged seed can still be destroyed, as shallow gouges can begin to rot.
How to Prevent and Manage a Cotton Bollworm Infestation
A Cotton Bollworm infestation can reduce the yield of a cotton harvest. Because of this, it is important to catch the infestation early. Timing is key to dealing with a Cotton Bollworm problem. Looking for the eggs and larvae of the Bollworm is something that anyone who grows cotton needs to do. There is not much that can be done once a majority of the bollworms have reached a larger size. Management of an infestation is targeted towards the eggs and smaller larvae.
But don’t be too hasty in trying to control a Cotton Bollworm infestation. Preventative treatment that would be given before the cotton plant blooms can damage the population of other bugs and insects that can help keep Cotton Bollworms and other pests at bay. The general rule of thumb is to treat an infestation only when ten eggs or 5 small worms per a hundred cotton plants are present in late July to early August. Use of insecticides is ineffective once the larvae of the Cotton Bollworm have grown to a larger size, usually about half an inch, but human meddling at this stage may not be necessary depending on the time of the season and growing conditions of the cotton.
An infestation of this insect is not usually a problem until later in the season when insecticides have interfered with the population of the bollworm’s natural enemies. Usually, at this point, the cotton plants are mature enough to still give a significant harvest, and any bolls that have not bloomed, or cracked, will not do so by the end of the growing season. So, damage done to these immature bolls by the Cotton Bollworm with not have any significant impact on the amount of cotton that can be harvested at that time.
Insecticides should only be used in dealing with a Cotton Bollworm infestation when the previously stated infestation threshold is met and when there is still a significant number of green, or underdeveloped, bolls on the cotton plants. Using an insecticide too soon will interfere with and kill off the natural predators of the Cotton Bollworm that help keep the population under control. This would cause the infestation to become worse.
The Cotton Bollworm is not usually enough of a concern that the farmer or grower needs to concern themselves with it. Natural predators of this pest usually keep the population of Cotton Bollworms under control, and it is only when insecticides kill off these predators that an infestation might become problematic. If it is late enough in the season that a majority of the cotton plants have bloomed, the grower may never need to concern themselves with it. The Cotton Bollworm may not have enough time left in the season to do any significant damage to the cotton crop.
Dealing with Cotton Bollworms is a balancing act. Interfering too soon can do more harm than good, but if a Cotton Bollworm infestation is not found soon enough on undeveloped cotton plants, then they can damage the bolls that have not bloomed enough to decrease the crop yield. If a Cotton Bollworm infestation does need human interference, the treatment does not require anything more than a common insecticide.
Learn more about Cotton Bollworms