Cotton, a staple fiber used globally, originates from the Gossypium plant, which is vulnerable to insect pests throughout its life cycle. The fiber is composed of nearly pure cellulose, a compound few organisms can digest, though some specialized insects target it. The living plant and its seeds are rich in proteins, oils, and starches, making them a nutritious food source for many arthropods. Pests attack the plant in the field, and different insects target the harvested fiber and finished goods in storage or the home.
Pests That Target Developing Cotton Plants
Field pests target either the plant’s reproductive structures or its sap. The most destructive insects consume the fruiting parts: the squares (flower buds), flowers, and bolls. The boll weevil, a snout beetle, attacks squares and small bolls by puncturing them to feed or lay eggs. This damage often causes the plant to shed the punctured squares, resulting in significant crop loss before the fiber can form.
Lepidopteran larvae, known as bollworms or budworms, also feed on these developing structures. These caterpillars burrow into the bolls, consuming the internal lint and seeds. Their feeding introduces moisture, facilitating fungal or bacterial infections that cause the bolls to rot internally.
Sap-sucking insects weaken the plant by piercing tissues and extracting fluids. Species like aphids, jassids, and whiteflies use specialized mouthparts to tap into the plant’s vascular system. Aphids excrete a sugary substance called honeydew, which coats the cotton fiber in open bolls. This contamination reduces the quality of the lint and makes it difficult to process during ginning.
Insects That Feed on Cotton Fabric and Stored Products
Once harvested and processed, cotton fiber and finished goods become targets for household pests. Silverfish are one of the few species capable of digesting the cellulose in cotton and linen fibers. They are drawn to textiles treated with starch sizing or stored with paper, as these provide a readily available carbohydrate source. Their damage appears as irregular scraping or holes in the fabric’s surface.
Common fabric pests, such as carpet beetles and clothes moths, primarily seek animal-based proteins like keratin found in wool or silk. Cotton is attacked when it is soiled with organic contaminants like food stains, perspiration, or body oils. These impurities provide the necessary nutrients for the larval stages to develop, since they cannot digest pure cellulose. Blended fabrics, such as cotton-wool mixtures, are also susceptible, as insects chew through the cotton to reach the desirable animal fibers.
Recognizing Signs of Infestation and Damage
Identifying an infestation requires observing distinct damage patterns in the environment. In the field, damage to reproductive structures is indicated by small, flared, or blackened blemishes on young bolls, often caused by feeding punctures. Immature bolls that turn yellow and drop off prematurely suggest an internal feeding problem. Leaf damage is also visible, ranging from skeletonization, where soft tissue is eaten away, to a scorched appearance at the leaf edges, sometimes called “hopperburn.”
Signs of infestation on fabric and stored goods are typically concentrated in dark, undisturbed areas. Small, irregularly shaped holes in clothing or linens are a common indicator of pest activity. The presence of tiny, pepper-like fecal pellets, known as frass, often accumulates in the folds of damaged material. Fabric-feeding moth larvae may also leave behind silken threads or small, tube-like casings constructed from the fabric fibers. Shedded, translucent skins left near the damaged item can also point to the presence of silverfish or beetle larvae.