Caterpillars, the larvae of several moth species, are significant pests of strawberry plants. These hungry larvae cause noticeable damage to foliage and fruit in home gardens and commercial operations. Understanding which specific pests are present and their unique feeding patterns is the first step in protecting your harvest.
Specific Larvae That Target Strawberry Plants
Strawberry leaf rollers, including species like Ancylis comptana, are common pests. These slender, pale green to brown caterpillars grow to about three-quarters of an inch long and wiggle when disturbed. Their defining characteristic is folding or rolling a strawberry leaf and securing it with silk webbing, creating a protected shelter where they feed on the tissue within.
Cutworms, the larvae of various Noctuidae moths, are a significant threat. These smooth-skinned caterpillars range from grayish to tan and tend to curl into a C-shape when handled. Cutworms are nocturnal feeders, hiding just beneath the soil surface or under plant debris near the base of the plant during the day.
Armyworms, such as the beet armyworm (Spodoptera exigua), are major strawberry pests known for their voracious appetites and tendency to feed in large groups. These larvae are usually green with distinct stripes and can be identified in some species by an inverted ‘Y’ shaped marking on their head. Unlike cutworms, armyworms are often found climbing and feeding on the upper parts of the plant, including the flowers and fruit.
Recognizing Feeding Damage on Fruit and Foliage
Leaf rollers are identified by foliage that appears tightly bound or folded, revealing skeletonized leaf tissue when unwrapped. This damage is concentrated within the silken shelter and can significantly reduce the plant’s photosynthetic capacity. Some leaf roller species also feed on the surface of the fruit where it touches a leaf or the calyx, sometimes tunneling shallowly into the berry.
Cutworm damage often appears as severed plant stems or irregular, large holes chewed into the foliage, especially on young plants. On ripening fruit, cutworms create pronounced holes, frequently near the base or sides of the berry resting on the ground. Young armyworm feeding can result in the skeletonizing of leaf undersides, leaving only the veins intact.
As armyworms mature, they chew large, deep holes into both green and ripe strawberries. This fruit damage is often concentrated around the calyx, or green cap. Any break in the fruit skin allows access for secondary infections, such as mold or rot, which can quickly ruin the entire berry. Observing the specific pattern of injury is a strong indicator of the pest responsible.
Safe Management Strategies
Controlling caterpillar populations begins with cultural practices that reduce the environment’s attractiveness to pests. Regularly removing plant debris and controlling weeds eliminates the hiding spots and alternative food sources favored by cutworms and armyworms. Handpicking is a highly effective manual control method, especially for cutworms found by gently scratching the soil near any recently damaged plant stem.
Physical barriers, such as lightweight row covers draped over the plants, prevent adult moths from laying eggs on the foliage, stopping the infestation before it begins. For a biological approach, the microbial insecticide Bacillus thuringiensis (Bt) is a targeted and safe option. The kurstaki strain of Bt is highly specific to the digestive systems of moth and butterfly larvae, meaning it does not harm beneficial insects or humans.
Bt must be ingested by the caterpillar to be effective, requiring thorough coverage of the foliage. It works best when applied to young, actively feeding larvae. Since sunlight quickly degrades the bacterium, applying Bt in the late afternoon or evening maximizes its effectiveness. Using these integrated strategies helps manage pest populations without resorting to broad-spectrum chemical treatments.