Young larvae feed in groups on young leaves, scraping the surface and leaving small holes. Mature larvae feed on the whole leaves, starting from the edges and moving towards the veins, leaving only the midrib and veins (a process called skeletonization). Later on, they also feed on young shoots, buds and bolls. Black excrements on the leaf surface are a common sign of the presence of the pest. Outbreaks may happen sporadically, depending mainly on weather conditions, and can cause yield loss if severe. Semiloopers are only a significant threat to the crops if occurring in high numbers and attacking young plants. As they grow older, plants get more and more resistant to this pest.
Damage is caused by the larvae of Anomis flava, a moth that can be found in most parts of the world. Adult moths have orange brownish forewings traversed by two grey zigzagging lines near the edge. A conspicuous orange, triangular mark covers up to half of the top part of the wing, closest to the body. Hindwings are light brown, with no special features. Females lay approximately 500-600 round eggs on leaves. Young larvae are of a pale green color and with thin yellowish lines clearly separating the first five segments. Older larvae turn brownish or black and develop two dorsal yellowish lines. The pupae are of a brownish color and can be found on folded leaves. The English name semilooper refers to the way larvae move forward, forming an arch with their body.
Semilooper management is based on regular scouting for eggs or small larvae. Some species of the parasitoid wasps of the family Ichneumonidae, Braconidae, Scelionidae, Trichogrammatidae and Tachinidae can be used as biological control method. You can also use neem oil sprays to control population peaks. For example, neem seed kernel extracts (NSKE 5%) or Neem oil (1500ppm) @ 5ml/l can be sprayed.
Always consider an integrated approach of preventive measures together with biological treatment if available. Extensive insecticide use can lead to resistance in the pest. As larvae become increasingly resilient to insecticidal treatment while growing, scouting for eggs and young larvae is crucial. Treatment is recommended during the egg stage. Insecticides containing chlorantraniliprole, emamectin benzoate, flubendiamide, or esfenvalerate can be applied. Chemical treatment may be inviable in low-value crops.