English names: Cotton Leafworm, Tobacco Cutworm
Nordic names: Asiatisk bomuldsugle (DK), Aasianpuuvillayökkönen (FI), Bomullsfly (SE)
Major host plants
The host range of S. litura covers at least 120 species. Species attacked by S. litura in the tropics are both field and vegetable crops, and ornamentals.
On most crops, damage arises from extensive feeding by larvae, leading to complete stripping of the plants. Affected Plant Stages: Flowering stage, fruiting stage and vegetative growing stage. Affected Plant Parts: Leaves.
A map can be downloaded from EPPO's website. See instructions here.
Between 2 and 5 days after emergence, females lay 1000-2000 eggs in egg masses of 100-300 underneath leaves and covered with brown scales from the body of the mother. Fecundity is reduced by low humidity. The eggs hatch in about 4 days in warm conditions, or up to 11- 12 days in winter. Larvae develop through six instars in 15-23 days at 25-26 °C. At lower temperatures, for example on glasshouse chrysanthemums in Europe, larvae often go through an extra instar, and maturation may take up to 3 months. Pupation takes place in earthen cells in the soil and lasts about 11-13 days at 25 °C. Longevity of adults is about 4-10 days, being reduced by high temperature and low humidity. The life cycle can be completed in about 5 weeks.
The moths have a flight range of 1.5 km during a period of 4 h overnight, facilitating dispersion and oviposition on different hosts. They can accordingly fly quite long distances. In international trade, eggs or larvae may be present on planting material, cut flowers or vegetables.
Detection and inspection
Larval sampling can occur anytime foliage is present. Skeletonized leaves provide evidence of the presence of larvae. Early instars (<3rd) are likely to be found on the underside of leaves. The older larvae are night-feeders and are usually found in the soil around the base of plants during the day. They chew large areas of the leaf, and can, at high population densities, strip a crop of its leaves. In such cases, larvae migrate in large groups from one field to another in search of food. Though the markings are variable, a bright-yellow stripe along the length of the dorsal surface is characteristic of S. litura larvae. Adults can be caught in light or pheromone traps.
Pest status and importance
S. litura is an extremely serous pest, the larvae of which can defoliate many economically important crops. As for S. littoralis, the risk for S. litura is its possible introduction into glasshouses in most parts of Europe, where it may damage many ornamental and vegetable crops. Although control with insecticides is possible, there have been many cases of resistance. In addition, there is no immediately available biological control method, which means that introduction of Spodoptera spp. could require insecticide treatments that might interfere with existing biological control of other pests.
Source of information
See further information here:
Author: Christiane Scheel
Editor: Elise T. Yamamoto Buch