Beet armyworm or small mottled willow moth Spodoptera exigua Hbn.
It damages more than 120 crops: tomatoes, potatoes, cotton, corn, soybeans, vegetables, peas, eggplant, apple, quince, acacia, oak, weed species, etc.
It overwinters as pupae in the soil. In Bulgaria it develops 3–4 generations per year. Butterflies fly from May to November. A female lays 500–2000 eggs.
The eggs are laid in groups of 5–20–50 to 250 on the underside of the leaves and cover the eggs with hairs detached from the female’s abdomen. Do not cover the eggs immediately, but 1–2.5 hours after laying. 1st generation caterpillars develop on weeds and alfalfa. The second and subsequent generations damage generative organs, ears of corn, cob of sunflower, fruit of vegetables, etc. Trichogramma displacement should occur 1–3 days before the start of laying. This way the trichogramma will be able to parasitize them before the female butterfly covers them with hairs.
Displacement of trichogramma — same as other bollworms, the important thing is in which areas. Under conditions favourable for the trichogramma, the HTC =0.9–1.2.
Where HTC =0.5–0.8 or 1.3–1.7, lower efficiency is expected. Only the species T. evanescens should be used. We emphasise that when trichogramma is sown in private vegetable gardens, sowing should be at least 400 points per hectare in a 5×5 m scheme. Trichogramma should only be sown in the morning or in the evening. It is active between 7:00–11:00 and from 16:00–20:00.
Pheromone traps for determining the rate and timing of displacement. Two–three days after capturing 3–4 male butterflies /catch for the first generation and 7–9 for the second, a trichogramma is made to disperse.