Cabbage Integrated Pest Management : An Ecological Guide.

Major Cabbage Insect Pestsinstars feed in groups on the leaves of plants, the thirdinstar becomes solitary and becomes a real cutworm(sometimes even has cannibalistic habits). The pupa ofthe black cutworm is dark red-brown and about 20 mmlong. Pupation takes 10 - 30 days depending ontemperature. Adults are large, dark moths with a wingspanof 40 - 50 mm, with a gray body. Forewings are palebrown in color with a dark brown-black pattern of markings.The hindwings are almost white but with a dark terminalline.In warm conditions, there can be 5 generations or more,depending on the temperature. Life cycle from egg toadult takes 32 days at 30 o C, 41 days at 26 o C and 67days at 20 o C.Agrotis ipsilon(Stoll, 1987)The caterpillar of the common cutworm (Agrotis segetum)is gray-brown and about 30 - 40 mm long when mature. It has faint dark lines along the sides of the body.The larval body is plump and rather greasy in appearance. The pupa is smooth shiny brown to red-brownwith two spines at the rear, about 15 - 20 mm long. Pupation takes place in the soil.Adult moths are usually smaller than the adults of the black cutworm. They measure 30 - 40 mm acrossthe wings, the forewing is gray-brown in color with a dark brown kidney-shaped marking. The hindwingsare almost white in the male but darker in the female. The body and head of the adult are brown in color.Life cycleAdult moths fly at night and can cover large distances. Female moths lay many eggs (up to 1200). Theeggs are laid singly or in small groups around the base of host plants or on leaves or stems, and onweeds or plant debris in the field. Eggs are ribbed, about 0.5 mm in diameter and pale yellow in color atfirst, later turning cream-colored to brown. The eggs of Agrotis ipsilon have reddish-yellow markings. Theeggs hatch in 3 to 25 days, depending on the temperature. At 25 o C for example, the eggs hatch in 3-4days. The first instar larvae feed on the leaves of the host plants and when larger, they go down to the soiland adopt typical cutworm feeding habits. There are usually five to six larval instars. Fully grown larvaepupate as deep as 12 cm in the soil. Pupation lasts 10 to 30 days, depending on the temperature.Cutworms can survive only where the soil is dry. Temperatures above 35 o C will kill the insects.Plant damageDamage to seedlings and young plants can be very serious. During the day, cutworms hide in the surfacelayers of the soil, under leaves or stones. At night, the larvae come to the soil surface and feed on plantstems at ground level. The stem may becompletely hollowed out just below soillevel or cut through at soil level. Typicaldamage is for the cutworm to move alongthe row of seedlings cutting each onethrough the stem at ground level. Cutwormdamage is most severe in light, sandysoils where the larvae can burrow easily.89 Cabbage Ecological Guide - 2000