Hellula, rogatalis
Or Oriental cabbage webworm (Hellula, unadalis).
Authors: David Riley and Stormy Sparks, Extension Entomologists, University of Georgia, 2018
Description
Immature stages: The eggs are flattened, 0.3 mm wide by 0.5 mm long, and are laid singly or in small groups on terminal leaves. The mature larvae are yellowish gray with five brownish-purplish bands running down the length of the larva. Late instar larvae are typically associated with webbing of the leaves.
Adult stages: The moderately sized adults (18-21 mm wingspan) have yellowish brown wings marked with white bands and a dark, kidney shaped spot about two thirds the way down the forewing. Both of the above species match this description.
Biology
Life Cycle: The duration from egg to adult is approximately one month under warm conditions (30°C) with the development time of larvae, the damaging stages, at two weeks. The fifth instar larva forms a webbed cocoon in the soil, pupates and then the adult emerges about six days later.
Distribution: In Georgia, we have observed damaging levels of this pest only in the summer and fall growing seasons.
Damage
Early instars begin feeding in mines in the terminal leaves, in cabbage the center whorl where the head will develop, and by the later instars, causes extensive foliar damage and webbing of leaves. Since the damage is directed at the growing point of the Cole crop, damage to the apical meristem can cause unmarketable, multiple heads in cabbage. Thus, early season damage can be equivalent to a lost plant for each plant infested.
Management
As with other Lepidoptera larval pests in Cole crops, no greater than 0.1-0.3 larvae per plant should be tolerated. However, specifically for webworm because of their unique damage to the growing point, the threshold could be lowered to presence of larvae per plant if a large influx of this pest occurs in cabbage early in the growing season. If webworm appear before the five-leaf stage in cabbage, then a spray treatment is warranted. Usually, standard scouting and control practices for the other Lepidoptera result in satisfactory control of this pest.