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Entomology: Insects Associated With Vegetable Crops in Georgia: Cole Crops

Webworm

(Order: Lepidoptera, Family: Pyralidae)
Cabbage
(Hellula rogatalis (Hulst))
Oriental Cabbage
(Hellula undalis (Fabricius))

Description:

Cabbage webworm and
feeding damage to leaf.

Adult: 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 down the forewing. Both of the above species match this description.
Immature 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 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.
Seasonal distribution: In Georgia, we have observed damaging levels of this pest only in the summer and fall growing seasons.

 
Webworm damage to
terminal growing point.

Damage to Crop: Early instars begin feeding in mines in the terminal leaves of greens and in cabbage in the center whorl where the head will develop. Later instars cause 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 and plant deformation in greens. 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 0.3 larvae per plant should be tolerated. However, specifically for webworm because of their unique damage to the growing point, the threshold is typically lowered to presence of larvae if an 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.

Return to Vegetable Crops

Prepared by Dr. Alton “Stormy” Sparks, Jr. and Dr. David G. Riley - University of Georgia

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