Diamondback Moth, Plutella xylostella
(Lepidoptera: Plutellidae)

The diamondback moth is distributed throughout the Americas and is recorded everywhere that cabbage is grown. The total development time is 25 to 30 days depending on weather. Eggs are oval and flattened and are yellow or pale green. Eggs may be deposited singly or in small groups. Larvae are quite small and if disturbed will wiggle violently, move backward, and spin down from the plant on a strand of silk. The body of the larva tapers at both ends and a pair of prolegs protrudes from the posterior end forming a distinctive “V.” The larvae are first colorless and then later become green. The body has very few hairs. A small silk cocoon is formed on the lower or outer leaves and a yellow pupa is formed. The adult is small and grayish-brown with long antennae. The adult has a broad light brown band around the back. When viewed from the side, the tips of the wings turn upwards slightly. The diamondback moth attacks only plants in the family Cruciferae (cabbage and its relatives).

Vegetable crops that are eaten include broccoli, Brussels sprouts, cabbage, cauliflower, collard, mustard, radish, turnip, and watercress. Cruciferous weeds are important alternate hosts early in the season. Larval feeding causes plant damage. The larvae remove foliage tissue except for leaf veins and can be very damaging to seedlings and may disrupt head formation in cabbage. Sampling for diamondback moth is accomplished by making counts of larvae or by the level of damage seen. Some economic thresholds are established. Natural enemies are present in the field but insecticides are usually applied in order to manage populations in the field. Resistance to insecticides is a serious problem. Some strains of Bacillus thuringiensis are used effectively. Cultural practices may also be used, such as host plant resistance, crop diversity, crop rotation, planting clean transplants, and the removal of alternate weed hosts. Recently, a pheromone for mating disruption has become available.

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Diamondback moth, Plutella xylostella, adult.
(Photographer: J. Castner, University of Florida)

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Diamondback moth, Plutella xylostella, adult.
(Photographer: L. Buss, University of Florida)

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Diamondback moth, Plutella xylostella, pupal case.
(Photographer: L. Buss, University of Florida)

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Diamondback moth, Plutella xylostella, larva.
(Photographer: J. Castner, University of Florida)

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Diamondback moth, Plutella xylostella, mature larva
and feeding damage.
(Photographer: P. Choate, University of Florida)

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