Common Name: Diamondback moth
Latin Name: Plutella xylostella
Main Host(s): Cole crops (cruciferous plants)
Diamondback Moths occur worldwide, but populations are sparse in cold climates. Diamondback Moth larvae are relatively small — about one-third of an inch when full grown — compared to other caterpillars found in Brassica vegetable crops, Their rapid 30-day life cycle can cause serious crop damage.
This pest has many generations per year, five to seven in moderately warm climates with an even higher number in (sub)-tropical regions. Diamondback Moth generations can quickly start overlapping, especially in warmer climates, meaning that eggs, larvae, and pupae can all be found in the same field at the same time.
Females will lay about 100 eggs over a two-day period, generally on the undersides of leaves. The eggs will hatch in five to six days and four larval stages follow, which combined, last between 21-25 days. The larvae will initially burrow into the leaf and mine it during the first and second instars. Then, toward the end of the second larval stage, it will exit and start feeding on the underside of the leaf. Pupa can be found in small cocoons attached to leaf surfaces.
Impact & Damage
The Diamondback Moth has developed resistance to more than 40 insecticides since the 1960s, with the demonstrated ability to develop insecticide resistance in only 2-4 years. It has done so especially in tropical countries such as Malaysia, Taiwan, Thailand, etc., where Brassica crops are grown in a continuous cropping cycle. This makes DBM a perfect target for an integrated control program featuring biorational products.
Close scouting of the fields, followed by pinpoint applications of DiPel® or XenTari® and using a rotation of chemical insecticides, should provide an effective IPM program that avoids problems with resistance. As with most pests controlled by Bt, it’s best to control the Diamondback Moth in its early larval stages. Since feeding begins on the underside of the leaves, it’s critical that the spray application fully covers the foliage. It’s typically best to use sex pheromone traps to predict moth population peaks and is critical to begin applications when larvae are young before the pest reaches older larval stages.
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