MANAGEMENT OF DIAMONDBACK MOTH*
Management of Diamondback moth populations depends on culture
practices, the use of chemical and biological sprays and
monitoring. A host-free period can help to reduce Diamondback
moth levels after final harvest of the current season's crop; the
longer the host-free period, the greater the reduction in
Diamondback moth population. A host-free period is when old
plantings have been disked under and other infestation areas such
as greenhouse seedlings or alternate hosts have not been present
to support Diamondback moth populations. All crop residue should
be disked to a depth of at least 2 to 4 inches, immediately after
harvest is complete, to destroy larval food sources and pupae in
the soil. Wherever possible, destroy infested crops before a new
crop is planted in adjacent fields. Transplants also must be
checked before planting as field infestations can occur from
infested transplants. This product may be used in an IPM program
in conjunction with insecticides in areas of high pressure, where
migration from adjoining fields is occurring, or where control of
secondary pests is needed.
*Integrated Pest Management for Cole Crops, University of
California
DIAMONDBACK MOTH
BIOLOGY
Diamondback larvae are small (about 0.33 inch when full grown)
compared to other caterpillars in cole crops. The larval body is
wider in the middle and tapering at both ends with two pro-legs
on the last segment forming a distinctive V-shape at the rear
end. When disturbed the larvae wiggle frantically or rapidly
attach a silken line to a leaf and drop over the edge. They feed
mostly on outer or older leaves of older plants chewing out small
holes or at the growing points of young plants. They will also
feed on floral stalks and flower buds. Larvae mature in 10 to 14
days and spin a loose cocoon on leaves or stems for pupation.
Moths lay their tiny, roundish eggs singly on the undersides of
leaves; eggs are difficult to find. Although they may occur all
year round diamondback moths are often abundant in spring and
early summer and populations may rise again in fall.
DAMAGE:
Diamondback moth infestations are most serious when they damage
the crowns or growing points of young plants or Brussels sprouts.
This injury can severely stunt growth. Sometimes diamondback moth
caterpillars may also bore into heads of broccoli or cauliflower,
or in the flower buds of stalks, causing economic injury and
contamination. Injury to leaves is not usually serious, except
when the wrapper or cap leaves of cabbage are injured.
BIOLOGICAL CONTROL:
Natural enemies can provide some control of Diamondback moth. In
Southern California, the ichneumonid wasp, Diadegma insularis,
has been identified as the most common parasite. Trichogramma
pretiosum may also attack diamondback eggs. Microbial diseases
are not known to be a significant mortality factor. |
