Crop Profile for Strawberries in California - Regional IPM Centers

crowns of young plants, killing them. Young larvae feed on foliage before attacking berries. Larger
armyworms feed directly into the berries. Smaller armyworms will often feed on the shoulder of the
berry.
Description of Pest. Fall populations of armyworm moths will often fly into strawberry fields to lay
eggs. Newly hatched armyworms are often green in color and feed in groups, skeletonizing the
undersides of leaves.
Monitoring. Treatments are made while armyworms are still young. If large numbers of predators are
present, treatments may be delayed to determine if the armyworms might be controlled by the natural
enemies.
Cultural:
Controls
● Weed Control. Growers control weeds in and near the field to minimize armyworm populations,
as adult moths are attracted to weeds for egg laying.
Biological:
● Hyposoter exiguae. Young beet armyworms can be heavily parasitized by the ichneumonid
parasite, Hyposoter exiguae. This parasite is easily monitored in the armyworm populations by
simply pulling young worms apart and looking for the parasite larva inside.
● Natural Virus. Armyworms often become diseased with a virus that can cause high mortality.
High natural mortality translates to few mature larvae surviving to cause further damage.
Chemical:
● Bacillus Thuringiensis, subsp. aizawai. 0 day PHI. Bacillus thuringiensis (Bt) is applied at rates
of 0.1 lb ai/acre and is the best subspecies for controlling beet armyworm. About 30% of the
state's acreage is treated with Bt. Good coverage at relatively low dilution rates is essential to
product performance. Bt treatments are made when armyworms are still small. For Bt to be
effective it must be applied no later than the second instar. Bt is acceptable for use on organically
grown produce. There is a 4 hour restricted-entry interval for Bt.
● Bacillus Thuringiensis, subsp. kurstaki. 0 day PHI. Bacillus thuringiensis (Bt) is applied at 0.1
lb ai/acre of strawberry. Bt applications are made onto about 30% of the state's acreage. Good
coverage at relatively low dilution rates is essential to product performance. Treatments are made
when armyworms are still small. To be effective it must be applied no later than the second
instar. Bt is acceptable for use on organically grown produce. There is a 4 hour restricted-entry