Crop Profile for Strawberries in California - Regional IPM Centers

Monitoring. When monitoring for other pests, growers watch for evidence of looper feeding: leaflets
with holes, feces, and caterpillars feeding at the edge of a hole. If larvae are larger instars, an
organophosphate may be needed to control them.
Cultural:
Controls
● Placement of Fields Relative to Other Crops. Cabbage looper has only recently become a pest
in strawberries planted next to lettuce fields. Selecting a strawberry field that is not adjacent to a
host crop for cabbage looper is one way to control infestations, although this practice has become
less practical due to rotation with vegetable growers.
Biological:
● Parasitic Wasps. Loopers are sometimes controlled by the parasitic wasps Hyposoter exiguae,
Copidosoma truncatellum, and Trichogramma spp.
● Natural Virus. A natural outbreak of nuclear polyhedrosis virus also sometimes provides control
of the looper population.
Chemical:
● Bacillus thuringiensis. 0 day PHI. Bacillus thuringiensis (Bt) is applied at label rates to
approximately 0.1 lb ai/acre on to about 30% of the strawberry acreage. Applications are made
when plants are dry, and 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.
The restricted-entry interval for Bt is 4 hours.
● Diazinon. 5 days PHI. Diazinon is applied to strawberry fields at a rate of 0.8 lb ai/acre.
Diazinon is not used unless loopers pose a serious threat to the crop. Diazinon is harmful to mite
predators and outbreaks of twospotted spider mites may occur following its use. Diazinon is used
to treat around 8% the state's strawberry acres. The restricted-entry interval for diazinon is 24
hours.
● Chlorpyrifos. 21 day PHI. Chlorpyrifos (LORSBAN) is an broad-spectrum insecticide applied at
an average rate of 1 lb ai/acre to approximately 15% of strawberry acreage. Applications are
typically made pre-bloom. Chlorpyrifos provides economic control but kills beneficial and
nontarget organisms. The restricted-entry interval for chlorpyrifos is 24 hours.
● Methomyl. 3 day PHI for fresh and 10 day PHI for processing strawberries. Methomyl