Saltmarsh caterpillars and other woolly worms are commonly found in soybean. Larvae feed only on leaves and occasionally cause enough defoliation to justify treatment. The feeding damage is similar to that of other defoliating caterpillars. Eggs are laid in a mass, usually on leaves, and the small, light-colored and somewhat hairy larvae may be found clustered together after hatching. Larger larvae of the saltmarsh caterpillars are hairy and vary considerably in color, although they tend to be white, yellowish, or cream colored when an outbreak occurs. The larvae have four pairs of prolegs and grow to a length exceeding 2 inches.

Saltmarsh caterpillars may be found at any time during the season, but they are most commonly observed after flowering has begun. In an average sized field, take 25 sweeps with a sweep net and count the number of larvae that are found at 4 locations. Increase the number of sampling sites in large fields (> 50 acres). Also, visually estimate percent defoliation at each sampling point. It is important to document what other pests are present and may also be contributing to defoliation.

Treat at 30% defoliation until bloom (R1), 20% from bloom to full seed (R1-R6), and 30% after R6 to R6 plus 7-10 days.

Management options

Insecticide (Trade Names) for SALTMARSH CATERPILLARLb Active Ingredient per AcreAmount Formulation per AcrePerformance Rating
bifenthrin (Brigade 2E, Discipline 2E, Fanfare 2E)0.063 - 0.104 - 6.4 oz6
chlorantraniliprole, bifenthrin (Elevest)See label4.8 - 9.6 oz9
chlorantraniliprole, λ-cyhalothrin (Besiege)See label6 - 8 oz9
esfenvalerate (Asana XL 0.66E)0.015 - 0.032.9 - 5.8 oz6
methoxyfenozide (Intrepid 2)0.063 - 0.1254 - 8 oz8
novaluron (Diamond 0.83E)0.039 - 0.0526 - 9 oz8
permethrin (Arctic 3.2, Pounce 3.2)0.05 - 0.12 - 4 oz6
spinetoram (Radiant SC 1)0.016 - 0.0312 - 4 oz9
spinetoram, methoxyfenozide (Intrepid Edge)See label4 - 6.4 oz9
spinosad (Blackhawk 36% WDG)0.039 - 0.051.7 - 2.2 oz9
β-cyfluthrin (Baythroid XL 1)0.013 - 0.0221.6 - 2.8 oz6
γ-cyhalothrin (Declare 1.25)0.0075 - 0.01250.77 - 1.28 oz6
λ-cyhalothrin (Warrior II 2.08)0.015 - 0.0250.96 - 1.6 oz6
Z-cypermethrin (Mustang Maxx 0.8E)0.0175 - 0.0252.8 - 4 oz6
  • A naturally occurring fungus that attacks saltmarsh caterpillars will sometimes quickly reduce infestation levels.