Corn earworm larvae are a common pest of grain sorghum. The larva has alternating light and dark stripes and tiny spines down the length of the body. The color of larvae varies considerably, but the head capsule is a creamy-yellow. Full grown larvae are about 1½ inches long. Corn earworms will feed in the whorls of young plants, like fall armyworm. However, feeding on the kernels of grain heads is more likely to cause economic damage.
Check in the whorls of young plants and the grain heads of older plants. Examine a minimum of 50 plants throughout the field. Sets of 10 heads can be briskly shaken into a bucket or sweep net. Carefully look through the debris for larvae of all sizes. Fall armyworm or sorghum webworm will also be found feeding in heads. Frass (worm poop) often accumulates in the collars of upper leaves if large larvae are present.
Treatment is recommended when an average of one or more larvae is found per plant.
|Insecticide (Trade Names) for CORN EARWORM||Lb Active Ingredient per Acre||Amount Formulation per Acre||Performance Rating|
|carbaryl (Sevin 80S)||1 - 2||1.25 - 2.5 lb||5|
|carbaryl (Sevin XLR 4)||0.5 - 1||16 - 32 oz||5|
|chlorantraniliprole (Prevathon 0.43 SC)||0.05 - 0.07||14 - 20 oz||9|
|chlorantraniliprole, λ-cyhalothrin (Besiege)||See label||6 - 10 oz||9|
|chlorpyrifos (Lorsban 4, Nufos 4)||1||32 oz||5|
|chlorpyrifos (Lorsban Advanced 3.775)||0.94||32 oz||5|
|chlorpyrifos, γ-cyhalothrin (Cobalt Advanced)||See label||16 - 38 oz||7|
|chlorpyrifos, Z-cypermethrin (Stallion)||See label||5 - 11.75 oz||7|
|methomyl (Lannate LV 2.4)||0.45||24 oz||7|
|NPV virus (Heligen) *||See label||1 - 1.4 oz||6|
|spinosad (Blackhawk 36% WDG)||0.038 - 0.074||1.7 - 3.3 oz||6|
|esfenvalerate (Asana XL 0.66) **||0.015 - 0.03||2.9 - 5.8 oz||6|
|β-cyfluthrin (Baythroid XL 1) **||0.01 - 0.02||1.3 - 2.8 oz||6|
|γ-cyhalothrin (Declare 1.25) **||0.01 - 0.015||1.02 - 1.54 oz||6|
|λ-cyhalothrin (Warrior II 2.08) **||0.02 - 0.03||1.23 - 1.85 oz||6|
|Z-cypermethrin (Mustang Max 0.8) **||0.01 - 0.025||1.76 - 4 oz||6|
* NPV virus (Heligen) will only control corn earworm. Applications should be made when larvae are small. Do not apply if most larvae are large or if infestations are well above treatment threshold.
** Corn earworm has developed some level of resistance to pyrethroid insecticides. Thus, they may not provide adequate control. Use another insecticide or tank mix acephate (at least 0.5 lb active ingredient) with a pyrethroid insecticide if infestations are well above the threshold level.
- Planting early, before mid-May, may help avoid some damage from corn earworm and fall armyworm.