Hop Vine Borer

Injury and Symptoms

Larvae tunnel upward from the bottom of the stalk; injury is confined
to below-ground portions of stalk (see yellow arrows above)
Tunneling usually kills the plant
Infestations in corn are associated with:
- areas of grassy weeds
- field edges, terraces, or waterways where perennial grasses occur
- no-till or conservation-till fields with poor grass control the previous year
- continuous corn production and poor grass control

Common name: hop vine borer
Latin name: Hydraecia immanis, family Noctuidae
Description
- Adult: dull brown moth with buff-colored front forewings and dull-white hind wings; wingspan 1½ inches
- Larva: solid orange or reddish-brown head with black eyes; large dark purple or brown spots, almost square-shaped, along the back with transverse rows along the side, and separated by contrasting dirty white lines
- Egg: brown and oval, often laid in parallel rows, hidden under dried grass leaves and sheaths

Origin and distribution:
- Native to North America
- Central and eastern Corn Belt from western Iowa to southern Ohio and New York
Similar species:
- Potato stem borer, which is light red or pink, occurs mostly north of the Great Lakes and in the St. Lawrence River Valley

Pest Status and Importance

Occasional or rare pest of early vegetative corn
Stand loss is possible in areas of grassy weeds
Damage mostly reported from northern Illinois, northeastern Iowa, southeastern Minnesota and southern Wisconsin

One generation per year
Overwintered eggs hatch in late April and early May
Larvae have six, or occasionally seven, stages
First-stage larvae tunnel into grass stems such as smooth brome grass, quackgrass, orchard grass, woolly cupgrass, and wirestem muhly
Third- and fourth-stage larvae outgrow grass stems and move to corn
Large larvae prefer only corn and hops
Larvae pupate in the soil in early July
Adults emerge during late July and August
Females lay eggs on grasses

Weed management
- Do not allow grassy weeds to proliferate in corn
- Eliminate grassy weeds before late summer to remove egg-laying sites
Insecticides
- Broad spectrum insecticides labeled for cutworms may provide control, but only if applied at corn emergence and before larvae tunnel into the stem
Insecticide seed treatments
- Seed treatments are not labeled for this insect
Bt corn
- Products containing Cry1Ab or Cry1F traits are not labeled for this insect

Photos and Text
Marlin E. Rice, DuPont Pioneer
Reviewed by Herb Eichenseer and Paula Davis (Pioneer)