Over this past holiday weekend, Stalk Borers reached their 1,300-1,400 degree days needed for stalk borers migration to begin. Currently you should be scouting for Stalk Borers in your southern Iowa fields with the migration later in June for central and northern Iowa fields.
Description:
Stalk Borer larvae have three pairs of true legs and four pairs of fleshy prolegs. Young larvae are creamy white with dark purple to brown stripes. Most times there is a creamy white stripe running down the back of the thorax and abdomen. All larvae have a black stripe on each side of their head. A distinctive feature of the stalk borer larvae is an orange head. The adults are dark grey and brown colored moths, with jagged white lines and two to three clusters of white spots.
Photo 1: Stalk Borer Larvae Photo 2: Stalk Borer Moth
Stalk Borers have one generation in Iowa. Stalk borer eggs are laid on grasses and weeds in the fall and they then overwinter in the cold- hardy stage. Stalk Borer eggs will hatch around April 19-June 5, with 50% of the eggs hatching at 494 degree days. The larvae will attack plants from V5 to V10 stage of the corn plant. The larvae will feed on the whorl or burrow of the stalk, sometimes killing the growing point. Emerging/ new leaves often have numerous large holes in a repeating pattern and may be cut completely. Plants that are effected by Stalk borers are often stunted in growth. After V7 stage the Stalk Borer is unlikely to kill the corn plant. When out scouting for Stalk Borer look in the border rows next to grassy areas such as waterways and fence lines. Previous stand loss can be an indicator of future damage in corn on corn rotations. After killing weeds on the borders of fields the larvae will move to the corn plants. Consider tank mixing insecticide with a fast burndown herbicide or spot treating border rows a week after the killing of the weeds.
Photo 3: Stalk Borer Whorl Damage
