Consider Options to Control Common Stalk Borer

If you lose corn plants along the edge of a field next to grassy borders, you may have common stalk borer.

"If you have problems with common stalk borer eating your corn plants along the edges of fields near grassed field borders or terraces or buffer strips, consider option 1 in early April to control this insect pest," suggests Brian Lang, an Iowa State University Extension field agronomist at Decorah in northeast Iowa.

He suggests you go to the following Web site for photos of the problem: www.ipm.iastate.edu/ipm/icm/1997/4-7-1997/toastsborer.html  

Common stalk borer has basically five timing periods for management to reduce either "field border" problems, or "in-field" infestations, says Lang. The five options are:

* Option 1. Burn grassy road ditches, grass-back terraces, etc. to reduce "field border" infestations. The recommended time to burn the grass is when the new grass growth is beginning to spike. This timing usually starts in mid-to-late March, but will be a little later this spring. This will kill the eggs laid last fall. Actually the grass could have been burned at any time from late fall until now, but spring is the preferred time to minimize exposure to soil erosion.

However, there are some precautions to take:

1) If roadside crews have established native plantings in your road ditches, it would be harmful to burn these plantings in fall or spring.
2) Be aware of roadside utilities (gas, electrical, communications) that could be damaged and be held liable for.
3) Much of the area is still drier than normal, and makes a roadside fire easy to get out of hand.
4) Be careful of other trash in ditches (discarded oil or gas cans, broken glass, etc.)

* Option 2. Apply insecticide during egg hatch, that is 575 to 750 DD (base 41, Jan. 1). "We will track degree days and let you know when we approach these numbers," he says.

* Option 3. Apply insecticide with "in-field" herbicide program if perennial grasses and ragweed (populations from last year) are extensive. If larva are in these weeds (quackgrass, wirestem, and giant ragweed) when the weeds are killed with postemergence herbicide, the larva are forced to move out of the weed and into something else (such as corn plants).

* Option 4. For "field border" infestations, if no previous method was used, apply insecticide during larvae migration that is 1,100 to 1,400 DD (base 41, Jan. 1). Larva too large for a grass stem, leave the grass at this time to find a larger plant to live in (i.e. corn).

"Timing to apply an insecticide at this time along the field border and the first rows of corn next to the field border will catch many of the migrating larvae. This usually occurs in mid-June, but we will track the degree days," says Lang.

* Option 5. Moldboard or chisel plow tillage will bury eggs deep enough in the soil so that many of the hatched larvae do not survive. Be careful not to cause soil erosion if you choose to use this tillage option, says Lang.

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