We wait a long time in Montana to enjoy the first corn of the season. I dont know anyone locally who’s harvesting yet and we’re quickly approaching Labor Day. So when we finally are able to pick fresh sweet corn, we don’t want to find yicky little corn pests. While we do have the occasional earwig that ruins the corn, we dont have some of the most problematic pests found in other parts of the country. Here are some of the worst ones:

European Corn Borer

This one is tough because it’s so prevalent. The larvae overwinters in the stubble of corn, oftentimes within the bottom 6 inches of the stalk, which is why it’s so important to clean up the garden after harvest.

European Corn Borers emerge in the spring as adults, and the female moths lay eggs on the undersides of the leaves at night. The newly hatched larvae feed on tassles and corn silk to start, but they do the most damage when they burrow into the ears themselves. The challenge with ECBs is there are often 2 generations in mild climates so you have to maintain diligence.

You can hit the corn with spinosad or cyfluthrin (a synthetic pyrethroid) shortly after tassling, but many farmers and gardeners live with a certain amount of damage unless there is roughly 10% affected. The best course of action is to keep rotating the planting space, and thoroughly clearing the stubble to eliminate them while theyre dormant.

Corn Pests: Earworms

Here is another that is highly destructive, probably more so than the European Core Borer. It has a very different lifecycle in northern states than ECB because it doesnt overwinter in cold climates; instead, the adult moths fly up to infest fields. Where they do overwinter, the problem is even worse.

Corn earworm adult moths lay between 500 to 3,000 eggs in the silks of the corn, then the larvae burrows down into the top part of the corn. The only good thing is when you peel it back you can normally snap off the area and toss it out. Because it appears corn earworms are developing a certain amount of resistance to efficacy of many insecticides, treatment with chemicals is sketchy. If your corn patch is small enough you could apply mineral oil to the silks after pollination can knock down the numbers considerably.

Fall Armyworms

While I’m an advocate of planting for late season harvests, this is precisely when the fall armyworm does a lot of damage. They overwinter in the Gulf States and Florida, then adults migrate to the north. Theyre found practically everywhere except in the Rocky Mountains.

You know any garden pest with the word army in its name can’t be good. The armyworms march northward, defoliating plants as they go. They prefer species in the grass family, which corn is a prime selection, but will also feast on tomatoes and other vegetable plants. (They’ll also riddle lawns with large patches of dead turf. It drives my lawn loving friends crazy.)

If there is serious damage you can use Sevin (carbaryl) or Spinosad. The trouble is, it often requires 4 treatments per week to keep up so you have to decide how much damage youre willing to live with before resorting to chemical measures.

Corn is one of the vegetables best enjoyed right out of the garden, and we look forward to it so much during the year that a couple of worms wont ruin the fun. But, when there are enough to fill the USDA protein requirements, we have to draw the line!