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It’s time to scout for corn insects

My father used to tell me that anything would eat corn. He was speaking of animals on the farm and corn on the cob. Sometimes it seems like every insect will eat corn when given the chance as well.

Here’s the list of insects I have had to identify in corn fields over the years: Corn earworms, armyworms, wireworms, billbugs, stinkbugs, seed corn maggots, cutworms and flea beetles. Actually, I have left out a few in the interest of saving space and time.

Fortunately, seed treatments and soil insecticides offer today’s corn growers some excellent defenses against many of these pests. But if despite your best efforts something is damaging your seedling corn plants, how can you tell which pest is to blame? Let’s take a look at the symptoms and start matching them to the offenders.

Corn plants keep their growing points underground for weeks after planting. If the newest leaf blade appears lifeless but the rest of the seedling looks fine then something has damaged the growing point. Dig up the plant and look just below the soil line.

The three most likely culprits are: Billbugs, wireworms, and small cutworms. Billbugs feed at the growing point, and left untreated, parasitize plants with a small, translucent, kidney shaped egg deposited in the growing point. Wireworms and small cutworms may also attack the same point, but their symptoms are normally slightly different.

Wireworms are short stiff beetle larvae that remind some people of copper wire. They often attack the seed kernels. They can kill corn plants. Often in severe infestations multiple wireworms can be found attacking a single plant.

Cutworms usually are true to their name and actually cut plants off at the soil surface. They then pull the cut plant partially under the soil and feed. At times two or three plants will be cut in a row.

Other pests are harder to diagnose. If your corn seedlings appear stunted but the growing point appears undamaged, then you may have seed corn maggots. These pests can ruin seed kernels while the seedlings are still drawing nutrients from them. Seed corn maggots are difficult to see without magnification. With a hand lens examine any soft seed for tiny clear maggots inside the kernels.

Flea beetles can also make corn plants appear generally unhealthy. These tiny black beetles attack the surface of corn leaves and sometimes infect seedlings with bacterial diseases that cause stunting and death.

TAGS: Corn
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