The Corn Rootworm – Virtually Everywhere!

North, South and West: we always thought them as nothing more than the cardinal directions, but actually they are also these directions also lend their name to three different kinds of a unique beetle known as the corn rootworm! Famous for feeding solely on corn crops, they are most commonly found in the United States, predominantly in the state of Iowa, the region’s largest corn producer.

Among the first misconceptions about these creatures is the fact that they feed only on corn throughout their lifetime, thereby destroying mature crops and causing large amounts of damage. What is actually interesting to find out is the fact that both the Northern and Western species tend to feed less on corn and more on the pollen and flowers of other plants as the corn tends to mature. Though, of course, the corn crop is still affected, but perhaps the effect is not as pronounced as we are told. In the event the rootworm matures before the corn crop, the adults will leave the corn alone and tend to feed only on the leaves instead. This information is useful, since farmers can observe the life-cycle of the corn rootworm and plant their crops in a manner that ensures they will grow before the adults are able to emerge! Indeed, most farmers engage in crop rotation for this very reason.

The corn rootworms are very small creatures – much like most beetles – with the adults being only a quarter of an inch long. The differences between the Western and Northern species is very pronounced though; the former tend to be yellowish with a single black stripe on each wing cover, while the latter vary between solid color shades of light tan to pale green. In either case, the beetles are relatively easy to identify, provided one can observe them!

Like beetles such as the Emerald Ash Borer, the corn rootworm life-cycle also depends greatly on the location the egg is laid in, as well as the temperature of the region. The eggs lay by the female are very minute – only 0.1 millimeter long – and are shaped like an American football. Preferring colder temperatures to grow in, the eggs are normally deposited in the winters, roughly 8 millimeters under the soil. In some cases, this depth can increase depending on how dry the soil is, and also how if it is colder than the normal temperature in order to create a better insulating layer around the tiny eggs. The males are quicker to emerge than the females, but both the genders are fully thriving in the months of July and August when the temperatures are warmer and conducive to feeding. The emergence of the adults continues for almost a month from the time it starts, which is a very long period of time for such a small creature!

People often tend to overlook how fascinating these creatures can be because they’re too busy looking for ways to avoid them. However, there is actually a lot more to them than meets the eye. Only one question remains though: is there an Eastern corn rootworm species to complete all the compass directions?