The Imported Cabbageworm
The gardening season is starting to wind down and will finish with hard frosts in the coming weeks (unless you are using some season extension technology). But even though the amount of harvest may be less than the late summer months, we still have some fresh produce yet to grace our tables. The cole crops such as broccoli, cabbage, and cauliflower may still need to few weeks of growth to reach maturity (depending on when you planted) and gardeners need to remain vigilant.
One of the more common pests is the imported cabbageworm. One can guess that it is not from around these parts but has been present in the US since the late 1800s. Their feeding activity can create several problems for both commercial growers and home gardeners.
The immature stage (larva) are voracious feeders and eat all the foliage to where only the stems and veins remain. A large leaf area is needed to capture sunlight and provide the sugars for plant growth. Reduced leaf material results in reduced heads (i.e. smaller cabbage or broccoli heads).
In addition, the ravenous appetite of the cabbageworms results in a lot of fecal matter (what goes in, something has to come out). While some of the fecal pellets may fall to the ground, much of it remains on the leaves or harvestable portion. Want to turn off a child’s interest in vegetables? Show them broccoli that has fecal matter all over it.
Finally, there are times when the cabbageworm larva may burrow in the broccoli or cabbage head. Not only could you scar your kids with the appearance of fecal matter, but biting down on a worm would be enough to push them over the edge and lead to a fear of fresh vegetables for life.
There are several ways to manages this pest. If you notice some leaves that have small smooth (not jagged edges) feeding holes, then it is time to hunt. Hand-pick the larvae and crush underfoot.
The adult is a butterfly with white wings with black dots in the central area. The female flies about looking for places, such as cabbage leaves, to lay her eggs. Covering the crop with row covers to exclude the flying female does a pretty good job of preventing an interaction between egg laying adult and the host plant.
And of course, there are a multitude of insecticides that can control the larvae. These run the gamut of organic products that contain Bacillus thuringiensis, neem, Spinosad, or pyrethrum to the conventional products such as carbaryl (i.e. Sevin).