At this time of the year homeowners have more questions about insects than any other subject. “What is that insect? What should I do about it? How can I control it?”
The identification of the pest can be of primary importance, yet there are a hundred ways of categorizing insects. Few individuals have the time or interest to follow the paths laid out by the entomologist of classes, orders, families, genera and species.
Currently there are more than 750,000 species of insects registered and more are discovered daily. In addition, it should be noted that not all garden pests are insects, for example, snails, spiders, millipedes and centipedes.
How do gardeners cope with pests in the garden when the pests are so diverse? One means is to look at the plants that are being fed upon. Potato bugs feed on the foliage of potatoes, bean beetles on beans, corn earworms on corn, cucumber beetles, cabbageworms, squash bugs, each cause feeding damage primarily to a specific kind of plant.
Note, however, that some insects recognize plants that are closely related. For example, both Swiss chard and beets are susceptible to mining by the same leaf minor. Cabbage, broccoli, cauliflower, Brussels sprouts and kale all belong to the same family and thus are troubled by the same insects and diseases.
Then we have the insects that are generalists. Aphids and whiteflies treat almost all plants as if they are fit to eat if the foliage is soft and succulent. Some insects are unseen (active underground) until the harm to the plant is done. June bugs (large, clumsy, flying beetles often heard hitting against storm door screens on summer evenings) and various kinds of chafer beetles (brown beetles clustered together on weed stalks) both are destructive to grass root systems in their young (larva) stage. After they pupate (change from a larva to an adult beetle in a cocoon), June bugs and chafers do little harm.
Another beetle that feeds on grass roots that also feeds on flowers and foliage in its adult stage is the Japanese beetle. In their moth or butterfly stage, no feeding is done. It is the caterpillar growth phase when plant foliage is eaten. No general statements can be made concerning the development stages of insects, as nature seems to have covered all eventualities.
To caution students that all insects are not harmful, they speak of the “doorknob” principle, which states that just because an insect is seen on a doorknob, it does not mean that the insect is feeding on the doorknob. It may simply be resting. Do not automatically assume that every insect is harmful - most are not.
When considering insect control with chemicals, consider that if the material will kill an insect it has a potential for hazard to the environment and all other life forms. Decide if the insect needs to be controlled, use the least hazardous means (hand picking?), and, if using a pesticide, read, understand and follow all instructions.