Leaf chewers such as grasshoppers, cabbage worms and beetles leave telltale evidence. Insect damage weakens plants, reduces yields and, in some cases, kills plants if left unattended.

Japanese beetles are particularly fond of roses, especially the yellow- or light-colored varieties. They also consume the tender leaves of other plants, and their larvae can damage the roots.

The cucumber beetle is another voracious leaf chewer.

Cutworms feed on a wide range of crops including corn, beans, peppers and tomatoes.

The "honeydew" created by aphids, mealybugs and spider mites establishes an area for a fungus--sooty mold--that starts feeding on the residue. Eventually the area will turn black and the plant will suffer from a lack of photosynthesis.

A web-like residue like this is an indication of spider mites.

Diagnosing Pest Problems

Every year, gardeners spend millions of dollars trying to control insects and diseases. There are some natural ways to deal with pest problems and some gardening practices to help prevent problems. To effectively deal with pests and diseases, you need to pinpoint exactly what's causing the problem.

A garden is actually a natural micro-system at work. A lot of factors are involved in determining what is happening in your garden. If you examine your plants and find ragged, chewed or missing leaves, or holes in stems or branches, insects are the likely culprits. Insect species vary from zone to zone--the climate ultimately dictates which bugs live where.

Bugs can be categorized by the types of damage they wield. Some insects chew on leaves or other parts of the plant, above or below ground. Others damage the plants by sucking the sap out of them.

• Cabbageworms are leaf eaters that concentrate on members of the cabbage family: broccoli, Brussels sprouts, cabbage, cauliflower and kohlrabi.
• Grasshoppers are green or brown, and they're difficult to catch in the act of damaging your plants. Look for ragged feeding holes on the edges of leaves to know they're the ones doing damage.
• Cutworms enjoy vegetable plants underground. If you find a plant cut off at the ground, you probably have cutworms.
• Squash vine borer's larvae bore into the bottom 3 feet of the stem and girdle it. This prevents nutrients from moving up the stem and the plant may suddenly wilt. Squash, zucchini, pumpkins and gourds are favorite targets.
• Slugs and snails leave a trail of slime and holes in leaves. They feast on most plants, especially young, tender transplants.
• Aphids are small, soft-bodied insects that range in color from yellow to red to green. They're found on the underside of leaves and leave a trail of sticky honeydew that attracts fungi.
• Spider mites can also be found on the underside of leaves and cause a yellowing of leaf tissue. You'll find webbing similar to spider webs around the colonies of spider mites on leaves, stems, fruit and houseplants. Large populations can kill leaves and reduce yields.
• Mealybugs can be found on all parts of the plants, but they prefer stem tips and new growth. White, waxy blobs are a sure sign of mealybugs. Leaves that have had their sap sucked out appear deformed, yellow or brown and stunted in growth.
• Spittlebugs leave a white, frothy substance on plants. If you look closely, you'll see tiny black bugs with red eyes and legs. They weaken a plant and cause stunted growth.

Insects can move into your garden and rapidly increase in number. Examine plants at least twice a week throughout the growing season. The best thing you can do is to maintain a healthy garden. Good watering schedules and nutrient levels produce healthy plants that are much more resistant to pests. Also, get rid of pests as soon as you notice them and work at keeping them under control.