1. Aphids These tiny pests cause damage by sucking the juices from the leaves and stems of plants, and spreading disease while they do so. They are fairly easy to get rid of -- sometimes all it takes is a strong blast from your hose to knock them off of the plant.
Common Vegetable Garden Insect Pests
2. Asparagus Beetle If those eagerly-awaited stalks of tender asparagus are showing brown spots, scarring, or are bent, asparagus beetles are probably to blame. One of their main predators is a parasitic wasp -- another reason you don't want to use broad spectrum pesticides in your yard. In addition to encouraging the wasps, you can also handpick the larvae, eggs, and beetles from your plants.
3. Cabbage Worm You know those pretty white butterflies you see hovering around your garden in early summer? Yeah. You may want to start checking your cabbage, kale, broccoli and other cruciferous veggies for holes in the leaves. Look underneath, because most likely the culprit is a light green larva that hatches from the eggs deposited by those pretty white butterflies. One of the easiest ways to control them (besides covering your crops with floating row covers and eliminating the problem all together) is to hand pick them and drop them in a cup of soapy water.
4. Colorado Potato Beetle If the foliage on your potato plants is starting to get chewed, chances are good that you have a potato beetle problem. A little work and vigilance, and you can still protect your potato crop. Colorado Potato Beetles overwinter in the soil, so crop rotation can be a huge help in reducing the damage your garden sustains.
5. Corn Borer/Corn Earworm Not just corn, but also peppers, beans, and potatoes can fall victim to corn borers. If any of these plants start toppling over, chances are good that a corn borer has made its way into the stem. Bacillus thuringiensis is an effective natural control for these pests.
6. Cucumber Beetle Besides gnawing on the leaves and fruits, cucumber beetles also spread bacterial wilts. Handpicking is a great option here, as are floating row covers to provide a barrier to these pests in the first place.
7. Cutworm So, you planted out a bunch of perfect tomato seedlings only to find them toppled over, as if chopped down by tiny axes, the next morning. You have a cutworm problem.You can make simple collars from empty toilet paper rolls to protect the stems until they are too large to sustain damage from cutworms. The rolls will break down in the soil, or you can compost them.
8. Flea Beetle Tiny holes in the leaves of eggplants, peppers, radishes, pumpkins and squashes, melons, or tomatoes ( as well as other plants) are a sure sign of flea beetles. While the photo shows a gold-colored flea beetle, they are also often shiny black beetles. You will see them hopping around on the plants like, well, fleas.
9. Mexican Bean Beetle It's late summer, and the foliage on your beans is reduced to almost nothing but the veins. Look under any remaining leaves, and you'll probably find a Mexican bean beetle larva or two. Mexican Bean Beetles are found just about everywhere in the U.S.
10. Slugs The main crop that slugs damage in most gardens is lettuce. These slimy pests just can't get enough of my Amish Deertongue lettuce. Happily, they're fairly easy to get rid of. You can hand pick and squish them, handpick and throw them into a bucket of soapy water, let them drown in some beer, or use a grapefruit rind to trap them.
11. Squash Bug Yellow spots on the leaves of your pumpkins, winter squash, or summer squash are one sign of squash bugs. Another is wilting vines, or vines that wither and turn black. It can be a bit confusing, because the symptoms (wilting vines) are easily confused with that of squash vine borer (below). One good way to determine the difference is to look for dusty looking frass (dropping) on the stems -- that's usually an indicator of vine borer rather than squash bugs.
12. Squash Vine Borer Your perfectly healthy zucchini or pumpkin has a withered vine here and there. Cut open the vine just about where the problem starts, and you'll probably find the grayish-white larva known as squash vine borer. The good news is that once you find them, you can halt the damage. Simply slice the vine open and dig the borer out. Then you can trim off any yellow or wilted parts of the stem, and bury the rest in the soil. It will grow new roots, and keep growing happily
13. Tomato Hornworm Hornworms have voracious appetites. If you find that your perfect tomato suddenly looks like it became an all-you-can-eat buffet, the culprit is most likely hornworms (who have no problem eating either the leaves of fruits of tomato plants.) Most of the above information was written either by myself or insect expert Debbie Hadley, who is a colleague of mine at About.com. I hope the photos, descriptions of damage, and organic control options outlined in each article help you keep your garden healthy and bountiful.