On Gardening: Summer’s garden assassins, hiding in plain sight
by Shane Harris
Special to The Star
Jun 09, 2013 | 6935 views |  0 comments | 75 75 recommendations | email to a friend | print
A brown marmorated stink bug is seen at a Penn State research station in Biglerville, Pa.  Photo: Matt Rourke/Associated Press file
A brown marmorated stink bug is seen at a Penn State research station in Biglerville, Pa. Photo: Matt Rourke/Associated Press file
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This summer as you work in your vegetable garden, you’ll notice insects are everywhere. Flying around, hiding under leaves, even feeding on your vegetables. Some insects you’ll recognize and see often, like aphids, caterpillars, butterflies, lady bug beetles and honeybees. Others are less visible and will likely go unnoticed unless you know what and where to look.

These unnoticed, yet interesting, creatures are what make the world of bugs so fascinating. Look for these “good” and “bad” bugs this summer in your vegetable garden.

Colorado Potato Beetles

In the adult and larval forms, these beetles are very serious pests of Irish potatoes and can also damage tomatoes, eggplants and peppers. The adult beetle is about 1 inch long, hard-shelled and yellow with 10 black stripes. Larvae are humpbacked, soft-bodied and brick red with rows of black spots along each side. Both adult and larvae are voracious foliage feeders.

Untreated infestations can result in complete defoliation. Hand picking will help protect plants if done often. Otherwise, apply Sevin when an infestation is first detected. Repeat applications may be necessary as eggs hatch. Dipel insecticides (Bacillus thuringiensis) are effective against larvae.

Spotted Cucumber Beetles

These beetles damage cucumbers, melons, squash and pumpkins. The larval stage feeds on the roots of corn as well as cucurbits. The adults are yellowish-green with 12 black spots on their backs. Larvae are small, white and soft-bodied. The beetles eat holes in the leaves and flowers. Young plants may be killed. Larval feeding on roots results in wilted, unproductive plants. These beetles also transmit bacterial wilt, a destructive disease of cucurbits.

This insect survives the winter as an adult in crop residue and weeds. Therefore, cleaning up weeds and garden debris in the fall will reduce the next year’s population. Cucumber beetles can be controlled by spraying a recommended insecticide when beetles are seen.

Mexican Bean Beetles

These are beetles whose adult and larval stages feed on the leaves of snap beans, pole beans, lima beans and, to a lesser extent, cowpeas. The adults are copper-colored with 16 black spots on their backs. Larvae are yellow and covered with spines (favoring a sunburst). The orange-yellow eggs are laid in clusters of 40 to 60 on the undersides of leaves.

These beetles feed on the lower surfaces of leaves, but high populations can be seen feeding on all above-ground portions of the plant. They leave leaf veins undamaged, giving the leaf a skeletonized appearance.

Mexican bean beetles are easily killed with most garden insecticides, but if left unchecked, they can completely defoliate bean plants. Sprays should be directed to the undersides of leaves.

Assassin Bugs

These predatory insects are of great benefit to gardeners. They are proficient at capturing and feeding on a wide variety of prey including other bugs, bees, flies and caterpillars. Prey is captured with a quick stab of the assassin bug’s long mouthparts. After being immobilized by a paralyzing toxin, the prey’s body fluids are then drawn through the bug’s straw-like mouthparts.

Most species of assassin bugs are gray to black or brownish in color, though some are brightly colored. Ambush bugs are a type of assassin bug that lie in wait for their prey on flowers. Some of these species are colored to blend in perfectly with their flower hiding places.

The wheel bug is the largest of the 150 or so species of assassin bugs known of in North America. Adult wheel bugs are gray and approximately 11⁄4 inch long. Its name comes from the distinctive, cog-like crest arising from the top of the thorax, or middle section, of the wheel bug’s body. Wheel bugs are voracious predators and will even attack large insects, such as tomato hornworms and grasshoppers. They will not bite humans readily, but when they do, the bite is very painful.

Stink Bugs

These bugs are about 5/8 inch long as adults and green or brown in color. They earn their name by giving off a foul odor when handled. The young resemble the adults in shape but are somewhat more rounded. Young stink bugs are often seen clustered around the group of eggs from which they hatched. Adults and young suck plant juices from plants.

Characteristics of damage vary with the type of vegetable. On lima beans, there is little evidence of feeding on the outside of the pods, but when the damaged beans are removed, they are shriveled and spotted with slick brown stains. Stink bugs feeding on young okra pods and corn ears cause these vegetables to be distorted or crescent-shaped. Tomatoes that have been fed upon show whitish-yellow spots.

Removal of weeds from within and around the garden may aid in reducing stink bug numbers. However, be prepared to apply a recommended insecticide when stink bugs are seen in the garden.

For help on other home and garden questions, contact your local county Extension Office or visit us online at www.aces.edu.

Shane Harris is an Extension Agent for the Alabama Cooperative Extension System.
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