Archive for Thursday, August 3, 2006

The green thumb

August 3, 2006

Grasshoppers, drought, leaf spots -- does the list of garden pests ever stop? Not yet!

As if these were not enough, now we can add one more assailant: blister beetles. Many gardeners are waking to find tomato plants stripped of foliage seemingly overnight. A closer inspection reveals masses of ash-gray bugs congregating on single plants, eating nonstop. Think twice before you reach out and grab one. Here is what you need to know about the dangers of blister beetles in your garden or flower bed:

Blister beetles get their name because their bodies contain cantharidin, a chemical that causes blisters on both internal and external body tissues. This caustic substance can injure gardeners and children at play. It can even be fatal for horses that eat hay containing blister beetle body parts. There are close to 60 species in Kansas, but just two blister beetles -- the striped and the gray -- cause most of the problems.

The beetles have a long, narrow cylinder-shaped body. Their heads are unusually large and are attached to a disproportionately long neck. They vary in color and size but can reach up to 1-and-a-half inches long. Blister beetles begin their life cycle as eggs deposited on the ground, under stones or on host plants by the adult female all summer long. Eggs hatch and larvae begin feeding on grasshopper eggs among other things. When winter arrives, immature grubs will pass the time in a pseudopupa stage -- protected from the elements. Next spring, they will go through a final molt and will resume feeding for a short period. The larva will enter the true pupal stage late next spring and mature adults will emerge midsummer to start the process over again.

Adult beetles can cause major feeding damage on the foliage of beans, peas and potatoes. But they also can attack field crops such as alfalfa and soybean putting livestock at risk.

A do-nothing approach may be the best method of control. Because they are highly mobile and travel in large numbers, "here today, gone tomorrow" can be used to describe their behavior. If you chose to spray, garden insecticides such as malathion, carbaryl (Sevin), methoxychlor, cyfluthrin, deltamethrin and pyrethrins are labeled for treating them. As always, read and follow all label directions. Finally, you can try hand picking, but remember to wear protective gloves to guard yourself against the caustic blister forming chemical found inside.


  • Bruce Chladny lives in Eudora. He is the horticulture agent at K-State Research and Extension-Douglas County.

For more information, call him from 8 a.m. to 5 p.m. weekdays at 843-7058.

Commenting has been disabled for this item.