There are two types of cucumber beetles that can plague Northwest gardens: striped and spotted. If unfamiliar with them, you may at first think you’ve encountered an unusual lady beetle, but that is not so. The spotted cucumber beetle is slightly larger than a lady beetle and is yellow with black spots. Their populations can be alarmingly large, and their damage can go undetected long enough to weaken young plants to the point of no return before the gardener is aware what it going on.

The striped cucumber beetle is slightly larger and more rectangular of body than the spotted, somewhat iridescent, and (obviously) striped. These fellows are newer to the gardening scene. I hadn’t encountered them until they devoured my young melon plants last year. The maddening creatures fall to the soil and are hard to find when disturbed. But let’s back up a bit.

Ohio State Extension has an excellent fact sheet describing the striped cucumber beetle: http://ohioline.osu.edu/hyg-fact/2000/2139.html. According the fact sheet these

“beetles often fly from their hibernating sites early in the season, even before plants emerge. As soon as the cucumber, squash, pumpkin, melons and related seedlings push up through the soil, beetles can eat off the stems and cotyledons, frequently killing them. Adults later feed on the leaves, vines and fruits of plants that survive. Sometimes, deep pits are gnawed into the rind, making the produce unfit for consumption or market.

Damage is also caused by the larvae feeding on the roots of host plants, which weakens the plant and makes it susceptible to other problems. Adults feed on beans, peas, corn and blossoms of other plants.

Most important, these beetles are vectors of a serious cucurbit disease known as bacterial wilt. Plants infected with the disease wilt quickly with leaves drying out prior to plant death. The causative bacteria, Erwinia tracheiphilia (E.F. Smith), overwinters in the bodies of hibernating beetles. These beetles introduce the bacteria into the plants through the fecal contamination of feeding wounds.”

As horrifying as this sounds, the fact sheet goes on to describe additional damage. Spotted cucumber beetles work similarly.

Another site (www.ghorganics.com/CucumberBeetles.htm) has a long list of suggestions for control of cucumber beetles. Control techniques vary from encouraging natural predators (tachnid flies, soldier beetles, parasitic nematodes, braconid wasps, lacewings and ladybeetles) to repellent plants and trap crops (broccoli, calendula, catnip, goldenrod, nasturtiums, radish, rue and tansy are repellent/ the more common marigolds may actually attract them and be used as a trap crop), chemical control (neem oil and pyrethrum) to confusion (foil below the plants), and more.

Early in the 20th century an English farmer of renown (Sir Albert Howard) considered pests to be an indicator of an unbalanced system, not enemies, but red flags to the observant that something is wrong with the farmer’s technique. Farming and gardening is a humbling endeavor, and it isn’t easy, with all the effort and thought involved, to embrace the idea that maybe it’s you that’s lacking.

Consider adding compost to your garden on a regular basis. Beneficial nematodes (one of the predators listed) need organic matter and the environment created by it to live and thrive. Grow non-edible plants that provide nectar and pollen for insect predators. These plants include daisies, chrysanthemums, carrot flowers (such as Queen Anne's lace), goldenrod, dill flower, clover, fennel, and pungent types of marigold. Create a complex growing environment that includes water, nesting habitat, and food for birds, insects, and reptiles such as snakes and lizards. Add a third dimension to your garden: height. This provides cover for many organisms and perches for birds. Be an observant gardener who uses the information being provided. You may lose this year’s crop, but be able to add components to next year’s garden that allow you to grow more of the food you desire.

Here are just a couple of websites describing a few natural predators of cucumber beetles.

www.organicgardeninfo.com/braconid-wasp.html (braconid wasp)
www.cirrusimage.com/beetles_soldier.htm (soldier fly)
www.oisat.org/control_methods/natural_enemies/parasitoids/ta... (tachinid fly)