Margaret Lauterbach: Japanese beetles, billbug weevils come calling for your lawns

Special to the Idaho StatesmanJune 6, 2014 

Our lawns might be under attack from two different groups of insects if some Japanese beetles have evaded all of the traps set up by the Idaho Department of Agriculture.

Surviving Japanese beetles will be emerging from pupas this month, and billbug weevils laid eggs last month and this. When billbug eggs hatch, the larvae will feed on grass roots, as the Japanese beetles did last summer and fall.

Japanese beetles are new to Idaho, having arrived in containers of nursery plants from other states within the past three years.

If you find a Japanese beetle, don't smash it beyond recognition, but deprive it of air and send it to the Idaho Dept. of Agriculture, 2230 Old Penitentiary Road, Boise, ID 83712, Attn: Dr. Paul Castrovillo. Tell what it was on when you caught it and in what part of the Treasure Valley you found it.

Here's what to look for:

• Fat oval beetle, less than a half-inch long.

• Dark metallic green in color, showing mostly around head because bronze wings obscure much of body, so it has a dark green head and upper back, and a bronze back.

• Tiny white tufts around the perimeter of the body.

Make sure it meets all three descriptions above. As of last year, they had been found from Pioneer Cemetery to the area around Plantation Country Club along State Street. Adults feed heavily on ornamental and edible foliage until they mate in late summer, and lay eggs. I've heard that after they appeared in the Salt Lake City area, it took seven years for the Utah Department of Agriculture to eliminate that invasion.

If you suspect one or the other culprit has eaten your lawn's roots, try pulling up a clump of brown grass. If it pulls up easily, no roots. Then you treat for billbugs if there are tiny white grubs in the lawn, and watch for Japanese beetle adults if there are not.

GLADIOLUS

Thinking of planting gladiolus bulbs? They grow and flower well here, if the bulbs are sufficiently large (at least one inch in diameter) to produce flowers. If you want them to produce next year, too, you'll have to either plant them quite deeply or else dig them at the end of summer.

The usual rule for depth of bulb or corm planting is to plant them twice the depth of the corm or bulb. Many gladiolus planters plant corms 4 inches deep. If you plant them at that depth, be aware they will not come back next year. The reason? Once they're planted, they begin building a new corm on top of the old one, from which the flower stalk grows.

That means the new corm will lie at a shallower depth - too shallow to produce a new corm that will grow, flower and support the tall plant. The new corm will also be vulnerable to frost damage.

Dedicated glad growers dig them after flowering, and about two weeks later, pop the two corms apart, keeping the top one and discarding the old one. They then dust the new corm with sulfur and store them in a cool but nonfreezing environment with good air circulation. Some store them in pantyhose, knotting between bulbs; others have frames with screens for storage.

FRUIT TRESS

If your fruit trees are overloaded with fruit, as my white peach tree is, don't be too hasty to thin fruit. "June drop," a phenomenon in which fruit trees drop a lot of fruit that has set, will do at least some of the thinning for you. It happens with stone fruits as well as with apples.

Send garden questions to melauter@earthlink.net or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.

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