Monday, May 7, 2012

June beetles cut new pecan shoots

    It almost looks like a ten-foot-tall deer has browsed out the tops of a young pecan tree (photo at right).  You can look over the entire tree and not find a trace of the offending creature that clipped off this spring's new growth. You can, however, find clipped-off leaves scattered under the tree.
   This kind of damage is caused by what is commonly known as June beetles.  There are numerous species of June beetles found in Kansas but the one that I've recently noticed crashing into my kitchen window after dark is the European chafer, Rhizotrogus majalis.
    The European chafer is a major pest of cool season grasses. This insect's C-shaped larvae (photo at left) live in the soil feeding on grass roots.  In late spring, larvae pupate and adult beetles emerge from the soil swarming to small trees or shrubs in search of a mate.
    Adults emerge after dark during warm (above 65 degrees) clear nights. It is during this adult swarm that the adult insect feeds on tender shoots, clipping off the foliage of young pecan trees. Adults are active only at night, hiding in the turf's thatch during daylight hours. The adult phase of the European chafer (photo above) lasts only one to two weeks before mated females burrow into the soil to lay eggs. There is only one generation of European chafers per year.

     Damage caused by the European chafer (photo at right) can slow down the growth of young trees but they usually recover when new buds break and form new leaves.  Control of this insect would require an insecticide treatment of the orchard floor in August to kill larvae in the soil. However, the cost of insecticide treatment is hard to justify considering that most damaged trees have yet to reach the age of commercial nut production.