Archive for Sunday, June 13, 2004

Adult beetles known to strip leaves from trees

June 13, 2004


Douglas County residents should not hold their breath while waiting for "The Year of the Cicada," being touted in the news and on TV talk shows.

However, we are in the midst of a feeding frenzy of another visitor seen every three years. Most gardeners are familiar with grub damage in the lawn. If you have plants missing leaves, or seem to be overrun by June bugs at night, you are not alone.

June bugs or May beetles belong to the genus Phyllophaga. It is a large genus that contains some forty species. Adults vary in color from light brown to nearly black. Individual species are difficult to identify without examining microscopic characteristics. The adult beetles hide during the day by burrowing into the soil or sod. They emerge from the ground and fly to trees to feed shortly after dusk.

They continue to feed all night and return to the soil after daybreak. This can result in a tree being stripped of its leaves relatively quickly -- in some cases overnight. Though damage may look severe, healthy trees will produce a new set of leaves and be fine in just a few weeks.

The June bug life cycle takes three years to complete. After feeding and mating all night, females will deposit eggs in grassy areas during the day. Eggs will hatch into tiny grubs in about three to four weeks. The tiny C-shaped grubs will vary from white to off-white in color. They have a brown head, six legs and a dark area on the rear end of their body. They will feed for the remainder of the growing season on grass roots below the soil surface. In the fall, they will burrow below the frost line for overwintering. Next spring, the grubs will tunnel up to the root zone and resume feeding. Then the grass will be the most severely damaged. Next fall, the grubs will once again burrow down below the frost line for overwintering. The process will repeat in 2006 except that the feeding will stop by mid-June. At that time, a pupal cell will form and the grub will pupate into an adult. Adult beetles will emerge from the cases in July and August, but will not appear above ground until April or May of 2007.

Adult June bugs will only be active for a few more weeks. During this time they will be eating, mating and laying eggs. Though June bugs are not the most common species that produce white grubs, it is one that can cause significant damage to turf, trees and shrubs. Killing the adults is not practical as new populations will fly in each night. To control future populations, begin applying grub killers now. Lawns most likely to be damaged are those with streetlights or other lights that attract the beetles and those with moist soil.

Without sufficient rain to keep all lawns moist, the female beetles will prefer irrigated areas where it is easier to dig and lay eggs. However, with the recent rains, almost any turf area is a potential host site. Now is the time to apply the chemical Imidacloprid, found in the product Merit. This is a systemic insecticide that kills the grubs as they feed on the roots of the plants. It will take several weeks for the chemical to activate. During this time, the eggs will begin hatching and tiny grubs will begin feeding.

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