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Plant Protection - Japanese Beetles

The Japanese Beetle is one of the most dreaded of the lawn and garden pests.  Each year this shiny green and copper colored beetle inflicts millions of dollars of damage to over 275 kinds of shrubs, trees, turf, garden and field crops.  June and July are Japanese Beetle months in Georgia.

During most of the year (August through May), the beetle spends its life as a grub in the soil and feeds on grass roots.  When the weather becomes warm and moist, the grubs mature and emerge as adult beetles by the thousands.

Since the beetle has become so widespread, control measures such as State and Federal quarantines have become inadequate or ineffective.  Homeowners may protect their fruits and vegetables with insecticides such as liquid Sevin (carbaryl).  While Sevin is relatively safe, repeated use can result in a build-up of mites on plants.  Sevin is also toxic to bees, which pollinate crops, so do not use the dust form on flowering crops visited by bees.  Read and follow all label directions when using any pesticide.

Hand-picking is also effective if only a limited number of beetles are present.  To protect roses, tie the buds loosely in an old nylon stocking.  Certain traps are also available and can be used effectively if placed away from the plants to be protected.

If Japanese beetles are in your garden now, your lawn may be one of the sources of your problem.  In addition to feeding on trees and shrubs, beetle grubs feed on grass roots, reducing the turf's ability to withstand Georgia's summer heat and drought.  Lawns should be checked in September or October for the presence of beetle grubs (immature beetles).  To sample for Japanese beetles, select a square-foot area of the lawn.  Cut three sides of the square and try to roll back the turf like a carpet.   If you find more than ten fat, white, C-shaped beetle grubs per square foot, you should consider treating your lawn area.  Lawns may be treated with granular insecticide such as diazinon, isofenphos (Oftanol) or bendiocarb (Turcan).  Irrigation may be required after treatment.

Homeowners may also treat their lawns with Milky Spore.  Milky Spore is a soil-borne bacteria.  The grubs will ingest the bacterial spores, the spores will multiply within the insect, ultimately killing it.  The additional spores are then released back into the soil.  Milky Spore disease lasts for years and will not harm mammals.

READ AND FOLLOW ALL LABEL DIRECTIONS AS IMPROPER USE OF INSECTICIDES MAY AFFECT ANIMAL AND HUMAN HEALTH.