JAPANESE BEETLES
Japanese Beetles are out this year in large numbers. They emerge from the ground in mid-June with an appetite for leaves and flowers of many of your favorite plants. A little background on the Japanese Beetles will go a long way in assisting you in controlling the most damaging of the white grubs found in North Carolina.
- Japanese Beetle life cycle
- Control Methods for Adult Beetles
- Control Methods for Grubs
- Pesticide Safety precautions
Japanese
Beetle Life Cycle
The Japanese beetle, a member of the scarab beetle family, was first reported in North America in 1916. The 1/2 inch long metalic green adults have bronze-green streaks on their wing covers. Adults emerge as early as mid May, but more commonly during a 4 to 6 week period from early June through mid July. Highest populations occur the first 2 weeks in July.
Japanese Beetles are very damaging in several ways. They feed on over 275 different kinds of shade and fruit trees, shrubs, flowers, small fruits, garden crops, and weeds throughou the summer. Japanese beetle adults eat flowers and chaff foliage, leaving only a lacy network of leaf veins. They also mate soon after emerging and deposit 40 - 60 eggs in small batches 2 - 3 inches deep, especially in damp soil of lawns, golf courses and pastures.
The spherical eggs double in size within a few days and hatch in mid- to late-July. The grub stage beetles are a serious pest of the roots of grasses and shrubs. Many eggs and young larvae perish in extremely dry weather. The newly emerged cream colored larvae (grubs) with brown heads begin to burrow through the soil and feed on roots until cool weather of late October forces them into hibernation. Damage to root systems will occur for the most part during the fall/early winter period and then again in the early spring. Areas of dead grass appear if large numbers of grubs are present, especially during dry spells in September and early October.
As the temperature warms in March, the white grubs return to the root area at almost ground level and begin feeding again. At this time they are much larger and more difficult to control. They complete feeding, then pupate (sleep and develop into an adult). The cycle begins all over again next June. One generation develops each year. back to the list
Control Methods for Adult Beetles
Management of Japanese beetles is at times difficult and other times relatively easy. Correct timing and economical control measures are very important. If you want to control the adult Japanese beetle, the time to do this is when they are actively feeding on leaves, such as roses and crape myrtles. There are several different insecticides that can be applied to the plant leaf surface to assist in controlling the adult Japanese beetle, Select only one product to apply at a given time. Sevin 50WP or Orthene are recommended for homeowner use on trees and shrubs. The foliage of ornamental plants can be protected by dusting or spraying with one of the following pesticides:
- Sevin 50W
- Diazinon 25EC
- Pyrellin EC
The best time to control the grub stage of the Japanese beetle is
when the grub is actively feeding near the soil
surface. This type of feeding occurs in April through early May
and from August through October. I suggest making the
pesticide application during the August and early September. The
reason is the earlier the control of the grubs, the less damage
they will do to the rootsystems of grass and shrubs. Also, it
takes less insecticide to control them when they are small as
opposed to the spring time when the grub has reached a full size.
Plant roots can be protected from the grubs by applying one of
following:
Pesticide
List
Insecticides other than Sevin will kill grubs more effectively if they are watered in after application; Sevin should not be watered in.
Milky Spore
One product in a little bit of a different category is Milky Spore. Milky Spore is a naturally occurring bacteria that is effective in controlling Japanese beetle grubs only. This product is best applied on an overcast day in late September or early October to a soil that has a pH level between 6 and 7. The results are not as fast as the chemical insecticides, but the effects last many years. Once established the milky spore will naturally spread to untreated areas. As a last point, studies have indicated that traps for Japanese beetle adults have no real impact or the populations in the area and may draw in others from as much as a 1/4 mile away. back to the list
ALWAYS READ ALL LABEL DIRECTIONS BEFORE APPLYING ANY PESTICIDES. The plants that the pesticide is labeled for will be listed on the label. Always think safety first and follow all recommendations. Recommendations for the use of agricultural chemicals are included in this article as a convenience to the reader. The use of brand names and any mention of commercial products does not imply endorsement nor discrimination against similar products not mentioned. back to the list
Mark Blevins , Horticulture Agent
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