Japanese Beetle

 Japanese beetles were first discovered in New Jersey in 1916.  Now that they have made their way to Wisconsin, they are unfortunately here to stay.  No product will completely rid your garden of Japanese Beetles, the best that can be expected is to keep them within tolerable levels.  References to pesticide products are for our customer’s convenience and are not an endorsement or criticism of one product over another.  You are responsible for using all pesticides according to label directions.  Johannsen’s does not guarantee the effectiveness of any product.

 Understanding the life cycle of the Japanese Beetle is the key to control.  In the larvae or grub stage, Japanese Beetles do significant damage to the roots of ornamental plants, especially lawns.  As adults, they feed on the foliage or flowers of more than 300 species of plants.

 Spring:   When soil temperatures reach 50ºF the grubs that spent the winter deep in the soil of our turf grass begin to make their way up into the root-zone and resume feeding for about 3-5 weeks, (although they cause the most damage when they feed in August.) Thereafter, the grubs stop feeding and eventually pupate into adult beetles.

·         Apply Bayer Season-Long grub control liquid drench (Merit or Imidacloprid) to your lawn in May. This is a season-long grub control product, which is most effective when applied to your lawn in early May, however it can be used anytime through late summer.  This product is very effective when used as a preventative, because it kills the grubs as they are hatching.  It is not very effective on large mature grubs, so once you spot damage to your lawn, it is better to use Sevin or Dylox.

 Late June- Early August:   Adult beetles begin to emerge from the ground and begin feeding on the leaves and flowers of our ornamental plants.  The following controls may be used anytime adult beetles are present.

·         Physical removal by hand

·         Japanese beetle traps.  This is a good organic alternative, however, if one is going to spray with chemicals anyway, do not use the traps as they have been known to attract more beetles to your area.

·         Chemical sprays.  Several insecticides are labeled for use against adult Japanese beetles. Spray the plants that are being fed upon.  Read and follow all directions. Products with long residuals are more effective, however, Pyrethrins, Sevin and Eight, are slightly less toxic and may be used on edible food crops.

o       Pyrethrins Very short residual, effective only if the product actually hits the insect

o       Sevin (Carbaryl) Labeled for use on listed food crops and ornamentals

o       Eight (Permethrin) Labeled for use on listed food crops and ornamentals

o       Malathion Labeled for use on listed food crops and ornamentals

o       Isotox Use on ornamentals only.  Systemic action, long residual.

o       Orthene Use on ornamentals only.  Systemic action, long residual.

o       Bayer Advanced rose and flower insect killer (Cyfluthrin with Imidacloprid) Use on ornamentals only.  Systemic action, long residual.

 Late July, early August:   Adult female beetles lay their eggs 2-4 inches deep into the soil.  Both the male and female adult beetles die by late summer. Stop spraying for the adult beetles when they are no longer present.  Eggs hatch into grubs in about 2 weeks and begin feeding on the roots of turf grass.

 Mid to Late August (optimum time) into early September:  Treat the lawn with curative products to control the newly hatched grubs.  The feeding grubs will cause large dead spots in the lawn that resemble drought damage.  These dead areas can actually be “rolled” up, because the grass no longer has roots.

·         Sevin sprayed on the lawn  Quick kill, short residual.

·         Bayer Lawn Grub Control Granules  (Trichlorfon or Dylox) Granules*  Quick kill, short residual.

·         Bayer Season-Long grub control Drench* (Merit or Imidacloprid)   This product is best used in the spring, because by the time you spot damage to your lawn in late summer, the grubs are too mature for this product to be effective.  When applied in the spring it has a long residual and will still be effective on grubs as they hatch in August.

 Late September:  When ground temperatures begin to cool to about 60ºF, (usually after the first frosts of fall,) the grubs begin to move deeper into the soil to spend the winter.  Controls are no longer effective.

 Biological Controls

·         Milky Spore applied to the turf has been known to control grubs with varying degrees of success.  Milky spore has been known to last ten years with one application.  May be applied at any time of the year the lawn is not frozen.

·         Nematodes.  Johannsen’s does not carry nematodes at this time due to the difficulty in storage and proper application. 

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