Japanese Beetles

They’ve munched on a few of my Oak Leaf Hydrangeas, eaten up some Sunflower leaves, but so far, damage is minimal.  I checked the neighbour’s yard, which has more horticulture than mine, and they have only eaten a few scattered grape vine leaves.

Japanese Beetles have begun their annual breakfast and lunch, gobbling up plants of all kinds.  Roses are their favorite, along with Japanese Maples, Cannas, Zinnias, Raspberry and Clematis, but they will eat almost anything deciduous. 

Japanese Beetles are easy to spot.  Usually in clusters or families, they are about two or three times the size of a housefly.  Their heads are metallic green with copper coloured bodies.   

Damage is also easy to spot, with sections of the leaf missing.  They will usually start eating in one corner of the plant, then continue eating until satisfied.  Japanese Beetles will usually eat leaf flesh first, leaving veins and stems intact. 

Gardeners should take comfort in the fact that Japanese Beetles rarely do much damage beyond cosmetics.  Roots and stems remain healthy and will help the plant bounce back in spring unscathed.  Another consolation is that the adults, at beetle stage, will only eat until early August, at which time they will finish eating and laying eggs. 

The bad news is that the eggs will hatch, becoming small grubs, living a few inches below soil surface.  In winter they will dig deeper into the soil, only to emerge in spring to feed on the roots of grass.  The larvae grubs become pupae and quickly become adults, anxious to have dinner again.

Gardeners have a few options to reduce populations of Japanese Beetles.  In July and early August, when they are at their peak, Japanese Beetles can be hand-picked.  Go early in the morning when Beetles are dozy.   Bring a bucket of water with a little soap and simply grab the beetles and toss in the bucket.  Shaking the leaves over the bucket will cause them to fall and drown.  This control method seems unscientific but will easily conquer hundreds of beetles in a very short time. 

Nematodes are tiny organisms that feed on the larval stage of Japanese Beetles.  Apply on the lawn in fall or early spring when grubs are immature and populations will be greatly reduced.  Encourage your neighbour to do likewise, so both of you can enjoy green grass in spring, and a beetle-free garden in summer. 

Japanese Beetle traps work wonders to reduce adult populations.  Place the trap in the far corner of the yard, away from your valuable plants.  Empty the traps as often as necessary, perhaps more than once a day. 

Adult beetles can be sprayed with Bacillus thuringiensis, which will quickly knock them down.  Apply as beetles appear and reapply after a rain. 

Finally, do what you can to create a garden that is bird friendly.  Crows, Starlings, Bluejays, Cardinals and Robins love the larval stage of beetles and some will feast on adults.  Racoons and skunks, who might not be welcome in your backyard will dig up grubs in the lawn early in spring.