Invasion of the Japanese beetles

They’re coming, they’re coming!
By Mary Conroy
Invasion of the Japanese beetles

Adult Japanese beetles sometimes emerge as early as mid-May in eastern North Carolina. Peak emergence occurs mid-late June in most areas and lasts a few weeks. How we hate to see these green beetles arrive in our gardens and devour any tender green thing in sight. Rose buds and crepe myrtle seem to be two favorites here in the Carolinas.

These dreaded insects actually begin as grubs. Females tunnel 2 to 5 inches into the soil and deposit eggs. Adult beetles look for green lawns with good soil moisture for egg laying. In 3 to 4 weeks, small grubs (larvae) hatch from eggs and develop through three stages (instars), with the first two stages lasting about 3 weeks. The last larval stage remains in the soil from the fall through spring. In spring and early summer, white grubs pupate 3 to 6 inches deep in the soil. Adults emerge from pupae in about 3 weeks.

Moles, raccoons and skunks love to feast on grubs, so if you see them in your garden or lawn it may indicate a grub population below the grass surface. You will mostly find the grub in areas that receive sun (they like the warmth) and water. Grubs also eat the roots of the grass, so watch for lawns that show wilting and browning of irregular shaped areas.

What to do? Insecticides such as imidacloprid (Merit) or halofenozide (GrubEx) can be applied prior to seeing damage, such as in late July to lawns likely to show damage. All of these insecticides should be watered into the soil for best results. Lawns should also be watered prior to application. The advice to put out the Pheromon trap bags is not sound. These attract the insect, so if you use them place them as far away from your prized plants as possible. Milky spore (Bacillus popilliae) is an organic way to control grubs. Allow this process to completely saturate a treated area, about 2 to 4 years.

Look for milky spore treatment at www.planetnatural.com. You can see a video on You Tube.

About the Author

Mary Conroy is a Master Gardener in Forsyth County. Visit her online gardening forum: www.gardeningcarolina.com

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