Hey, it's the Beetles!

Hey, it’s the Beetles!

Every year around the last week in June, Jefferson County can count on Japanese beetles to make an appearance in our yards. The adults emerge from the ground to begin feeding on plants, with about 300 species attractive to them. They will eat the leaves, flowers, and even fruit!  Activity is most intense over a 4 to 6 week period beginning in late June, after which the beetles gradually die off. Individual beetles can live about 30 to 45 days.

These guys usually feed in large groups and are most active on warm, sunny days.  They prefer plants in direct sunlight. These feeding clusters of beetles can really do some damage.

So, where did they come from?  

They were discovered in New Jersey in 1916 and yes, they were originally from Japan. Our mild weather, grassy lawns and lack of natural predators was perfect for their numbers to multiply.  They were first discovered in southern Louisville in 1937. Today they can be found in every one of Kentucky’s 120 counties.  Japanese beetles are considered the most devastating insect pest in our urban landscapes.   

Controlling the adults is just half the battle (see the link below for more info). The larvae of these beetles are the grubs that can do so much damage to our lawns and golf courses. They eat the roots of turf plants, causing them to brown and loosen like a piece of carpet (early fall). These lawns will probably not recover. Early detection is the key. The best time for a curative grub control is early to mid-August! With curative control, treatment is applied in late summer, after the eggs have hatched and grubs are present. Insecticides used for curative control have relatively short residual effectiveness (usually 2 to 3 weeks or less). Therefore, proper timing is important. The best time to apply curative grub insecticides in Kentucky is in early to mid-August when grubs are still small and their feeding damage is relatively light. Grubs are still vulnerable to treatment in late August and September but as they grow larger, they become progressively harder to control, and damage to the turf already may be severe. By late September, in response to cooler soil temperatures, some grubs already may be moving downward and out of the treatment zone. Remember to water-in the insecticide as soon as possible after the application.

Not every lawn will have a grub problem, but correct timing and control can help get a handle on these insects.


Grub Control:
http://www2.ca.uky.edu/entomology/entfacts/entfactpdf/ent10.pdf

Insecticides for Grub Control:
http://www2.ca.uky.edu/entomology/entfacts/entfactpdf/ef441.pdf

Japanese Beetle Control:

http://www2.ca.uky.edu/entomology/entfacts/entfactpdf/ef451.pdf