When Devra Boesch nears a peach tree in her yard, she notices some unusual sounds.
‘‘When I walk under the tree, I hear crunching and humming,” said Boesch, a master gardener in Middletown.
The sounds are coming not from the tree itself but from the legions of Japanese beetles covering it.
Boesch’s tree is not alone when it comes to the infestation of the metallic green and coppercolored bugs. The population of Japanese beetles in the area this summer is extremely high, experts say.
One theory for their high number is the use of Milky Spore. Years ago, a product using this naturally occurring bacteria was used to help prevent Japanese beetle infestation. Milky Spore was commercialized about ¹0 to ¹5 years ago in this area, said Nancy Adamson, a Maryland Cooperative Extension home horticulture expert.
But the Milky Spore product has a life expectancy and its ability to work fades over the years, Boesch said.
It needs to be replenished about every ¹0 years, Adamson added. So people might need to reapply it now.
The weather conditions last summer also explain the large number of Japanese beetles.
For white grubs, the larvae of Japanese beetles, to survive, moisture is necessary in the ground around the time the eggs are laid, explained Stanton Gill, the regional extension specialist in nursery and greenhouse management in central Maryland.
‘‘Last year there were record amounts of rain during the egglaying period,” Gill said. The increased moisture helped a large number of grubs live.
Additionally, increased development in the Frederick area has augmented the number of beetles. Farm fields are being turned into lawns, giving the grubs places to mature, Gill said. Also, the grubs gain food sources from the landscaping added to the new communities.
‘‘Older communities, in general, have less [beetles],” said Steve Dubik, the Maryland Cooperative Extension horticulture consultant for Montgomery County.
Natural defenses against the beetles grow over time. Areas develop predators that consume the beetle larvae, and the soil builds up defenses. The new turf in the developments does not have these defenses and thus has a higher beetle population.
While buried underground, where they develop throughout the year, the larvae cause damage by ingesting the roots of plants and grass.
The adult beetles feed off the foliage of hundreds of plant species and fruits and consume en masse. The beetles come out at once, but some ‘‘act like scouts,” Adamson said.
Once a beetle finds a good food source, it sends out a pheromone, or chemical, to others to bring them to the area. The beetles devour the food source until it is completely ‘‘skeletonized.”
When trying to control beetles, it is more effective to try ‘‘to control the larvae in the lawn,” as opposed to the adult beetles, Gill said.
Milky Spore is one natural defense useful in controlling grubs, Dubik said. The product destroys the grubs while they mature.
The beetles will be laying their eggs for the next few weeks, so treatments should be effective until midSeptember.
Japanese beetle traps are generally used to control the adult beetle population. The traps are designed to attract beetles. If placed properly, away from plants where they will become sidetracked, and emptied regularly, explained Gill, the traps can be useful. But the traps do attract beetles other than those already in a yard.
Otherwise, beetles on easily accessible plants can be handpicked.
‘‘Just knock them into a jar or can halffilled with soapy water,” Boesch directed.
Overall, these four experts agree that controlling Japanese beetles in their white grub stage is the best method of treatment. They also agree that with the recent wet weather, residents in the area should expect large numbers of the beetles again next summer.
Originally published at The Gazette. Thursday, August 4, 2005