Do traps reduce Japanese beetle populations?

ASK THE HORT AGENT

Question Do traps reduce Japanese beetle populations?

Answer Not really. In North Carolina, Japanese beetles begin to emerge from the ground in June. However, peak emergence happens in July. Needless to say they are very hungry when they dig out. According to the University of Kentucky, Japanese beetles are the most devastating pest of urban landscape plants in the eastern US. While they will feed on over 275 different kinds of plants, some of their favorites include grapes, roses, crape myrtles, hibiscus (high biscuits for the folks in Johnston County) and maples.

Japanese beetles are the adults, and white grubs are the immature beetles. Most of their life is spent underground in the immature form. The adult beetles only live about 30 to 45 days after emergence. In addition to hungry, they are also feeling very sexy.

These beetles can fly long distances to find food and friends. Their ability to devastate plants is worsened by their instinct to hang out with other Japanese beetles. As beetles start to feed, other beetles are attracted to the food and fun. If you allow a few beetles to party on your plants for a couple days, the guest list will really expand.

Beetle traps capitalize on the party invitation process. Traps have two methods of “calling” beetles. First, they have a floral scent, which usually smells like concentrated roses. This covers the food aspect. They also have a pheromone scent, which smells like perfumed ladies to the male beetles. This covers the fun aspect. The two smells work together to advertise one heck of a party. Japanese beetles will come from miles around (down wind) to attend this shin ding.

Unfortunately, most folks hang the traps near the plants they are trying to protect. As beetles are migrating toward the trap, they land on these same plants. They usually decide to take a bite before they hit the road again. If the plants are on their “favorite” list, then they may take several bites. The next thing you know, several real Japanese beetle parties have broken out on your prize rose bushes. The beetles decide to stay at the rose bush party instead of going on to the trap party. After all, you can only have so much fun.

Beetle traps are good for calling them in, but they only catch a fraction of the beetles. While the traps will catch 75% of the beetles that approach them, they only drop the entire population about 30 to 40%.

One of the best things you can do is bust up the parties yourself. Take a cup and fill it half up with soapy water. Walk around early in the morning or late in the day and rake the partying beetles into the soapy water. If you can keep them from congregating, they will not cause as much damage. For other great control tips, visit http://www.ces.ncsu.edu/depts/ent/notes/O&T/flowers/note44/note44.html If you don’t have internet access, call me at 910-893-7533 or email me at gpierce@harnett.org

If you have already purchased a beetle trap, I would suggest you wrap it up and give it to one of your neighbors. They will be surprised by your generosity and most likely give you something in return. Hopefully, it won’t be a puppy from the dog they refuse to get spayed.

Gary L. Pierce

Horticulture Extension Agent

Harnett County