Rose Chafer Beetles

Rose chafer beetles

Early summer means it’s time for the rose chafer beetle invasion.  If you live on sandy soil your garden may be particularly hard hit.  The name rose chafer is misleading.  While they are very attracted to rose flowers, they’ll eat the leaves and flowers on many kinds of plants.

Rose Chafer,  Credit: DaBinsi, Flickr

Rose chafer beetles are tan, sometimes with a greenish cast, with reddish orange legs and short antennae.  They are about a 1/2 inch long when mature and are strong fliers.  In June they emerge from the soil where they have been pupating and begin feeding on everything in sight.  Plants are sometimes covered with the beetles.

Damage to plants is mainly cosmetic; the plants do recover when the beetles stop feeding and die, near the end of June.  But the loss of flowers and the sight of leaves with only the veins remaining make many gardeners ready to fight.  In June lots of chewed up leaves and flowers may mean a rose chafer invasion is taking place.

For those who grow grapes, rose chafers mean more than cosmetic damage.  Grapes are generally blooming at the time the rose chafer emerges and the hungry beetles love to eat grape flowers and buds, which means the loss of the grape crop.

The life cycle of the rose chafer begins when adult beetles lay eggs in sandy soil in June.  Tiny grubs soon hatch and burrow deeper into the soil.  Unlike the European chafer beetle grub the rose chafer grub does not damage turf grass roots.  It grows all summer, and then goes deep into the soil to rest for winter.  In the spring grubs move toward the surface, eat for a short time then turn into pupae for a couple of weeks, before emerging from the soil in June to start the cycle over.

Since female rose chafer beetles prefer to lay eggs in sandy soil, higher numbers of the beetles are found in gardens planted on sandy soil.  But the beetles can fly quite a distance to feed.

To control rose chafers gardeners can hand pick the beetles, dropping them into a container of soapy water.  Shaking a plant lightly will often dislodge dozens of the beetles.  On sturdy plants a hand vacuum can be used with the dirt cup full of beetles emptied into soapy water.  

Common garden insecticides such as sevin and malathion will kill the beetles.  But insecticides will need to be re-applied after each heavy rain and every 10-14 days.  Systemic insecticides, like those found in rose care products, will work but the beetle has to take a bite of the plant before it is poisoned, so some damage continues to occur. 

Whenever using a pesticide, read and follow the label directions for mixing and applying the product exactly.  Make sure the plants you want to protect and the insects you want to kill are listed on the label.  Different insects or different plants can have different application and mixing instructions.

Plants could be covered with row cover material while the beetles are heavy.  It must be securely anchored to the ground so beetles don’t crawl under it.  Grapes though, need to have visits from pollinators to make fruit so a row cover won’t work.  Pesticides may also kill some pollinators but are the best option for grapes if beetle numbers are high.

Credit Maine.gov

Some early studies by the USDA have found that spraying the kaolin clay based product called Surround® on grape vines helped repel rose chafer beetles.  That product could also be sprayed on trees and shrubs being eaten by rose chafers but be aware that it gives sprayed plants a whitewashed appearance.

There is a lure scent that has been developed for rose chafers that can be used in Japanese beetle traps.  If you use a product like this put it far away from the plants you want to protect.  Otherwise it will draw more rose chafers to the area which may feed on plants before entering the trap.

One thing you do not want to do is to encourage your chickens or other birds to eat the beetles.  Rose chafer beetles contain a toxin that can sicken or kill birds and small animals. That’s why they are so abundant and damaging; they are not eaten by other wild things.

The good news is that the invasion is short lived.  By the end of June in most areas the adult rose chafer beetles are gone, leaving behind eggs for next year’s beetle crop.