Walker: How to protect your leaves from harmful insects

Special to The Idaho StatesmanMarch 27, 2014 

I love watching the progress of leaves in the spring. First the leaf buds get bigger and bigger, then tiny, tender leaves appear. Before you know it, they'll be producing shade and cover for birds. They also provide food for insects.

Today I'll introduce you to two insects that use leaves for food and shelter. One insect is beneficial, the other is not.

Leafcutter bees (see accompanying photos) are beneficial insects that are excellent pollinators. They cut distinctive, neat round holes at the edges of leaves. When you see these holes, smile and be happy that you're hosting these important beneficials.

Leafcutter bees don't eat the leaves; they use them to line their nests. Rose and lilac leaves are a couple of their favorites, but they also love thicker leaves such as found on euonymus shrubs. These important bees only lay 35-40 eggs in their lifetime.

If the damage really bothers you or you're afraid they'll chomp on the rose leaves you plan to enter in the fair, cover the leaves with cheesecloth so that the leaves continue to get air circulation, but the bees can't reach them.

Our second insect of the day is the black vine weevil. These insects chomp away willy nilly on leaves (see accompanying photos). You're unlikely to see them because they do their dirty work while we sleep. The adults chomping on leaves is only superficial damage. The real damage is caused by their babies.

Black vine weevils lay their eggs underground among a plant's roots. When the babies hatch, they chow down on roots and cause severe damage to the plant - even killing plants.

One way to control black vine weevil is to stay up nights and pick the bugs off the underside of leaves. If that doesn't appeal to you, you can wrap the stems of affected leaves with corrugated cardboard, secure the cardboard in the middle with a twist tie and wait until they bed down for the day. Remove the cardboard and hopefully they've decided that the cardboard makes a great resting place.

Unfortunately, black vine weevils have mutated to resist pesticides. Any pesticides used are more likely to kill beneficial insects and beetles.

As soon as leaves appear in the spring, black vine weevils are close behind. When you notice damage, start taking steps to get rid of them. The larva in the soil can sometimes be killed with beneficial nematodes (available at some nurseries), but larva must be treated at a certain time of the year: May and/or late August.

Enjoy leaves this spring and hopefully you'll get damage that will make you smile, not the kind that makes you mad!

If you have any questions or suggestions for columns, contact Elaine Walker at highprairielandscapedesign@yahoo.com.

Idaho Statesman is pleased to provide this opportunity to share information, experiences and observations about what's in the news. Some of the comments may be reprinted elsewhere in the site or in the newspaper. We encourage lively, open debate on the issues of the day, and ask that you refrain from profanity, hate speech, personal comments and remarks that are off point. Thank you for taking the time to offer your thoughts.

Commenting FAQs | Terms of Service