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Garden: Killing destructive pests, but not pollinators

Nancy Szerlag
Special to The Detroit News

Because of the mild winter and early spring weather, this may be a big year for pests in the garden and I’m already on watch for invasions.

With all the buzz over pollinators and the alarming reduction of bee and butterfly populations, many of us realize using chemicals in the garden can have a disastrous effect on these beneficial bugs.

Spider mites, aphids, white flies and other tiny pests are easily dislodged from plants by a stiff stream of water. When hosing down a tree or plant be sure to hit the undersides of the leaves where pests are most often found. You will need to repeat the attack every few days as a new hatch occurs, but after a couple of weeks you will succeed in gaining the upper hand.

One key to success in winning the war against destructive pests is identifying the enemy to find out its life cycle and how and when to best to control it. However, many of the bugs you find in the landscape and garden are good bugs that attack the bad guys, while others are valuable pollinators, and learning to tell the difference is also key.

A great resource and field guide to sorting out and identifying who’s who in the garden is “Good Bug, Bad Bug” by Jessica Walliser (St. Lynn’s Press). Walliser also includes some preventative actions and recommends organic product controls.

The following website from the University of Minnesota lists many of the ready to use insecticides available to consumers and rates their toxicity to bees. Perusing this list will enlighten you to the fact that many pesticides listed as organic for use in the garden are also toxic to bees if used at the wrong time:

Organic oils such as canola, cottonseed and neem are rated nontoxic to bees on a residual basis but are toxic to them on contact. That means if you spray bees with any of these horticulture oils you will kill them. But once it’s on the plant it will not harm them.

So the safest time to spray any pesticides or herbicides, whether organic or chemical, is in the cool of the evening or very early morning when bees have left the garden and returned to their nests or hives.

Also, spraying plants when they are in bloom is a no-no. And spraying pollinator plants with horticulture oils may smother the eggs of butterflies and other beneficials so think twice before using any insecticides.

Nancy Szerlag is a master gardener and a Metro Detroit freelance writer. Her column appears Fridays in Homestyle. To ask her a question go to and click on Ask Nancy. You can also read her previous columns at