By Jim McCausland, Sunset senior garden writer

The Butchart Gardens near Victoria, British Columbia, is more than just a feast for the eye: it also would be a feast for insects, mites, and diseases if The Gardens’ staff stopped paying attention. They use Integrated Pest Management (IPM) techniques to keep pests at bay and minimize unintended environmental impact. This approach—which combines biological, mechanical, and targeted chemical controls with good growing practices—works well in home gardens too. I know because I use it.

Here’s how the people at The Butchart Gardens deal with trouble. In the list that follows, many native beneficial insects are included: their numbers are supplemented with identical, insectiary-raised critters as needed.

Diseases: Spray in winter and early spring with lime-sulfur. For fungus problems during the growing season, they apply Bacillus subtilis, which eats the bad fungus. For mildew on azaleas, they spray plants during the season with compost tea; so far, it has worked well with azaleas, but the same treatment has been ineffective on roses.

General insect problems: Spray susceptible plants in winter and early spring with dormant oil, which kills egg masses and overwintering adult insects. Spray plants that are susceptible to chewing and sucking insects with Neem oil before releasing beneficial insects; to eat or suck the leaves, harmful insects ingest the toxic oil on the leaves, but insects that don't feast on leaves are unharmed. Butchart gardeners also periodically release pathogenic nematodes that kill soil-dwelling larvae of insects such as cutworms, weevils, and crane flies.

Aphids: Controlled with lady bugs, with a tiny black-and-white bug called Orius insidiosus, with brown lacewings, and with a small native fly called Aphidoletes aphidimyza. 

Leaf-eating caterpillars: Controlled with Bacillus thuringiensis; they use BtK.

Spider mites: Controlled with predatory mites such as the native Amblyseius fallacis.

Thrips: Controlled with Orius insidiosus, and predatory mites such as Amblyseius cucumeris and the native Hypoaspis miles.

Weeds are controlled the old fashioned way: by lots of hand work.

To read an earlier blog on The Butchart Gardens, click here.