Illegal Pesticide Use – Neem Oil – Ontario Hort Soceity – Credit Valley Horticultural Society

Another Example of Illegal Pesticide Use since the Ontario Pesticide Ban

by Judy Zinni

As toxic chemical pesticides are now banned in our area, there are several lines of defense against

the lily beetle:

1) Hand-picking. Adult beetles can be picked from the plants and squished under your shoe, or thrown

into a bucket of soap and water (careful, they like to drop from the leaf and land upside down on the dark

soil, making it very difficult to find them again with their black underbody). Eggs and larvae are easily squished

with your gloved hand.


2) Neem oil. Whole Neem oil, with the active ingredient azadirachtin (look for this on the label), should be

applied to the soil around the plants as the stems start to emerge in spring, which will kill the beetles emerging

from their dormant winter seasonin the soil. Neem oil may also be applied on the plants later in the season

directly on the larvae; this apparently disrupts their ability to molt and thus breaks their life cycle. Neem oil left

on the leaves simply acts as a deterrent to the adult beetles which they find unpalatable.

Some Neem proponents suggest mixing Neem in a higher concentration than suggested on the packaging;

2-3 times stronger than noted, and suggest using warm water. Any application should be repeated every 7-10

days using a freshly mixed batch (mixed batches lose effectiveness in 8 hours), and should be applied in the

evening to avoid any potential issues with beneficial insects.


3) Some lily growers claim that coffee grounds around the plants, spread early in the spring, reduces the

emerging beetles. I can’t personally attest to this method, but the additional organic matter couldn’t hurt.


4) Looking to the future, there has been much research done with a specific parasitic wasp to control the

beetle. Last gardening season some of these wasps were released in the Ottawa area as a research project.

If all goes well, these wasps may becoming to our area soon. For more information on lilies, the web-site of

the North American Lily Society is helpful ( Locally, the Ontario Regional Lily Society holds

several meetings a year, has a bulb sale in October, and a show in July (web-site, I hope you

will enjoy the lilies in your garden.


Last Updated: 2011-11-21