Quite often I get asked the question, I have grubs in my lawn, will Nematodes get rid of them?
Managing pests on home lawns is a different tactic than it was prior to the implementation of Ontario’s cosmetic pesticide ban in 2009.
Recently Dr. Michael Brownbridge of the Vineland Research and Innovation Centre made this comment, pests, disease and weed issues are far, far less if you’ve got a healthy lawn to start with. Lawns must be looked upon as systems, if pests come along, they need to be dealt with accordingly. Typically, white grubs and chinch bugs are the insect pests that demand the most attention.
In order to effectively control pests such as white grubs, it’s important to understand their biology. Here is the biology:
- The European chafer will lay its eggs in the soil in June and July
- Once the eggs hatch, the larvae will live in the soil and feed on organic matter, including plant roots and thatch
- Their movement in the soil is dependant upon soil moisture and food availability
- If not controlled, by the fall grubs will make their way deeper into the soil to overwinter
So how do Nematodes work? How can we use these naturally occurring organisms to our advantage? The key challenges include how to get the organisms to the pests, how they should be applied, what formulations are available and best timing.
Nematodes are soil dwelling organisms which once applied will seek out the host species (grubs). They enter the host/grub through the mouth carrying a bacteria that kills the grub. The bacteria multiplies and the Nematodes themselves survive by feeding on the bacteria.
However…According to Dr. Brownbridge, here is what must occur first in order for Nematodes to be somewhat effective…
- Nematodes must be applied in high enough numbers and close enough to the target insect
- Nematodes must be refrigerated and fresh. It it’s too hot, they will die.
- Optimal time to apply nematodes in Ontario is late August or September
- The life cycle of the Nematode must be conducive with the life cycle of the grub
- When applied, the lawn should be very moist/wet (How do we handle municipal watering bans?)
- Aim to apply on cool and cloudy days
- Do not mix the Nematodes with treated/city water, if chlorine is in the water – it will kill the Nematodes
- Ensure that your lawn is already healthy and fertile
As you can see, the window of opportunity is quite small. Various trials have been conducted at the Guelph Turfgrass Institute, and the results are inconclusive. The best control of grubs during trials occured when a combination of Nematods with a Bioinsecticide was used, but then only 30-60 per cent mortality was obtained.
When grubs are present in your lawn, other animals tend to be attracted to the grubs. We have all seen lawns where raccoons and skunks have damaged the lawn. (Stay tuned for more on that.)
So what next…more research is needed. New grass varieties are coming into the market what are better suited to the sustainable lawn. They have superior root systems, making them able to better use water and nutrients, and they are more drought tolerant.
