nematodes and overseeding


Hello, I live in Toronto and we have some grub damage on our front and back lawns. It is Sept 23, ’23. Can we apply nematodes and then overseed right away or do we need to wait to overseed. We heard it is better to overseed in the fall. Temperatures look very good for these two tasks for the next two weeks at least. The Ontario website says to wait until spring to seed but that doesn’t match many of the other gardening websites I have checked out. We are thinking of repeating the same steps in the spring. Thoughts on all of this? Thanking you in advance


Thank you for ontacting the Toronto Master Gardeners regarding overseeding your lawn and nematode application.

In general, the best time to seed a lawn is the late summer or early autumn. The optimal temperatures for planting grass will depend on the specific species you choose, but many grasses germinate best when the air temperature is between about 15C and 24C.  So our current weather is ideal for overseeding.

Once seed is applied, lightly rake to cover the seed with a thin layer of soil, but don’t over do it.  You want to lightly cover the seed with soil/compost to help with germination and protect from birds, but you don’t want to bury it too deeply. You will need to keep the soil moist at all times. The tender grass shoots will quickly dry out and die if not kept moist.

Ideally, you would want to apply the nematodes after your yard is prepared for the lawn. There are three species of beneficial nematodes which are used for the biological control of soil pest insects. While lethal to several different types of soil-dwelling insects, beneficial nematodes are completely harmless to plants, animals and humans, and are an effective and safe alternative to chemical pesticides.

 Nematodes can be applied anytime but should typically be timed with the lifecycle of the target pest and soil temperatures.  Optimal soil temperatures vary for each species of beneficial nematode, but generally fall within about 20C to 28C, so application is typically done in the spring and autumn.

Nematodes have a limited “shelf life” in their transportation containers. Most suppliers recommend that the nematodes be applied within two weeks of receipt.  Before application, nematodes should be stored a fridge. Most suppliers recommend two applications about 7 to 10 days apart. Check with your suppliers’ specific recommendations for storage, viability and application.

Hope this helps