Nematode and weevils
I just read an article on your site that said to apply Nematodes upon the first rains in the fall. Yet Nematodes only seem to be available to purchase in the spring. I have potted plants that have and are being killed from root loss from winter through spring. It seems that this natural method to get rid of weevils will always keep me a step behind having to lose my plants then treat soil. Ideas? I am in Victoria, BC and am totally frustrated but in Canada this seems to be the only route for weevil control as there are no allowable pesticides that I can purchase. I need help now. Short of bagging up entire 20gallon pots and starting over.
Outside United States nematodes
First, identify what is causing the root loss. Fungal disease can rot the roots. Some insects can feed on the roots, but you can find the insects if you dig through the soil.
What plant is in the pot? You state there are weevils. What type of weevils?
Treatment will be determined by identification of the cause.
Nematodes, if needed can be applied as long as the soil has warmed. There must be a population of host larval insects for the parasitic nematodes to survive.