Q. Are these nematodes on my tomato roots in the picture I sent to you? Picture sent from reader A. Yes, you have them. Once you have nematodes they are a permanent pest in your vegetable garden. Your future with them is in managing their new home but you will never be rid of them.             In the past, soil fumigants were available that would dramatically reduce their numbers and easily make them manageable. These soil fumigants are no longer available to homeowners and highly restricted even for commercial applicators due to their potential in damaging the environment. Root knot nematode on tomato             There are multiple approaches in managing nematodes. One way is to exclude them. You can do this by growing vegetables that are highly susceptible in pots or containers. If the pots or containers are in direct contact with the soil containing nematodes, the nematodes will move into the container eventually.             You can impede this by putting down a layer of coarse gravel on top of the soil and putting the containers on top of the gravel.             If you want to grow in the ground with nematodes then heavily enriching the soil with organic material such as high-quality compost will help to deter them. Keeping the soil as healthy as possible is a great deterrent. Nematodes do not seem to like heavily enriched soils.             Another deterrent is to select plants that nematodes do not seem to like very much. There are some vegetables somewhat resistant to nematodes but it is quite lengthy. I will post this list on my blog but a few of them include broccoli, cauliflower, chives, and many mustards.             There are other plants which nematodes really like a lot but plant breeding has produced some varieties which are resistant to nematodes and a few plant diseases. These varieties have capital letters such as V,F,T,N after their names which designate their resistance. The capital N in this case designates nematodes.             Another method is growing marigolds in the vegetable plot. The most effective way is to grow a solid stand of marigolds for at least 2 to 3 months in the planting bed. Turn these marigolds under the soil so that they decompose. Then plant your vegetables.             Some people grow them on the borders of the vegetable plot but it is not as effective as growing a solid stand and turning them under.             There are some products available such as Clandosan which gives some benefit and could also be incorporated into the soil.