Flea beetles are a problem for emerging canola crops in some areas of Manitoba this year. Spraying for flea beetle control can prevent further damage but the plant will already be weakened from the insect eating the above ground growth.
You can help your crop rebound from this damage by adding 1 litre of C3 and 1/3 litre of SuperB to the insecticide spray solution. The C3 boosts the metabolism of the damaged canola seedlings to get them growing, while the Boron in SuperB acts as a healer/sealer for the chewed plant.
Reducing the flee beetle impact on established seedlings will put you further ahead than starting over with new (expensive) canola seed or switching to another crop because of the lateness of reseeding.