A number of pests will attack vegetables before and after seedlings emerge. Damping off and seedling blights caused by various fungi can rot seeds before they are visible above ground.
Sow vegetable seeds at the recommended time when soils have warmed, and use seeds of high vigor. This allows seeds to germinate quickly before they fall prey to fungi.
Insects also will take advantage of slowly germinating seeds planted too early in cold soils, such as beans and corn sown in April. Seedcorn maggots commonly attack these seeds. In May, when warmer soils allow seeds to germinate quickly, damage is minimized.
Other common seedling pests include cutworms, flea beetles, slugs and, occasionally, millipedes. Remember that floating row covers aren’t meant to control these pests. Row covers may trap insects emerging from the soil under a protective cover with their favorite food.
Row covers can be effective in preventing damage from insects such as spinach leafminer and cabbage worm that overwinter outside the garden.
Animal pests of seedlings include birds and rabbits. After seeds emerge, both birds and rabbits will consume them. Birds will also eat seeds prior to their emergence. Rabbits wait until after seeds emerge. Barriers and repellents may be partially effective at minimizing damage.
In general, pest control for vegetable seedlings involves good cultural practices to prevent problems before they occur. Good practices include seeding at the proper time, keeping seedlings growing vigorously through adequate watering and thinning to prevent crowding.
For more information, see the following Colorado State University Extension fact sheet(s).