To control flea beetles in the garden, remove weeds from the garden, and plow or till the soil at the end of each growing season. Place row covers over plants until they are well-established, and sow plants later in the season to encourage fast plant growth. Apply a recommended insecticide, such as pyrethrum, if the beetles are damaging plant foliage, and place yellow sticky traps in the garden to capture mature flea beetles.
When using sticky traps to capture adult beetles, place the traps 15 to 30 feet apart between rows, and monitor the traps. If the infestation is severe, spot treat the plants with an insecticide that is recommended for flea beetles, or spread diatomaceous earth in the garden.
Beneficial nematodes are also used to control flea beetle populations. Apply the nematodes to the soil according to the instructions on the product packaging. Another option is to plant a trap crop, such as radishes, to prevent damage to other crops.
Plant the trap crop early in the season, and apply pesticide to the crops, or harvest the crops, before planting the main garden. Plants that are well-established can typically withstand mild pest damage, and insecticides or other preventive measures aren't necessary.