This pest hits home for us here at Gateway farm. We have battled with a deadly combination of flea beetles and excessive heat the past two seasons. We've won some, lost others but overall learned a lot. Most of our crops have come out on top, while other crops specifically in the brassicas family have struggled. We have since limited the varieties of kale, cabbage, and radish grown and found ourselves gravitating towards more crops in the gourd, daisy, and allium families.
THE FLEA BEETLE How to Identify: Most adult flea beetles are very small (1/16 –1/8th inch long). Flea beetles have large back legs which they use for jumping, especially when disturbed. Flea beetles can be black, bronze, bluish or brown to metallic gray. Some varieties even have stripes.
Affected Plants: Most species of flea beetle attack only one plant group or closely related groups. Common agricultural and garden hosts include members of the brassica (mustard, broccoli, kale, cabbage, collards, etc.) and solanaceous (potatoes, tomatoes, eggplant, peppers, etc.) families.
Visual Affect on Plants: Adult flea beetles cause the most damage by feeding on the leaves and stems. They create shallow pits and small rounded, irregular holes in the leaves. This type of damage is unique to flea beetles. Plants started from seeds are less tolerant of feeding damage compared to transplants, but both can be severely injured if flea beetle numbers are high.
Possible Prevention Solutions: 1) Floating row covers are extremely effective when placed on seedlings and left in place until plants are old enough to tolerate beetle damage. 2) Beneficial nematodes applied to the soil will destroy the larval stage, reducing root feeding and helping to prevent the next generation of adults from emerging. 3) 70% Neem oil is approved for organic use and can be sprayed on vegetables, fruit trees, and flowers to kill eggs, larvae, and adult insects. Mix 1 oz/ gallon of water and spray all leaf surfaces (including the undersides of leaves) until completely wet. 4) Plant a highly-favored crop, such as radish, as a trap crop, before you plant your main crop. 5) Adults overwinter under soil clods and plant debris; therefore, good sanitation practices are important to reduce overwintering flea beetle populations. Remove or destroy refuge sites by plowing or removing crop residues and weeds in the fall.