Flea beetles are tiny, hopping, flea-like beetles of the genus Phyllotreta. To deal with flea beetles, it’s best to understand their life cycle. Adults emerge from the soil in spring and feed, laying eggs on plants’ roots. They die off by early July, but the eggs hatch in one week, with larvae feeding for two to three weeks. At this point, they fall off the plants, back into the soil to pupate, emerging as new adults in another two to three weeks. We might see as many as four or more generations per year. They thrive in full sun, particularly in drought conditions. That’s when they really come on in infestations. There are a couple of strategies for dealing with them… Delay planting to avoid the first peak population.
Cover seedlings with row cover until the adults die off. Provide shade for the crops that seem most susceptible to them. Apply a garlic spray to repel them from susceptible plants. (Simply run some garlic in water in the blender, let it sit overnight, strain it, and spray it). You can try to apply parasitic nematodes, but you have to get the timing right, as they only go after the larva. So as soon as you see the adult population collapse, apply nematodes. And keep the soil around the plants well watered, which will help kill off some of the larvae. Finally, try spreading petroleum jelly on pieces of cardboard and place these around your plants. These will trap any adults that land on them.