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Researchers in Germany discovered that flea beetles’ ability to jump distances of hundreds of times their body height, at up to speeds of 11.8 miles per SECOND, lie in the enlarged femur of their hindlegs. Seriously. There are people studying this. Do you know how big flea beetles are? 1/16 to 1/8 of an inch long. That’s how big. Can you imagine being the scientist studying their jumps?! While fascinating, this little tidbit is not as important as the immediate question at hand- “how do we identify and control flea beetles in our gardens?” For that answer- read on. I just happen to like random nuggets of information and wanted to share one with you.
Flea Beetle is a general name referring to small jumping beetles of the leaf beetle family and some of the more common garden types include the crucifer, striped, western black and potato flea beetles. For our purposes, identification, damage and controls are very similar for all types. All adult flea beetles cause damage by feeding on the foliage and stems of susceptible plants, leaving small irregular pits and holes, giving a ‘shot hole’ appearance. Feeding can delay the establishment of seedlings and even kill plants. The small white larvae feed on roots of seedlings, and heavy infestation can cause seedling death. Flea beetles tend to be common on cruciferous crops, eggplant, peppers, tomatoes, potatoes, spinach, beans and melons.
Distinctive 'shot hole' damage
As I mentioned, adult flea beetles are very small and range in color from black, bronze, bluish-grey to brown. They are easily distinguished by the fact that they jump (like fleas) when disturbed. It may be very difficult (unless you are looking very closely) to actually catch them in the act; however, the damage they inflict on crops is usually quite obvious. Flea beetles are typically one of the very first garden pests active in my garden in Zone 6. They begin feeding as soon as temperatures reach the 50s.
Now- the important stuff… how do you control flea beetle damage on your veggies?
Row covers can be an effective physical barrier to stop beetles from reaching crops, as long as crops are being rotated (adults can overwinter in the soil). Covers must be securely in place as soon as plants emerge or are transplanted. If there are any rips, holes or openings in the covers, beetles are small and determined and will most likely find their way in.
Another option for forming a barrier is using a kaolin clay product which deters the beetles from feeding on sprayed crops. Thorough and consistent coverage is key here—if it rains, you’re going to have to coat the plants again.
Diatomaceous Earth (the ground-up fossilized remains of diatoms) is another option for physically deterring flea beetles. DE works in several ways. Pests don’t like the feel of the DE as they crawl through it and will avoid traveling over areas sprinkled with it. DE also causes dehydration and death by absorbing oils from insects’ exoskeletons- this dehydrating action is enhanced by the fact that DE’s rough scratchy edges can cut through insects’ protective exoskeleton. If pests ingest the DE it can absorb internal fluids, also leading to dehydration and death. DE remains effective as long as it is dry- so again, if it rains, you must reapply.
Trap crops are another way to go. Trap crops work by utilizing a crop highly favored by the beetles, such as Southern Giant Mustard, to lure the beetles away from the crop you want to harvest. The trick is to have the trap crop out BEFORE you plant your main crop (about 2 weeks beforehand) and planted close enough to the main crop to be an effective lure (within 8-12 feet). You can also utilize companion plants/intercropping to confuse or deter flea beetles. I’ve read that flea beetles will avoid the scent of marigold, peppermint, spearmint, tansy, wormwood, catnip and basil- but have no first-hand experience with this.
Encourage the presence of the flea beetle’s natural predator- Microctonus vittatae , a native braconid wasp, which kills and sterilizes adult beetles. The nematode Steinernema carpocapsae can also be used to inoculate larva, leading to a reduction in adult populations.
There are several organic insecticidal options available for controlling flea beetle. Look for products containing pyrethrins (derived from chrysanthemum), spinosad (made from soil bacterium), or azadirachtin (extracted from neem seed).
Do you battle flea beetles in your own garden? What tactics have worked for you?