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Battling the Evil Flea Beetle

Of Mice and Mountain MenThe adult flea beetle is a tiny (1/10 inch long) black, brown or bronze beetle that can jump like a flea when you disturb it. You’ll know it’s around when you see the small, round “pinholes” they chew through leaves. They will attack most vegetables, flowers and weeds but are particularly fond of brassicas (cabbage family), potatoes, spinach, radishes and eggplant.


Flea Beetle Life Cycle

Flea beetles are found throughout North America. The larvae live in the soil and are thin, white, legless grubs with brown heads that feed on plant roots. Adult Flea Beetles emerge from the soil in spring to feed and lay eggs on the roots of plants. The adults die out by early July. Their eggs hatch in about a week. The larvae feed for 2 to 3 weeks then pupate in the soil. The next generation of adults emerges in 2 to 3 weeks. These voracious pests produce two to four generations per year before the final generation of adults settles down for overwintering.

These beetles are most damaging in early spring when an infestation can kill seedlings. As plants mature they are better able to survive and outgrow the damage, unless the beetles carried a plant virus.

Battling the Enemy

Prevention is often the best defense. The larvae overwinter in soil and can be destroyed with regular hoeing and cultivating. Be sure to remove all debris from previous crops and keep the area weed free. Weeds are an important early season food for flea beetle larvae. Without cover and food, the larva will starve.

While your plants are young and most susceptible, use row covers, hoop houses or cloches to keep the little buggers at bay until the first generation of beetles has passed and your seedlings are large enough to withstand an attack. Cultivate the soil around plants before and after planting to destroy any flea beetle eggs and larvae in the soil.

Flea beetles like to hide in cool, weedy areas. Prevent them from hopping onto your susceptible plants by surrounding the crops with a 3- to 4-foot-wide strip of frequently weeded bare ground or closely cropped grass. A heavy layer of mulch atop the garden soil can interfere with the adult beetle’s emergence from the soil and return to lay eggs.

Hand to Hand Combat

Don’t bother trying to hand pick these pests: they are so small and so quick that you’ll never catch them. They can be vacuumed from leaves or washed away with a hose, but they’ll be right back.

Smoke and Mirrors

You can try to confuse the beetles by interspersing crops they like with some they don’t, or with flowers and herbs like Queen Anne's lace, dill, and parsley, which attract beneficial bugs to eat the beetles.

"Trap crops" can help. Plant a favored, sacrificial crop like radishes (which sprout quickly and are inexpensive) to attract flea beetles away from the main crop. The trap crop may then be harvested (if it survived the attack) or destroyed after the main crop has established itself sufficiently to fend off flea beetle injury.

Bring Out the Artillery

Garden insecticides containing carbaryl (Sevin), spinosad, bifenthrin and permethrin provide good control for about a week. However, because the plants produce continuous new growth and the highly mobile beetles will rapidly reinvade, these measures must be reapplied often. As with all pesticides, carefully read and follow label directions. Pay particular attention that any flea beetle insecticides being considered are properly registered for use on that crop.

DE and Tools

For those of us who prefer non-chemical weapons, Diatomaceous earthis one of the more effective all-natural repellents. Be sure you get the food grade, not the stuff made for use in swimming pool filters. It is applied as a dry powder to the plants and the very small, sharp particles repel the beetles by cutting them so they dehydrate. D.E. will need to be reapplied after a heavy rain, and you’ll want to rub some on the under sides of leaves too.

D.E. is not a poison, so it cannot be absorbed through the leaves and transferred to the plant’s fruit. Rain and watering will wash it off the leaves and into the soil below. This is OK because it helps control the adult flea beetle as it lays eggs on the plant roots, but The WormExpert says DE will not harm your earthworm population.

Horticultural oils and some Neem oil insecticides also have some repellent effect on this insect.

D.E. Caveats

Be sure you wear a good dust mask any time you use D.E. because it is just as irritating to your nasal linings as it is to the bugs. Resist poking at or rubbing your eyes (or other sensitive parts of your body) while working with DE, and wash your hands thoroughly when you’re done.

It is also an indiscriminate killer. Keep it out of flowers where your pollinators will hang-out and don’t use it casually as it will take out many beneficial bugs as well as the flea beetles. It’s best to resort to DE when the Beneficials aren’t up to the job, and then only to get an infestation under control.

Know Your Enemy

The table below was compiled by the Colorado State University** and it lists which species of beetle favors what crops. If you know a particular denomination of flea beetle is prevalent in your area, you can tell what plants will have the most trouble from flea beetles and take the appropriate steps.

Table 1: Some common flea beetles found in Colorado.

Common name

Scientific names

Host plants, comments

Cabbage flea beetle

P. cruciferae

Wide host range, primarily of cabbage family plants (Cruciferae family). The most damaging species in the state. Two and occasionally three generations are typical.

Palestriped flea beetle

Systena blanda

Has the widest host range of all flea beetles including squash, beans, corn, sunflowers, lettuce, potatoes and many weeds.

Potato flea beetles

Epitrix cucumeris, E. subcrinita, E. parvula

Tomato, potato and other nightshade family plants.

Tobacco flea beetle

Epitrix hirtipennis

Eggplant and some other nightshade family plants. Most common in warmer areas of the state.

Tuber flea beetle

Epitrix tuberis

Potatoes. Larvae are associated with tuber injuries.

Horseradish flea beetles

Phyllotreta armoraciae, P. albionica

Horseradish, occasionally other mustards.

*Apple flea beetle

Haltica foliaceae

Larvae feed on evening primrose (Oenothera); Grape, epilobium, crabapple, zauschneria and other plants are occasionally damaged by the adults.

*Sumac flea beetle

Blepharida rhois

Currants, sumac, skunkbrush.

* Willow flea beetles

Disonycha spp.


* Species that have larvae that feed on leaves, similar to other leaf beetles

** W.S. Cranshaw, Colorado State University Extension entomologist and professor. 1/99. Revised 11/06.