Cotesia congregata and other Braconidae
Braconid wasps- Kind
- Wild — attract it
- Best for
- Microctonus vittatae kills adults; wild only, background
Pest
Flea beetles
Phyllotreta, Epitrix & other Alticinae
The short answer
Flea beetles are tiny leaf beetles, mostly 1/16–1/8 inch (1.5–3 mm) long, with enlarged hind legs that make them jump like fleas when disturbed. The adults chew small round holes and shallow pits in leaves, and the damage looks as if the leaf was hit with shot. Different species specialise: crucifer and striped flea beetles on cabbage, kale, radish and other brassicas, potato and eggplant flea beetles on potato, tomato, eggplant and pepper, and spinach flea beetles on spinach and beet. They are a seedling problem. Young plants can be stunted or killed, but once plants have about five leaves they tolerate several beetles each. Row cover from sowing, later planting and a trap crop of radish are the main garden tools.
hero macro · crucifer flea beetle on a shot-holed brassica seedling
A crucifer flea beetle (Phyllotreta cruciferae) on a shot-holed brassica seedling. Photo: pending.
Identification
Adults are tiny, oval, hard-shelled beetles, mostly 1/16 to 1/8 inch (1.5–3 mm) long. The spinach flea beetle is larger, up to about 1/4 inch, and the pale-striped flea beetle is about twice the size of the others. Colours vary by species: shiny black, bronze, bluish, brown or metallic grey, and some have white or yellow stripes. The sure sign is the thick hind legs, which launch the beetle like a flea when you touch the plant.
The damage is as distinctive as the beetle. Shallow pits and small, rounded, irregular holes, usually under 1/8 inch, are unique to flea beetles, according to University of Minnesota Extension. The larvae are slender, pale grubs 1/16–3/16 inch long. Most live in the soil and feed on roots; a few, such as the spinach flea beetle, feed on leaves. Larvae usually do little damage. The main exception is the potato flea beetle: on potatoes, flea beetle larvae can cut straight, narrow tunnels into the tubers.
Damage symptoms
Almost all the damage is done by adults feeding on leaves in spring. On a big plant, a scattering of shot-holes costs nothing. On seedlings and small transplants, heavy feeding can stunt, wilt or kill the plant. Damage is usually not serious beyond the early seedling stage. The exception is potato, where flea beetle larvae can tunnel into the tubers. University of Maryland also notes that some species can transmit viral or bacterial diseases.
- Small round holes, most under 1/8 inch (3 mm), scattered across the leaf like shot
- Shallow pits on the leaf surface that have not gone all the way through
- Seedlings and new transplants that stall, wilt or die in spring
- Tiny beetles that jump off the plant when it is touched
- On potatoes, narrow tunnels in the tubers from larvae
Lifecycle & degree days
Adults spend the winter in leaf litter, hedgerows, windbreaks, woods and under plant debris. They become active once it reaches about 50 °F (10 °C) in spring, which in Maryland is late April to early May, and feed on weeds and the earliest-planted crops. Females lay eggs in the soil or in plant tissue. The larvae feed on roots for up to a month and pupate in the soil. Most species have one or two generations a year, and some up to three, so a second wave can show up in summer.
- Generations / yr
- Usually 1–2; up to 3 for some species
- Active from
- About 50 °F (10 °C); late April–May in Maryland
- Egg hatch
- 7–14 days
- Pupal stage
- 11–13 days, in the soil
- Overwinters
- Adults, in litter, hedgerows and plant debris
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Host crops
Each species has its own range. The crucifer, striped and western black flea beetles (Phyllotreta) attack brassicas. The potato flea beetle (Epitrix cucumeris) attacks potato, tomato, eggplant and pepper, and the eggplant flea beetle (E. fuscula) attacks eggplant. The spinach flea beetle (Disonycha xanthomelas) attacks spinach, beet and chard. The pale-striped flea beetle (Systena blanda) feeds on beans, squash, corn, lettuce and many weeds. University of Maryland lists eggplant, corn and brassicas as the most susceptible, with some feeding on almost every vegetable.
Monitoring & action thresholds
Action threshold
More than 5 beetles per seedling
University of Minnesota's home-garden figure. For eggplant it gives thresholds by plant size: 2 beetles per plant under 3 inches, 4 at 3–6 inches and 8 above 6 inches. For commercial cole crops it gives treatment at 10–20% of the stand showing feeding damage. UC IPM adds that once cole crops have five leaves they tolerate several beetles per plant without damage. After the seedling stage, a garden rarely needs to do anything.
Check seedlings and new transplants every few days from the time they go in, looking for fresh shot-holes and beetles that jump when you brush the leaves. Yellow sticky traps set among the plants show when flea beetles are active. On a larger planting, they often arrive from the field edges, and only the outer rows may need attention.
Beneficial
Biological control
Natural enemies are not a dependable answer for seedlings in spring. The native braconid wasp Microctonus vittatae kills adult flea beetles, but University of Minnesota says it is not very common and is not sold; lacewing larvae have also been seen eating flea beetles. Wisconsin Horticulture reports some success with products containing insect-killing nematodes, but names no species, stage or trial, and we found no published trial of Steinernema carpocapsae against flea beetles. Most flea beetle larvae live in the soil, so soil-applied nematodes would mainly reach larvae, not the adults that do the leaf damage.
Cultural controls
Protect plants through the few weeks when they are small, and time planting so that stage misses the spring peak. Older plants outgrow the damage.
- Cover seedbeds and transplants with floating row cover from the start, so adults cannot feed or lay eggs. On eggplant, drape it over hoops rather than on the plants. Remove it before flowering on crops that need bees
- Plant as late as the season allows. Plants grow faster in warm weather and outpace the damage
- Sow a trap crop such as radish ahead of the main crop. For farm-scale cole crops, University of Minnesota gives 7–14 days earlier, on about 10% of the area
- Rotate to crops the local species do not feed on, and clear weeds and debris around the beds
- Lay reflective mulch straight after planting
Chemical, last resort
Treat only seedlings that are losing the race — older plants tolerate flea beetles, and sprays are wasted on them. Use only a product whose label lists your crop. Soap can scorch cabbage and Brussels sprouts. Pyrethrins and esfenvalerate are toxic to bees: never spray plants in flower. Pyrethrins are highly toxic to fish; keep drift and runoff out of waterCheck any product before it goes on. Open the compatibility matrix →
- Insecticidal soapREI 12 h
- PyrethrinsREI 12 h
- EsfenvalerateREI 12 h
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
University of Minnesota Extension, Flea Beetles (Schuh, Wold-Burkness, Hutchison, Hahn & Hines, 2022)
Wisconsin Horticulture, Flea Beetle (Lowenstein, Groves & Liesch, 2026)
University of Maryland Extension, Flea Beetles on Vegetables (updated 2023)
UC IPM Pest Notes, Flea Beetles (UC Statewide IPM Program)
UC IPM Pest Management Guidelines: Cole Crops — Flea Beetles (Natwick, Joseph & Dara, 2020)
UC IPM Pest Management Guidelines: Cucurbits — Squash Bug table (pyrethrin REI, 2016)
UC IPM, Relative Toxicities of Pesticides Used in Cucurbits to Natural Enemies (2016)
National Pesticide Information Center, Pyrethrins General Fact Sheet
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
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