Vegetable Program
Insect Management

Flea Beetle, Crucifer

The crucifer flea beetle is uniformly black and shiny, about 2 mm in length, while the striped flea beetle has two yellow stripes on its back. These flea beetles only feed on Brassica crops; those found on corn or solanaceous crops are different species. Adults spend the winter outside the field, in shrubby or woody borders, and move into fields in May. Adults feed on leaves and stems, leaving small round holes. Eggs are laid in soil near the plant. Larvae feed on root hairs and pupate underground. New adults emerge in late July or early August and feed throughout August. Spring crops are damaged by over-wintered adults, while fall crops are damaged by summer adults. Feeding declines in September.

Heavy feeding can kill seedlings, and moderate damage can delay maturity, reduce yield, or make crops unmarketable. Crops with more waxy leaves (cabbage, broccoli,kale) are less attractive and feeding is more restricted to leaf margins, especially as crop matures. Crops with glossy leaves (bok choy, Nappa cabbage, mustard) are highly attractive, the whole leaf is damaged and the crop is susceptible until harvest.

Rotate spring crops as far as possible from last season's fall Brassica crops. Separate early and late-season Brassica crops. Avoiding early Brassicas (until July) breaks the repro-
ductive cycle, though it is not feasible for many growers. Incorporate and till crops immediately after harvest to kill larvae feeding on roots. Provide adequate water and nutrients for crop growth; avoid soil compaction.

Spun-bonded row covers provide excellent protection of the crop if well secured with soil or bags around all edges immediately after seeding or transplanting. Remove and replace the same day for cultivation, as needed.

Because Brassica crops differ greatly in susceptibility and attractiveness there is no fixed economic threshold that applies to all crops. Beetles can be difficult to count, as they hop when disturbed. Yellow sticky cards placed in the canopy or feeding damage can be used to determine beetle populations. Control if damage to cotyledons or seedlings is stunting growth, or if damage to greens will reduce marketability.

For Current information on production methods (including varieties, spacing, seeding, and fertility), weed, disease, and insect management, please visit the New England Vegetable Management Guide website.

Below you will find additional information on managing this insect, including photos, fact sheets, articles, and power point presentations, when available.

Fact Sheets Available on Flea Beetles:

• Management of flea beetle in Brassicas 2005
• PPT on Organic Flea Beetle Management in Brassicas and Eggplant
• PPT on Flea Beetle Integrated Pest Management (in Brassicas)

Articles Available on Flea Beetles:

• Flea Beetles: Plant Late Brassicas Far from Spring Crops

  

Photo by Ruth Hazzard, University of MA

Severe feeding damage by crucifer flea beetle in Brassica rapa.