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Flea Beetle

Ravageurs et maladies
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Flea Beetle.
Photo: Jardin botanique de Montréal (Steeve Schawann - MAPAQ)

Onglets

Description

Summary

Flea beetles are small shiny-shelled beetles. As soon as they sense danger, they jump and disappear. There are various species that attack some ornamental and food plants. The damage is caused primarily by adults, which chew many holes in the plants' leaves. Flea beetles thrive in warm, dry climates.

Signs and symptoms

  • Damage appears in early spring, with the return of warm weather.
  • The adults chew numerous tiny, circular holes in newly opened leaves.
  • The holes get larger as the leaves continue to grow.
  • In serious infestations, flea beetles can completely destroy terminal shoots. They are also capable of transmitting diseases.
  • Badly infested plants show a loss of vigour, along with delayed and uneven development.

Latin name (genus)

Altica, Epitrix, Phyllotreta, Systena, etc.

Host plants

Some ornamental plants, including dogwood, forsythia, hop, hydrangea, ninebark, potentilla, rose, Virginia creeper, viburnum and weigela.

Various food plants, including beet, broccoli, cabbage, corn, cucumber, eggplant, grape, potato, radish, rutabaga, spinach, sweet pepper, tomato and turnip.

Development cycle

Description and life cycle

Flea beetles are small jumping insects that belong to the order Coleoptera. They undergo complete metamorphosis (holometabolic insects). They pass through the egg, larva and pupa stage before reaching adulthood.

Eggs: Translucent, yellowish and elongated.

Larvae: Elongated, with bristle-like hairs; colour varies depending on the species.

Pupae: Resemble adults, but smaller.

Adults: About 2 to 5 mm long. The shell is shiny brown, black or metallic blue, depending on the species. They have well-developed hind legs for jumping.

Flea beetles overwinter as adults, buried in the soil or hidden under plant litter.

They emerge in early spring (May), at the first signs of warmth. They feed on weeds until the leaves on their favourite plants open, which they then feed on hungrily.

Shortly after emerging, flea beetles mate and the females lay their eggs on leaves, stems or in the soil, depending on the species.

The eggs hatch in about ten days. The larvae feed for about two weeks, but do not usually cause any serious damage. They then pupate, with the adults emerging about 10 days later. Depending on the species, there may be 1 to 3 generations each year.

Prevention and control

Favourable conditions

Early springs followed by warm, dry summers tend to produce large flea beetle populations. Dead leaves and plant litter left on the ground provide the insects with attractive winter shelter.

Identification

As soon as buds open in spring, regularly inspect young plants of susceptible species.

Prevention

  • Rotate vegetable crops.
  • Plant mint, thyme or white clover at the base of susceptible plants to mask their odour and discourage flea beetles from laying their eggs on them.
  • Keep plants vigorous by fertilizing adequately, pruning properly and watering during dry spells.
  • Avoid heavy feeding with high-nitrogen fertilizers and drastic pruning, which promote the growth of vulnerable, tender tissues.
  • Weed regularly.

Physical control

  • In spring, cover young plants with a floating row cover (white material that allows light and water to penetrate) before flea beetles appear.
  • During the growing season, shake plants over a container filled with soapy water, so that the adults will fall into it; pick off insects with a small vacuum.
  • In fall, rake up and dispose of plant litter from around infested or susceptible plants.

Biological control

  • Encourage the presence of insect-eating birds in your garden (sparrows and chickadees) and toads, avid predators.
  • Add soil nematodes to attack and kill newly hatched larvae.

Chemical control

The Montréal Botanical Garden does not recommend the use of pesticides to control flea beetles.

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