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10 Neat Things About Flea Beetles
by Dorothy Dobbie
by Dorothy Dobbie



The Local Gardener magazines, Ontario Gardener, Manitoba Gardener and Alberta Gardener, are published by Pegasus Publications Inc.

Drawing on her 30 years' experience as a senior executive in the magazine publishing industry, Dorothy launched Manitoba Gardener in 1998, initially running the business out of her home. Two years later, Dorothy's daughter Shauna, living in Ontario, jumped into the fray with Ontario Gardener. And two years after that, they started Alberta Gardener. Visit us at www.localgardener.net and register for our "Ten Neat things" newsletter. Watch Shaw TV for garden tips and Listen to CJOB for the Gardener Sundays at 9:08

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October 22, 2017

1. Who pepper sprayed my plant leaves? Flea beetle damage, in its early stages, looks like flecks of white or gray pepper on the leaves of plants. Later, these "flecks" become shot holes that make it look as though someone hit the plant with a fine shot gun. Heavily damaged leaves may become lacy.

2. Jump up, turn around.

Flea beetles are so named because they hop like fleas. The beetles have strong hind legs that help them spring up when disturbed.

3. A many splendored bug.

There are many types of flea beetles preying on specific plants but you can have several types preying on one plant. They are all small, one-sixteenth to one-eighth of an inch and have those tell-tale strong hind legs, but their coats can vary. The base colour is shining black, sometimes with an iridescence of green or purple, but they might be black with two shiny, wavy yellow stripes, or they might have many yellow stripes. There is one, the eight-spotted flea beetle, which has a red head and eight large white spots on a black field on its back.

4. Rain, rain go away.

Flea beetles enjoy warm, dry sunny days when they actively feed, and even fly if it's over 14 C. They don't like rain and will hide on the underside of leaves.

5. Gourmands.

Many flea beetles love cruciferous plants, including cabbages, mustards and the prairie-ubiquitous canola. In certain warm dry Julys, they will swarm into cities, blanketing and destroying urban gardens. Another group favour solanaceous plants, which include tomatoes, potatoes and peppers. Still other groups enjoy squash, beans, corn, sunflowers and lettuce.

6. Maggoty menace.

Flea beetles overwinter as adults in shrubby places, emerging to lay eggs in the soil at the base of plants when the temperatures exceed 10 to 14 C. At cooler temperatures, they will hop from plant to plant. As the weather warms, they will take to the air. The adults lay their eggs in the soil near vulnerable seedlings, and so the use of diatomaceous earth when planting may help deter infestations. Plants are most vulnerable at the cotyledon stage as the pale, cream-coloured larvae (one-eighth to one-third inch long) are voracious feeders on tender stems and leaves.

7. Ammunition for your arsenal of weapons.

In addition to diatomaceous earth, the vigilant veggie gardener can use floating row covers to protect their emerging crops. There are also beneficial nematodes, predatory braconid wasps and tachinid flies that will come to your defence, and kaolin clays that can be sprayed on older crops. Planting a trap crop of mustard or radish will lure the adults to their favoured food, assuming that is the variety you are trying to avoid. You can also interplant your veggie crop with thyme, catnip or mint to confuse them with the strong, masking scent of these plants. Dust tomatoes, potatoes and peppers with talcum powder to repel them. A concoction of two parts rubbing alcohol, five parts water and one tablespoon of liquid soap sprayed on foliage will also help.

8. The good with the bad and ugly.

Just as with everything else, some flea beetles are considered to be helpful in that they will attack noxious weeds such as leafy spurge. Aphthona nigriscutis has been used as a biological control of this imported weed, Euphorbia esula, which produces latex that is harmful to cattle.

9. What's been eating my potatoes?

The little black and sometimes black and bronze, potato flea beetle, family Chrysomelidae, will attack the leaves of your plant while the larvae can damage tubers. The best control is crop rotation. Do not confuse this with the dreaded Colorado potato beetle (Leptinotarsa decemlineata), the orange and black striped beetle with the spotted thorax.

10. Crop killer.

The most worrisome flea beetles, from an economic point of view, are the ones that attacks canola crops and cruciferous (brassica) vegetables (see "Gourmands" above). They can also be of concern to the local gardener who may, on certain calm, hot, summer days, be invaded by a swarm of these guys flying in off canola fields. The bad news: they can do a lot of damage in a short period. The good news: they don't often stay too long. Unfortunately, they also spread bacterial and viral diseases.

Dorothy Dobbie Copyright© Pegasus Publications Inc.

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