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10 Neat Things About Scale Insects & Mealy Bugs
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 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

April 6, 2014

1. Woolly or waxy.

Without getting into the Latin or Greek, which bores most of you, scale insects can hide in a waxy house while they suck the juices of your plants or they can be covered in a woolly looking substance, in which case, you have mealy bugs.

2. My houseplants have been invaded.

Scale insects can attack both garden and indoor plants and the hardest one to deal with is the insidious mealy bug. I have a friend who swears they breed in the carpets - they do not-but they can live for up to four months, incubating away and producing almost microscopic copies of themselves in a very inconspicuous way until their populations seem to explode overnight. Dealing with them takes diligence and vigilance, not to mention vigilantism!

3. Murder the mealies.

They are easy to kill. Really. But mealies are also very good at hiding. And they do not breed in soils, so it is the plant itself that you have to explore, becoming very intimate with its most secret crevices and crannies. Treat the infestation with neem oil or diluted alcohol or simple insecticidal soap and water, but treat them over and over again. And pay attention to those secret places. Scales need to be scraped from tender twiglets, that have perhaps been softened first with a bit of alcohol or soap. Outdoors, the sharp spray from a hose can boost them off your branches.

4. These bugs make me see red.

Okay, so we have to resort to the Latin terms sometimes. Both insects are members of the "superfamily" Coccoidea. This is only important because it leads to a connection to a close relative, the cochineal (Dactylopius coccus), the female of which has red guts especially after fertilization, and is (or was) used to make red (carmine) dye for use in food stuffs, lipsticks and so on. Some people are allergic to carmine dyes.

5. A bug, a bug, your kingdom for a bug!

Okay, so we are taking a little licence here with the words of the Bard, but in fact, when Montezuma was on the rampage in 15th century Mexico, the 11 cities he conquered were required to pay an annual tribute of 2,000 blankets and 40 bags of cochineal each! Cochineal became second only to silver as an important export for Mexico until the War of Independence in 1821, when it lost its monopoly. Later, the dye was synthesized. By the way, the bugs are raised on a diet of Opuntia, a species of cactus that grows wild in many parts of southern Canada, including Manitoba, Alberta and Ontario. The variety that hosts the carmine producing bug, Opuntia ficus indica, does not grow here.

6. They are la-zee!

In many species, the female adult scale insect loses her legs once she is firmly attached to a plant after breeding. She really doesn't need mobility anymore because now her only job is to feed and produce the next generation. She then loses her eggs and dies. The young are called crawlers, because the only time they have mobility is just before they mate. That's also the only time an insecticide in likely to be helpful in killing these insects, so why not skip the chemicals and scrape and squish? Dormant oil in early spring can keep infestations down. The eggs are laid in May and the crawlers are on the move in June.

7. Freedom a-day-and-a-half.

Depending on their species, some males get a day or two of unbridled freedom, growing wings to find a mate. They are yellow and microscopic and sadly the flying males never get a chance to feed. They die in a day or two. For her part the female scale just keeps right on sucking until she dies and the crawlers she has produced take over, literally eating her out of both house and home!

8. Short-tailed mealies and long-tailed mealies.

Short tailed mealy bugs are most likely to be the ones sucking the lives out of your house plants. They can be identified by their short filaments that are about one-quarter the length of their bodies. They lay eggs - 500 to 1000 of them - and they don't need the services of a male to do so. Long tailed mealies, on the other hand, have very long filaments that are as long as their bodies growing from their abdomens. They are about 3 mm long, oval in shape, yellowish-grey with a darker stripe down their backs. These gals need a male to reproduce and, most fascinating of all, they give birth to about 200 live nymphs. No eggs!

9. The curse of the honeydew.

Both mealy bugs and scales produce honeydew, as do aphids, which can attract black mould. Serious infestations outdoors on trees such as maples can cause honeydew splashes that may be quite a nuisance. In one instance, about 10 days after the leaves emerged on the trees, newly hatched scales eggs "filled the air with minute crawlers that looked like pollen dust" as they landed on everything.

10. Outdoor scales.

These tiny insects attack cedar spruce and pine needles, where the crawlers cover needles and look like paint splotches. They take up residence on the underside of leaves. While their sucking doesn't usually do the tree that much harm, a heavy infestation can attract a lot of black sooty mould which can suffocate a tender tree or shrub, depriving it of its ability to photosynthesize.

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