Questions We’re Often Asked: Something’s Bugging My Plants!

First you notice something is amiss with your indoor plants. The foliage is becoming mottled. Eventually it dies and falls to the floor. As you pick up the leaves, you notice a strange substance like soot there. The remaining leaves are sticky with glossy patches and again, perhaps spotted with black powder.

Closer examination will reveal sap sucking lice have taken up residence. The sticky, glossy patches are their excrement. The black powder is a strain of fungus that thrives on it. Any one of three pests may be responsible. Aphids cluster on the new shoots and in the leaf axils, eventually in large masses. They are soft-bodied varmints, often green or yellowish in colour, but may also be red or black. Worldwide, there are around a thousand species. Apart from causing direct damage they are also the principle vectors of plant viruses. Should you lightly shake the foliage and what appear to be small white moths fly out, you plants are under attack by whitefly and their larvae. Again these are both sapsuckers and, to a lesser degree, virus vectors.

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The last of this despicable trio is harder to detect. Scale insects do indeed look like tiny brown fish scales. Often preferring to locate on the stems or trunks of indoor plants, they, too, suck sap while depositing their excrement below. The soil-dwelling larvae of a fourth common pest may feast out of sight on the fine hairs located near the tips of roots. This interferes with the ability of the plant to absorb water and nutrients. These are fungus gnat protégé. The adults are often mistaken for fruit flies and, like them, are prone to kamikaze dives into glasses of wine. Aphids and whiteflies succumb to spraying with insecticidal soap, a widely available natural insecticide safe to use indoors. Three or four applications, five days apart, may be necessary to eliminate all the pests as they emerge from the eggs that shelter them from the spray. Scale insects are more difficult to eradicate, since their protective covering or ‘scale’ is impenetrable to home pesticides. An effective, if time-consuming answer is use a Q-tip to dab each scale with rubbing alcohol. Fungus gnat larvae hidden in the potting soil are also difficult to eradicate. But the adults are highly vulnerable to a simple commercial trap called most descriptively ‘Sticky Stiks.’ These yellow adhesive strips are mounted on a plastic prong that is pushed into the soil. The colour attracts the emerging adults, which become ensnared once they land on the sticky surface. Sold in most garden centres and hardware stores, each one is effective for about six months. ‘Sticky Stiks’ are also an excellent defence against aphids and white flies.