Tiny terrors show their true mite; BUG WATCH.
Red spider mite: One of the most common greenhouse pests, this minute creature feeds under the leaves causing flecking of the leaf surface, followed by the production of webbing and gradually the browning and death of the leaves.
The Solution: A tiny red predatory mite which rushes around the plant tapping the leaf surface as it seeks out its prey.
This mite, Phytoseiulus persimilis, will eat all stages of the red spider mite and even its eggs.
Put the predators in sheltered spots scattered around the plant.
Glasshouse whitefly: This pest looks like a minute moth and feeds by sucking plant sap, so reducing vigour and causing distortion.
Often occurs in huge clouds as whitefly breed very rapidly and reach epidemic proportions.
As they feed they excrete honeydew, which makes sticky patches on the leaves, pots, and adjacent plants or furniture.
The honeydew is soon colonised by black moulds which cause a soot-like layer to develop.
The solution: A tiny chalcid wasp called Encarsia formosa which lays a single egg in each scale.
This causes the yellowish white scale to turn black and kills off the developing whitefly. When the Encarsia egg hatches, the minute wasp cuts a hole in the scale and flies out.
Each female can lay up to 100 eggs. The end result is lots of black scales out of which new parasitic wasps hatch and hardly any young whitefly.
When you buy the wasps you receive many blackened scales (out of which the wasps hatch) and some adult wasps.
The integrated control company, Defenders, is now also marketing a tiny brown beetle called Delphastus which provides a very efficient means of dealing with serious outbreaks of whitefly.
Mealybugs: Especially common on houseplants, and a real pest in conservatories and on cacti, mealybugs huddle together in out-of-the-way places such as behind leaves and leaf joints.
They look like miniature woodlice but are greyish white in colour and covered with masses of waxy white threads, making them look like cotton wool. They feed by sucking sap, and so weaken and sometimes kill plants.
The solution: A close relative of the ladybird called Cryptolaemus montrouzieri. Both the adult (a black and brownish red ladybird) and its young (which look like a huge version of the mealybugs), are voracious feeders and eat numerous mealybugs in a day.
Greenfly and Blackfly: These pests suck sap and cause yellowing, weakening and distortion. They often spread lethal virus infections too.
The solution: A parasite and a predator are available to control the pests.
The parasite is another minute wasp which lays eggs in the prey. This time the aphid is killed and shortly afterwards the tiny new wasp emerges from the mummified, parasitised aphid.
The predator is a tiny midge called Aphidoletes aphidomyza. Its larvae are an orangey pink colour and about 3mm in length. They latch onto the aphid's leg joint and suck out its body contents, leaving behind an empty aphid skin.
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|Publication:||The Mirror (London, England)|
|Date:||May 20, 1997|
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