Advanced gardening New series on advanced gardening techniques with Steve and Val Bradley
You can listen to Steve on alternate Sundays 10am-2pm on BBC Radio Kent’s Sunday Gardening (BBC Local)
The predatory mite Phytoseiulus persimilis can eat up to five adult red spider mites per day
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Red spider mites can cause untold damage to crops, particularly tomatoes. The tell-tale webbing usually means there is a large infestation
Biological control for indoor plants Steve andVal Bradley explain the biological methods for controlling red spider
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mite and whitefly that involve the use of predatory mites and parasitic wasps
52 AMATEUR GARDENING 19 JUNE 2021
whole pest population with one or two applications of a chemical. Biological control is actually about pest management, rather than outright control, so the aim is to keep the pest population at a manageable level, rather than eliminating it altogether. If the pest population disappears completely, the control agent will die out, too, due either to a lack of food or a disrupted lifecycle. So, the aim is to have a balance at all times, with a
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IOLOGICAL pest control is a ‘bug eats bug’ approach that involves the use of natural enemies to help control pests on your plants. There are predators for almost all situations now, not just outside in the garden but also in enclosed places such as indoor rooms, conservatories, greenhouses and polythene-clad structures where edible plants may grow alongside ornamental and tender ones. Selective organic control This method of pest control is suitable for organic gardeners and anyone who is reluctant to use pesticides, especially indoors or on plants being grown for food. The predators or parasites are bred to be host-specific, so they will only prey on the insect pest you wish to control and are harmless to other wildlife and pets. Management not elimination Dealing with pests biologically is quite different from the traditional practice of aiming to wipe out the
Red spider mites are tiny sap-sucking insects that thrive in warm conditions
low population of pests supporting a low population of control. The two ways biological controls work 1. The pest is controlled by introducing insects that are predators and feed on the targeted pest, often eating adults, young and even eggs. This is the case with red spider mite control. Some predators can feed on other things, such as pollen or dust on the leaves of plants, so they can survive for a time even if the pest is only present in low numbers. 2. The pest is controlled by introducing a parasite, where the control will lay eggs in the pest at some stage of its lifecycle, usually the eggs or young. The predator’s young develop inside the pest, killing it. This is the case with whitefly control.
n Other pests that can be controlled biologically Citrus red spider mite, fuchsia gall mite, fungus gnats, mealybugs, scale insects, thrips
