For the Level 2 exam you need to know one example of each of: biological, chemical, physical (or cultural) and integrated methods of pest and disease control.
Example of Biological Control – ‘Nemaslug’ is a biological control treatment specific to slugs, with no adverse effect on other types of animal. Nemaslug is a microscopic nematode that is watered into the soil. The nematodes (Phasmarhabditis hermaphrodita) enter the slug’s bodies and infect them with bacteria that cause a fatal disease.
Example of Chemical Control – Deltamethrin. A broad-spectrum, contact insecticide used to control pests including aphids, whitefly, caterpillars, codling moth, plum moth, raspberry beetle, flea beetles, weevils, sawfly larvae, leafhoppers, capsid bugs, scale insects and mealybugs.
Example of Physical (cultural) Control – Polythene barrier: You can protect vulnerable carrot crops from carrot flies by surrounding them with 60cm (2ft) high barriers made of clear polythene to exclude the low-flying female flies, or covering the plants with insect-proof netting, such as Enviromesh.
Click here for an interesting guide to Natural Pest and Disease Control produced by Garden Organic.
Integrated Pest Management (IPM) – the key to a successful IPM programme is to understand the life cycle of the pest. This then allows us to see the pest’s lifecycle and in doing so we can devise ways of preventing it. IPM uses a range of control strategies to provide the most complete control of a pest or disease, integrating biological, physical, cultural and chemical approaches.
So a typical IPM programme will involve a range of approaches, for instance: selecting resistant species where they are available, cultural measures, biological control, and as a last resort, if a suitable compound is available, chemical control. It has been shown that combining a range of approaches produces much more effective overall control of the pest than using just one approach alone.
Here is an example of an IPM programme for Cabbage Root Fly:
Selection – Consider if there are any varieties resistant to the pest in question. there is currently no variety of cabbage developed with resistance to cabbage root fly, although some varieties are resistant to club root.
Cultural – If you are purchasing cabbage seedlings rather than growing from seed, ensure these are purchased from a source that is free of root fly.
Recent transplants can be afforded some protection by placing a brassica collar around the base of the stem. These can be bought from garden centres or they can be made from circles or squares, about 8-15cm (3¼-6in) across, using carpet underlay, roofing felt or cardboard. The collar prevents the female fly placing eggs in the soil surface close to a host plant. Eggs deposited on the collar often dry up and fail to hatch.
Plants can also be protected by growing them under the cover of horticultural fleece, or an insect-proof mesh such as Ultra-Fine Enviromesh.
Horticultural fleece may be preferred for seedbeds as it also will warm the soil.
Crop rotation is important, otherwise cabbage root flies will emerge from overwintered pupae in the soil under the fleece cover if host plants are grown in the same piece of ground in successive years. You should also not grow cabbages in the same soil in which you grew other brassicas the previous year.
During autumn the ground can be turned over and the grubs left exposed to be picked off by birds.
Biological – Nemasys Grow Your Own is a mixture of pathogenic nematode species that can be used to control cabbage root fly larvae and other pests, including the larvae of carrot fly, onion fly, leatherjackets, chafer grubs, sciarid flies, caterpillars, gooseberry sawfly, thrips and codling moth.
Chemical – None of the pesticides currently available to amateur gardeners are suitable for use against cabbage root fly.
Fundamental to a successful IPM programme is a good understanding of the pest’s lifecycle and behaviour. By understanding the lifecycle the grower is able to see points at which the pest is vulnerable and can develop strategies that attack the pest at that point. It is this concept, for example, that allows us to see that the collars will work to control the cabbage root fly.
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