As the cost of chemical fertilisers and pesticides continues to go up, it is imperative that farmers know the alternative ways of controlling pests and diseases to sustain food production.
To begin with, plants have their own natural defence mechanisms against pests and diseases. Some produce aromatic substances that repel insect pests, others have sticky hairs that prevent insects from landing on them. In the recent past, breeders have developed crop varieties, cultivars or hybrids which are resistant to specific pests and diseases.
Farmers should choose varieties that are well-adapted to the prevailing environmental conditions (temperature, nutrient supply, pests and makes them stronger against infections of pests and diseases).
Use clean seed and planting materials (certified) from safe sources. Suitable cropping systems such as diverse cropping, crop rotation, green manuring and cover crops help.
Crop rotation helps to reduce the accumulation of pests and diseases because the pest or disease cycle is broken when a different crop is grown.
Diverse cropping involves growing of many types of crops. Instead of fertilisers, organic matter is used and it improves soil fertility, stabilises soil structure and supplies substances that strengthen the plant's own protection mechanisms.
The use of compost can reduce disease problems due to the presence of micro-organisms, which will compete with pathogens for nutrients reducing population of the latter. Weed control should be practised to eliminate weeds that serve as hosts for pests and diseases. Avoid the use of herbicides as this is not allowed in organic farming. Uprooting, shallow cultivation to remove weeds and mulching can be used to eliminate weeds.
Practice good water management if carrying out irrigation. Flood irrigation and water on the foliage encourages pathogen infections.
Seeds can be treated to control seed-borne diseases, and to protect them against pests and diseases in the soil. Seed treatment can be done by soaking the seeds in hot water of a temperature of 50-60°C, coating the seeds with a plant extracts like crushed garlic or by coating the seeds with antagonistic fungi. If seeds are purchased from recognised companies, then the farmer should take into consideration the type of chemical used to treat the seed because chemicals are not allowed in organic farming.
Curative crop protection
This is the control of a pest or a disease that has already attacked the crop. Different methods can be used to control pests and diseases and they include:
This is the use of living organisms to control pests and diseases and is a complex method and is least understood by most farmers. The living organisms vary from time to time and from one place to another. For biological control to be effective, the farmer should know the ecology of the specific pest or disease and the available predators for successful biological control. There are four categories of bio-control agents namely:
Predators such as spiders, lady beetles, ground beetles, and syrphid flies usually hunt or set traps to catch a prey to feed on.
Parasitoids of pests are commonly wasps or flies. Pathogens are entomophagous fungi, bacteria, or viruses that can infect and kill insects, causing a disease in pest organisms. Examples are Bacillus thuringiensis (Bt), and Beauveria bassiana.
Nematodes are commonly used insect-pathogens. Some nematodes attack plants (e.g. root-knot nematode). Entomopathogenic nematodes feed on insects in the soil and humid places.
Use of plant extracts or bio-pesticides: They work as repellents, anti-feedants, prevent laying of eggs or act as inhibitors (prevent development of different stages of the pests). Neem extract, which includes a mixture of leaves, seeds and bark contains a chemical that prevents feeding and growth. It can be used to control diseases such as powdery mildew and anthracnose. Pyrethrin is another plant extract, which is used and it interferes with the nervous system of the insects or pests thereby paralysing it. Other extracts include chillies, onion, garlic, stinging neetle, tobacco. They can be used to control spider mites and white flies.
This is the use of traps and handpicking of pests. Yellow sticky traps are used to control most flying insect pests like whiteflies. Tutasan traps are used to attract Tuta absoluta in tomatoes. Pheromone traps are used to attract males to the traps such that the females lay eggs which are not fertilised and this helps to reduce pest population.
Weed control: Weeds are controlled through cultivation, use of mulches, uprooting, and solarization. Biological weed control by use of insects to feed on the weeds and hence reduce their population.