MAJOR DISEASES OF CROPS AND RODENT MANAGEMENT

Damping-off Causal agents: fungi – Fusarium, Rhizoctonia, Pythium, Phytophthora sp

Signs and symptoms are the dry rot is usually the symptoms of this disease are brown, water-soaked areas around the lesion that shrivel and pinch the seedling off at the base. Limited to the outer part of the stem and infected plants may fall down or may remain more or less upright.

Natural enemies: Many successes have been reported with the use of Trichoderma sp. for the prevention of damping-off. The prevention activities Location: avoid placing the nursery in a densely shaded or humid place. Remove crop debris as it may contain spores of damping-off fungi (and other pathogens). Crop rotation: If you are raising cabbage seedlings every season, use fresh soil that has not been used for cabbage or other cruciferous crops for at least 2 years. Plant another crop (not a cruciferouscrop) in the ‘old’ cabbage nursery. When it is present Uproot and destroys diseased seedlings to avoid build-up of the pathogen population. When the nursery soil is wet or waterlogged, dig a trench around the beds to help the water flow away. It may slow disease spread to other parts of the nursery.

Black rot - Xanthomonas campestris

Causal agent: bacterium – Xanthomonas campestris

 

Worldwide, black rot is considered to be one of the most important diseases of crucifers. Its Signs and symptoms Leaves of affected seedlings turn yellow and drop off prematurely. On older plants, V-shaped yellow lesions appear at the leaf margins with the point of the V inwards. Prevention activities such as At least three years’ rotation of the seedbed and the transplanted field with non-cruciferous crops are advisable. It is advisable to sterilize seed in water at 50oC for 30 minutes before planting. That will kill bacteria that stick to the seed. See section 3.3. Control cruciferous weeds: they may be a source of infection. Once an infection is present Sanitation: after harvest, remove all infected plants with roots from the field and either place them on a compost pile, feed them to cattle, or burn them. This will reduce bacteria surviving in the field on infected crop debris.

Soft rot - Erwinia carotovora

Causal agent: bacterium – Erwinia carotovora

The common name of this bacterial disease arises from the characteristic soft decay of the fleshy tissue of the plant. When soft rot affects a plant, the tissue softens, becomes watery and slimy. Prevention activities such as Sanitation practices: make sure the field is clean from crop debris from a previous season. Also the borders of the field should be cleaned from crop debris. Avoid injury to the crop - the wounds can be entry points for the bacteria. And monitor field regularly and remove heavily infected heads from the field. Once an infection is present Lightly infected heads can be harvested and the affected leaves peeled off. Those heads can still be sold or used for home consumption. Its Signs and symptoms Dark slightly sunken spots develop on basal leaves near the soil. Prevention of weed (some tactics). “The best control is prevention” is also valid for weed management Mulching is a very good and very commonly used method for both weed prevention and weed control. Compost manures to reduce weed seed: animal manures may still contain weed seed.

                How to control weeds (Physical control). Handweeding is the oldest, simplest and most direct way of controlling weeds.  Ploughing the field will bury some weeds and cut others. Prepare seedbeds immediately before planting or sowing. Weeding can be done by hand or with some kind of hoe or other tool which will cut off or uproot the weeds.

RODENT MANAGEMENT

                Natural enemies of rats these include owls, cats, dogs, and many kinds of snakes (e.g. pythons). Some methods in management of rat (Before transplanting). Cut weeds along bunds and irrigation canals, looking for rat burrows which should be destroyed. Fumigation guns which use burning straw and sulfur area available in some areas for killing rats in their holes. (After transplanting) A sustained baiting programme is the best way for farmer groups to control rats. For sustained baiting, poisons which kill after several feedings are used. Some cultivation methods.  Use of cropping pattern which limits food supply and habitat for rats. For example, do not grow dry crops continuously. Do rotation cropping with rice. Cut weeds on bunds regularly, clean out bushes, level off hillocks and remove crop residues before the season and after harvest, to limit rat habitat. The mechanical methods Make use of all kinds of existing traps, simple to complicated ones, cheap, easy to find, effective in catching rats (live traps, snap traps, etc.). Use dogs to hunt rats. Combine with burrow digging, fogging and driving to catch rats. Put plastic fences around the field bunds (about 50 - 100 cm high) to prevent rat damage. It is very easy to do but it requires much investment for materials.