Natural Crop Protection in the Tropics: Plant disease control

Plant disease control

The fungus Pythium debaryanum causes damping-off disease in a number of legumes and vegetables. While Fusarium oxysporum spp. cumini causes wilt in tomatoes, potatoes and other Solanaceae crops, Macrophomina phaseolina causes charcoal rot, a typical stress-induced disease.

Soil-borne diseases

Ash & castor oil

A mixture of ash (2–3 kg) and 1 litre of castor bean oil is prepared and spread on a seedbed of a size of about 100 m2. This application is repeated 2–3 times at intervals of 7–10 days. This method is successfully practised in tobacco nurseries in India against soil-borne diseases.

Slaked lime

Honduran farmers combat damping-off, caused by Pythium debaryanum, by applying a small handful of slaked lime at the base of each tomato plant showing signs of this disease.

Solarization

Cover the soil with transparent polyethylene sheets for about 15 days for the control of the soilborne pathogens Fusarium oxysporum spp. cumini causing wilt and Macrophomina phaseolina causing dry root rot. The control effects reached a soil depth of up to 30 cm. The reduction in pathogen populations persists into the second year after solarization. In a field experiment, the control effect increased when the plots received irrigation and fertilizer (e.g. farmyard manure) prior to the solarization. Higher soil moisture increases the sensitivity of the resting structures of the pathogens to heat treatment. In hot arid regions the solarization effect can even be achieved without polyethylene mulching if manured soils receive irrigation during the hot season. This practice, however, has to be weighed against a potential salinization effect. A significant control of these pathogens could be reached, thus leading to an improvement in crop yield. This practice further is effective in controlling weeds in the standing crop, the reduction being greater in the wet solarized plots.

Seet treatment with sour buttermilk

Sunflower seeds are soaked in sour buttermilk overnight and dried prior to sowing. It is observed that sour buttermilk helps to increase the growth of the plant and the size of sunflowers. The larger the size of the flowers is, the greater will be the harvest of seeds per plant.

Seet treatment with sweetflag powder

Boil 10 litres of water and cool it. Next morning, add 4 litres of cow's urine and 200 g of rhizome powder to the cooled water. Stir it well. Then add the seeds which are to be sown to this solution and mix it well. Remove the damaged seeds which float on the surface of the solution. Allow the remaining seeds in the same solution for 15 minutes. Filter the solution and separate the seeds. These seeds can be sown directly in the field. This gives protection and resistance against pathogens and pests. 1 litre of cow's urine and 50 g of rhizome powder is required for treating 1 kg of seeds.

Drumstick Tree

Moringa oleifera

The leaves of this tree contain crystalline alkaloids that inhibit the growth of Pythium debaryanum, the cause of damping-off disease in a number of legumes and vegetables. Incorporating leaves into soils planted to susceptible seedlings should put the disease under control. After incorporation, allow the leaves to decompose for about 1 week during which the active compounds are released before the crop is planted.

The printed version contains more information about the following themes:

Plants with fungus - controlling properties

Plants with virus - controlling properties

Other methods