Diseases on your vegetables can cause loss of yield and damage to vegetables, which reduce the quality of your harvest. With warmer weather most smallholders are already seeing steady growth in vegetable patches and gardens.

Knowing what to look for in terms of diseases in your plants is important in treating and preventing their spreading.

What spreads plant disease?

Diseases can be spread by:

  • insects;
  • rain splash and overhead irrigation, which usually spread diseases over short distances;
  • wind, which can spread diseases over long distances;
  • runoff and flood irrigation;
  • diseased seeds, seedlings and vegetative planting material which can spread diseases over very long distances, even between countries;
  • boots and other clothing of workers, and tractor or truck tyres;
  • equipment used in the garden (e.g. garden forks, hoes, pruning scissors);
  • plants left in the garden from the previous season.

The first step in preventing diseases is to have a good understanding of the “disease triangle”. Diseases can occur only when the following three components are present at the same time: a susceptible host plant, a pathogen capable of causing disease and an environment conducive to disease. Break the links in the triangle at any point and disease will not occur.

It is best to develop an integrated approach to the prevention and management of plant diseases. The foundation of this approach is simply looking: walk through the garden to identify problems. This needs to be done regularly, at least once a week but preferably more frequently.

Your integrated approach will focus on creating an environment for your vegetable plants to grow strong and healthy, so that hopefully the diseases will not be able to establish themselves or if they do, the plants will withstand their effects. An integrated approach also combines alternative control methods that help minimises the use of chemicals, thereby reducing health, environmental and economic risks.

Cultivation practices should include using disease-resistant cultivars, choosing crops according to the season and location, keeping plants healthy through proper watering, mulching and fertilising, practicing crop rotation to prevent build-up of diseases and applying companion planting, creating a well-balanced soil, using the correct spacing between plants within a row as well as between rows, removing infected plants from the growing area (e.g. plants infected with a virus disease).

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