When rains come, farmers rejoice because it is a good thing. But even with this blessing called rains, there’s a downside. Excessive moisture can cause a number of problems for gardeners — crop diseases.
Most diseases caused by bacterial and fungal pathogens require free moisture to survive on leaves and other plant parts. Such conditions occur especially in vegetables, flowers and fruit crops. Most plant diseases cannot be cured but only controlled once a plant is infected.
Early detection and prevention is the key to managing plant diseases. The diseases will manifest by producing abnormal plant growth. Infected plants often show one or more of the following symptoms — stunting, spots on leaves, stems or fruits, discolouration of plant parts, decay or rots on leaves stems, or fruits, wilting, and/or rapid death and collapse of entire plants or plant parts.
Most leaf spot diseases are specific, only capable of infecting a few species of plants. When a plant in your garden develops leaf spot, you usually do not have to worry about it spreading to everything in your garden. It is worth noting that a disease is likely to spread to plants of the same type from one tomato bush to the next. Pruning and spacing plants to promote good air circulation will help them dry off more quickly following rainfall and can reduce leaf spot problems. Removing spotted leaves from plants will help slow the spread of the disease but will not cure it.
If the older leaves on your plants are simply turning yellow, with no spots, they are most likely showing symptoms of nitrogen deficiency.
Nitrogen leaches out of the soil rapidly with heavy rainfall, leaving fast growing plants like flowers and vegetables hungry. If the plants in your garden are losing lots of yellow leaves, you should fertilise with a slow release or organic fertiliser to replace the nitrogen lost due to rains. In addition, watering plants with a liquid fertiliser also helps. Plant roots need oxygen to survive, especially the tender root hairs that are responsible for absorbing water and nutrients from the soil.
Oxygen exists in soil in the small air spaces between soil particles.When these spaces fill up with water, delicate root hairs drown. As a result, plants wilt particularly during the heat of the day. This is often a temporary problem, and plant roots are able to recover as long as the soil dries out within a day or two.
When the soil stays wet for an extended time, root rot diseases are likely to set in. With these diseases, once a plant wilts it does not recover but gets progressively worse. There is no way to save infected plants or eradicate these diseases, which live in the soil. In wet areas, only varieties that are moisture tolerant and known to be resistant to root rot diseases should be planted. Learn how to identify these symptoms. Frequent monitoring of the crop to scout for disease outbreak is a sure step towards controlling and preventing the diseases early before they turn into a calamity.
A number of fungicide can be applied depending on the case at hand. However, fungicides are most effective when they are applied prior to or early in the development of diseases.
Apart from the chemical means, farmers can employ a number of non-chemical techniques to help in prevention of plant diseases.
What to do
Fertilise your plants, strong healthy plants are generally more resistant to disease than unhealthy plants. Choose your planting site wisely. Choosing diseases resistant varieties is another sure way of overcoming plant diseases during wet weather. Consult your agro dealer for these varieties.
You may also write to Smart Harvest for any inquiries. Pruning and staking can also improve aeration around the plant foliage reducing the time that leaves and stems remain wet after rainfall. This is common in tomatoes. Many diseases can be easily spread from plant to plant when leaves are wet. Planting on raised beds or mounds is advisable. This improves drainage as the raised plants are not affected by floods.
The writer is an expert on sustainable agriculture