Andrew
Word from the market with AMA
Good plant health is the key vessel to better crop and high yields.
However, some factors affect plant health which include biotic factors such as pests and diseases and abiotic factors such as soil moisture, nutrients, light, oxygen and temperatures.
Excess supply or inadequate supply of the abiotic factors can have detrimental effects on plant health.
Taking a closer look at high temperatures currently being experienced at the beginning of summer 2021/22 farming season both the field crop and horticultural grower are presented with production challenges.
High temperatures can be a threat to plant health directly and indirectly. Direct effects include wilting, discolouration of the plant, senescence, desiccation, sun-scald and bolting. Indirect effects include the rapid multiplication of pests and diseases.
After crop establishment in field crops such as maize and soyabean high temperatures can be a threat to good plant health. The smart farmer must combine all technologies at his or her disposal to conserve moisture and maintain crop vigour. Cultural control factors include keeping the crop completely free of weeds. Weeds compete for sunlight space, nutrients, sunlight and water.
Weed control will mean that there is less competition for available soil moisture. Farmers can also make use of mulching. Mulching is one of the principles of conservation agriculture and a technique practiced in Pfumvudza plots. The use of crop residues as mulch will help conserve soil moisture. Furthermore, water harvesting techniques such as tie-ridging or potholing should be carried out. This will ensure that any rain received enters the soil and is not lost through run-off.
For horticultural growers who venture into tomato, pepper and eggplant production, sun-scald is a threat to yield. Growers should aim to maintain good crop foliage to reduce sun-scald. Growers under greenhouse production can make use of opening the vents to maintain the temperatures.
Farmers should be wise in variety selection and choose summer varieties that are less prone to bolting in crops such as onions and brassicas (cauliflower and brocolli). The choice of irrigation type will be a game-changer for the farmer.
Drip irrigation will ensure that water is applied directly to the plant and less water is lost to the atmosphere through evaporation.
There is rapid multiplication of pests such as aphids, red spider mite and Tuta absoluta which are a menace to production. Multiplication of red spider mite is robust and fast under conditions of high heat temperatures above 20 Degrees Celsius and low humidity of less than 50 percent. The red spider mite can complete its life cycle in just 5 to 7 days under these conditions producing many generations.
Aphids do not require males to produce offspring and they can give birth to live young ones at a faster rate when temperatures are high. Aphids are a threat to production as they are vectors of plant diseases. Farmers are recommended to scout their fields regularly and come in with control measures when the pests have reached economic threshold levels.
An Integrated Pest Management programme which includes cultural, physical, biological and chemical control measures will help the farmer obtain a better crop. Moreover, the farmer should use chemicals with different modes of action to avoid resistance.
Good agronomic practices at early crop establishment will lead to good plant health and at the same time favour a better crop and higher yields.
This article was written by Justice Chembela, ZFC Agronomist. Word from the market is a column produced by the Agricultural Marketing Authority (AMA). Feedback [email protected]; [email protected]; [email protected]
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