Field crop production practices continue to change as growers evaluate new techniques and technologies to increase productivity. Plant diseases, unfortunately, present a challenge to producers by continuing to limit yields in all the crops. There are a multitude of crop production management decisions that producers must make throughout a growing season. Many of these decisions can influence the impact of plant diseases on yields.
Proper cultural practices that favor the development of vigorous seedlings and hardy, mature plants will help manage diseases or lessen their detrimental effects. Disease management is also aided by good agronomic practices such as proper seeding rates and seeding dates, balanced fertility, crop rotation, tillage, and weed control. In other words, the healthier a plant is, it is better able to still be productive, even in the presence of plant pathogens. Many disease-management decisions are made before planting. In most farming systems, the producer can do little once a disease becomes severe in his field.
Therefore, prevention is the first, and usually the only line of defence against disease. It is rarely economical to treat acreages with fungicides. The primary fungicide application method in field crops is seed treatment, where extremely low rates of active ingredient per acre are applied directly on the seed before planting in the soil.
Diseases are the direct result of three critical factors coming together at one time, which occurs when a pathogen attacks a susceptible plant under environmental conditions that favor the infection and growth of the pathogen within the plant.
The most common disease-causing agents or pathogens are; fungi, bacteria, viruses, and nematodes. The most critical environmental factors are soil and air temperature, moisture as rain or dew, relative humidity, soil fertility, and pH. Serious disease can occur on susceptible cultivars when environmental conditions are right for the spread of an aggressive pathogen. For instance, the fungus that causes leaf rust of wheat produces severe yield losses on susceptible varieties when spores are blown in on wind currents. Susceptible varieties may have as much as a 50 percent yield loss, whereas resistant varieties may have little or no yield loss.
The cornerstone to successful disease control is correct identification of the disease related problems on your farm. Producers facing specific disease problems can fine-tune their disease-control strategies to those few diseases encountered each year. Those with little experience identifying diseases should seek help from competent sources, such as SAU's, Research Institutes, KKV's, etc.