Seed Pretreatment as a Means to Achieve Pathogen Control

Abstract

Seed treatment is the first and basic technique being practiced for seed protection since long. Chemicals and biological agents are applied to protect seeds from microbial pathogens and insect pests. The application of seed treatment is being evolved to more environment-friendly compositions as the time passes. Purposes of seed treatment are to reduce the economic losses to the crop due to pathogens and avoid development of resistant pathogen races and reduction of pesticide residues in the product. The purpose of the seed treatment is to avoid the pathogen attack and protection of seeds and seedlings. Application of chemicals at the early stage has an advantage of effectiveness of low dosage as the pathogen is very vulnerable because the seedborne stage is the weakest part of the life cycle of microbes. On the other hand, the disadvantages include the possibility of accidental poisoning, limited dose capacity, shorter shelf life of the treated seeds, and exposure of the worker to the chemicals when treating larger quantities of seeds. Major fungal diseases including bunts, water molds, rots, and damping-off and bacterial diseases including rots and wilting are commonly controlled by applying chemicals. A few viral diseases are transmitted by the soilborne fungal pathogens that may result into a major problem at the later stages and must be controlled at early crop stage by application of seed treatment of their fungal vectors. Soilborne insects like rootworms, maggots, and wireworms are to be controlled at the sowing stage. To control these pathogens, several biological agents like Bacillus subtilis, Streptomyces griseoviridis, and Trichoderma harzianum are also used along with the synthetic chemicals. The chemical applications are done using carboxin, difenoconazole, fludioxonil, imazalil, mefenoxam, tebuconazole, thiabendazole, and triadimenol. The insecticides commonly used for the seed treatment are chlorpyrifos, imidacloprid, permethrin, and thiamethoxam. Several additives including colors, antifoaming agents, lubricants, carriers, and micronutrients are also used to enhance the efficiency of the seed treatment. Application of biological and chemical treatments at the early stage of the crop is playing a helpful role in maintaining the healthy crop and harvesting an improved yield.