natural-products-in-plant-pest-management

110 L.A. Shcherbakovaand availability of effective agrochemicals, a number of problems are facedin managing the diseases successfully. The resistant cultivars provide onlypartial plant protection from a disease because of the occurrence of newpathogenic races that are able to overcome the resistance. Sometimes, breedingfor resistance is too complicated because of the diversity and high variabilityof plant pathogens and the variety of defence responses at differentstages of pathogenesis and plant development.Chemical protection gives a powerful tool for effective control of manydisease-causing agents, but its implementation has a range of undesirableside impacts. Thus, the use of chemical pesticides is associated with environmentalrisks, such as pollution of soil, water and crop plants with xenobioticpesticide residues, killing beneficial microorganisms or insects,thereby interfering with the natural management of pests and pathogens,a reduction in biological diversity, and so on. Sometimes, chemical pesticidesare not always effective and many treatments with several fungicidesare needed to control some fungal pathogens. As a result of continualpesticide application on plants and stored agricultural products, toxic residuesof chemical pesticides may appear and accumulate in food. Lastly,perhaps the most disturbing consequence of chemical protection is thedevelopment of pesticide resistance in pathogens that makes a protectiveeffect changeable and insufficiently effective. The health and ecologicalproblems related to chemical pesticides are now receiving a great deal ofattention. Recognition of these problems has created the phenomenon ofgreen consumerization.The biocontrol of phytopathogens as an additional or alternative plantprotection method looks more natural and environmentally compatible thanchemical treatments. The use of non-pathogenic or beneficial microorganismsand/or natural compounds, which are native and biodegradable in theenvironment, is the main objective of green consumerization. A few hundredbiocontrol products based on numerous beneficial strains predominantlyof Trichoderma, Bacullis, Pseudomonas, Agrobacterium, Streptomyces andGliocladium species are produced, commercialized and used as biopesticidesand/or biofertilizers.Natural compounds effectively controlling plant pathogens and pestsare represented by a diversity of substances belonging to different chemicalclasses and produced by a wide range of living organisms (Varma and Dubey,1999). Currently, the list of these natural compounds is growing longer fromyear to year. Many natural products have already been used or recommendedas biopesticides (e.g. various secondary plant metabolites such pyrethrins,glucosinolate-sinigrin-producing allyl isothiocyanate, carvone, azadirachtin,rotenone, ryania, nicotine, some essential oils and other volatile plant substances).The plant-mediated mode of action of some natural compounds,which does not establish contact with pathogens, decreases the risk of resistantpathogenic form selection. Because the search for natural substances fittingphytosanitary regulations and environmentally compatible croppingmethods is a continuous active process, novel compounds are being discoveredin plants, animals and microorganisms and are marketed in place of