Responsive Polymers for Crop Protection

This review outlines the responsive polymer methods currently in use with their potential application to plant protection and puts forward plant-specific mechanisms as stimuli in newly devised methods for smart release of crop protection agents (CPAs). CPAs include chemicals (fungicides, insecticides, herbicides), biochemicals (antibiotics, RNA-based vaccines for plant viruses), semiochemicals (pheromones, repellents, allomones), microbial pesticides, growth regulators (insect and plant) or micronutrients, all with crop protection effects. This appraisal focuses on emerging uses of polymer nano-encapsulated CPAs. Firstly, the most interesting advances in controlled release methods are critically discussed with their advantages and drawbacks. Secondly, several plant-specific stimuli-based smart methods are anticipated for use alongside the polymer nano- or microcapsules. These new CPA release methods are designed to (i) protect plants against infection produced by fungi or bacteria, and (ii) apply micro-nutrients when the plants need it the most. Thus, we foresee (i) the responsive release of nano-encapsulated bio-insecticides regulated by plant stress enzymes, and (ii) the delivery of micro-nutrients synchronized by the nature or intensity of plant root exudates. Such continued advances of nano-scale smart polymer-based CPAs for the protection of crops herald a small revolution for the benefit of sustainable agriculture.