Abstract
The importance of seed treatments has increased rapidly in the past decade, mainly due to their high efficacy controlling early-season pests and diseases, and their limited environmental impact. Chemical seed treatments require a smaller amount of pesticide use and reduce environmental spread compared to foliar or soil applications; similarly, selection pressure for the development of resistance in the pest population is reduced. However, the rapid dissipation of seed treatment active ingredients after planting is associated with unpredictable duration of control, limiting the performance of seed treatment technology. Polyanhydrides are synthetic biodegradable polymers that can be used to deliver active ingredients or pharmaceuticals in pathological systems. They can provide a steady and sustained release of active compounds, enhancing the treatment of diseases caused by pathogens. Our study consists of experiments using polyanhydride nanoparticle-encapsulated fludioxonil and thiabendazole (two fungicides commonly used against Fusarium graminearum) at different rates on maize and soybean. We employed both rolled-towel assays (simulating a seedborne infection) and delayed emergence assays (simulating a soilborne infection). In the rolled-towel assay, nanoparticle-encapsulated fungicides performed similarly to standard formulations. However, when emergence was delayed for one week by low temperature, nanoparticle-encapsulated fungicides showed superior control over standard formulations. For longer emergence delay treatments, nanoparticle and conventional fungicide formulations showed similar levels of control. Polyanhydride encapsulated seed treatments showed the potential to prolong effectiveness of active ingredients when emergence is delayed due to cold temperatures, a very common situation in temperate maize production areas, such as the American Midwest.