What secret holds the fog? Testing the fate of biologicals from the nozzle to the plant surface

Abstract: Low volume and ultra low volume spraying (also known as fogging) is considered a more efficient method for pesticide application in greenhouses compared to the classic hydraulic or mechanical techniques. Automated systems require less applicator time to treat a large area while concurrently minimizing risks of worker exposure. In addition, manufacturers of low volume equipment claim that the sprays cover plant surfaces more evenly, reach areas that are usually missed (especially the underside of leaves), and reduce waste by avoiding run off. As living organisms, microbials (e.g., bacteria and fungi) are more sensitive to abiotic factors than chemicals. High temperature and pressure can negatively affect these microbes, yet these factors are integral to the transformation of microbial suspensions into droplets ranging from ~ 10-70 μm in diameter, depending on the spray system used. Aware of these challenges, we tested microbial agents and low volume spray equipment to answer the following questions: Does fogging reduce the fitness of the propagules? Does it decrease the viability (and ultimately efficacy) of the biological control agent? How many infectious units reach their target? Today growers can choose from many products and machines for the application of microbial products. Results presented here will help growers select the right low volume machines.