2002-2004 Specialty Crops Research Program
University of California

Principal Investigators: Themis J. Michailides

Project title: Efficient Determination of Spore Inoculum Potential of Brown Rot Pathogen
(Monilinia fructicola) in Stone Fruit Orchards by Using Molecular Techniques

Heavy use of pesticide application is one of major reasons causing air, soil, and water pollution. Although chemical control of brown rot of stone fruit is still an important control strategy, avoiding unnecessary sprays becomes critical in stone fruit production. We have established a Decision Support System for IPM of Prune Brown Rot (DSS-PBR at hppt://tjm.uckac.edu) to guide growers in disease management by determining the proper fungicide application timing. The inoculum potential in orchards is an important variable considered in this system to determine the possible risks of blossom blight, latent infection, and fruit rot. Although some experimental data were used in the development of this system, accurate estimation of inoculum potential of the brown rot causing pathogen, Monilinia fructicola, needs to be improved. Spore density in the air could be determined by using spore traps. However, reading samples’ data with a microscope is time consuming and subject to errors. In this project, we propose to establish molecular approaches by using the real-time PCR techniques to quantitatively detect the spore density of M. fructicola of spore samples collected in the air of stone fruit orchards. We propose to conduct 2 years of field experiments in 10 stone fruit orchards in California and determine the proper time of spore trap sampling to estimate inoculum potential and microclimatic conditions favorable to blossom blight. The experimental data will also be used to determine the critical and important period for estimating inoculum potential in the mid-season to estimate risk of latent infections. Our existing DSS-PBR will be improved by using the anticipated results. The expected molecular techniques will be used to determine the inoculum potentials in stone fruit orchards geographically.