HLB is known to make citrus roots more susceptible to Phytophthora root rot. It also reduces the efficacy of chemical management of Phytophthora root rot, creating a difficult management scenario. Current Phytophthora management recommendations are based on pre-HLB work done in the 1980s. These three conditions raise the question of whether yield improvement from Phytophthora management is enough to pay for the management costs themselves. The goal of this project is to develop new soil propagule density managment thresholds and recommendations for chemical management of Phytophthora root rot based on ecomonic analysis of yield responses in different soil conditions. We have identified multiple field sites with heavy and moderate Phytophthora infection and have begun plotting field maps to get the yield data where possible and begin treatments as the weather warms. Due to an observance of substantial brown rot in some of the groves we have been scouting without highly conducive weather and only with the severe (for brown rot) P. nicotianae, we will also include brown rot ratings and compare this in Valencia and Hamlin groves to include this in our economic analysis. We are considering adding a split plot factor of foliar brown rot sprays. Meanwhile we are planning an additional greenhouse Phytophthora and HLB experiment to determine if the newly labeled chemistries have the same limitation on HLB-affected plants as fosetyl-Al and mefanoxam have shown. Seedlings for these trials have been started and will begin when the weather warms in the spring. Many of the new chemistries are directly effective against Phytophthora in the soil rather than acting after uptake by the roots, so this is likely to reduce the limitations of Phytophthora management in HLB-affected groves and test the hypothesis