P-569 - Efficacy of pre and postharvest fungicides in controlling Neonectria fruit rot of pome fruit

Neonectria Fruit Rot (NFR), caused by pathogens Neonectria spp., affects pome fruits in the United States and globally. Infections occur preharvest but remain latent, with symptoms typically appearing after several months of storage. This study assessed the efficacy of four pre harvest fungicides, i.e., triflumizole, fluopyram + pyrimethanil, fluxapyroxad + pyraclostrobin, Polyoxin D zinc salt, and four postharvest fungicides, i.e., thiabendazole, pyrimethanil, fludioxonil, and a mixture of fludioxonil + difenoconazole. D’Anjou pears and Fuji apples, harvested at commercial maturity, were wounded, treated with the fungicides at the label rates, and inoculated with spore suspension of two Neonectria sp. isolates at 10⁶ spores/ml. Four replicates of total 20 fruit were used for each isolate and host. Apples and pears were stored at 1.5 and 0.5°C, respectively, and disease incidence and severity were assessed monthly. Preliminary results Neonectria sp. is more virulent on pears than on apples. After four months of storage, thiabendazole and fludioxonil were the most effective as they reduced disease incidence to 38-57% and 42-75%, respectively. By five months, efficacy declined significantly on pears with only thiabendazole providing some reductions between 20 to 50%. On Fuji apples, the disease severity remained low across all treatments. These preliminary findings indicate a high risk for fruit loss due to the limited efficacy of many pre and postharvest fungicides against Neonectria spp.