P-241 - Balancing the Disease Triangle: Inoculum Concentration, Host Susceptibility, and Environment on Pestalotia Leaf Spot and Fruit Rot of Strawberry

Neopestalotiopsis has become a concern in strawberry production after recent outbreaks of Pestalotia leaf spot (PLS) and fruit rot (PFR). This study evaluated over two seasons the impact of inoculum concentration on two cultivars with different susceptibility, and the effect of inoculum carryover on worker hands after harvesting. ‘Florida127’ (highly susceptible) and ‘FL 16.78-109’ (moderately susceptible) were inoculated with 10, 10², 10³, and 10⁴ conidia/mL. In year one, conducive conditions led to an incubation period (IP) of 5 (Florida127’) and 10 (FL 16.78-109’) days at the highest inoculum concentration. PLS incidence was >72% in both cultivars for inoculum >10³ conidia/mL, while PFR was 61% on ‘Florida127’ and 21% on ‘FL 16.78-109’. In year two, less favorable environmental conditions extended IP at 10⁴ conidia/mL to 8 (‘Florida127’) and 44 (‘FL 16.78-109’) days. PLS incidence reached 94% in ‘Florida127’ and 51% in ‘FL 16.78-109’, with PFR of 33% and 25%, respectively, at 10⁴ conidia/mL. Disease increased for inoculum >10³ conidia/mL in year one on both cultivars, while only 10⁴ conidia/mL differed from the non-inoculated control on ‘FL 16.78-109’ in year two. No significant disease was observed for 10 and 10² conidia/mL in either cultivar or year. Inoculum carryover of >3000 CFU/glove was recovered in year one, but the maximum was 400 CFU/glove in year two. These findings highlight the importance of reducing Neopestalotiopsis inoculum and better cultivar tolerance for integrated disease management and the role of the environment.