Monitoring conidial density of Monilinia fructigena in the air in relation to brown rot development in integrated and organic apple orchards

摘要

In a three-year Hungarian study, conidial density of Monilinia fructigena in the air determined from mid-May until harvest was related to brown rot disease progress in integrated and organic apple orchards. Conidia of M. fructigena were first trapped in late May in both orchards in all years. Number of conidial density greatly increased after the appearance of first infected fruit, from early July in the organic and from early August in the integrated orchard. Conidial number continuously increased until harvest in both orchards. Final brown rot incidence reached 4.3–6.6% and 19.8–24.5% in the integrated and organic orchards, respectively. Disease incidence showed a significant relationship with corresponding cumulative numbers of trapped conidia both in integrated and organic orchards, and was described by separate three-parameter Gompertz functions for the two orchards. Time series analyses, using autoregressive integrated moving average (ARIMA) models, revealed that the temporal patterns of the number of airborne conidia was similar in all years in both integrated and organic orchards. Conidia caught over a 24-h period showed distinct diurnal periodicity, with peak spore density occurring in the afternoon between 13.00 and 18.00. Percent viability of M. fructigena conidia ranged from 48.8 to 70.1% with lower viability in dry compared to wet days in both orchards and all years. Temperature and relative humidity correlated best with mean hourly conidial catches in both integrated and organic apple orchards in each year. Correlations between aerial spore density and wind speed were significant only in the organic orchard over the 3-year period. Mean hourly rainfall was negatively but poorly correlated with mean hourly conidial catches. Results were compared and discussed with previous observations.