Monitoring conidial density of <Emphasis Type="Italic">Monilinia fructigena</Emphasis> in the air in relation to brown rot development in integrated and organic apple orchards |
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| Authors: | Imre J Holb |
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| Institution: | (1) Centre of Agricultural Sciences, University of Debrecen, P.O. Box 36, H-4015 Debrecen, Hungary |
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| Abstract: | 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. |
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| Keywords: | Aerial spore density Apple Brown rot fungi Disease incidence Epidemiology Integrated Monilinia fructigena Organic Spore dispersal Viability Weather variables |
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