H. Yunis et al., QUALITATIVE APPROACH FOR MODELING OUTBREAKS OF GRAY MOLD EPIDEMICS INNONHEATED CUCUMBER GREENHOUSES, Crop protection, 13(2), 1994, pp. 99-104
Disease records and microclimatic parameters were analysed in order to
develop a model for predicting outbreaks of grey mould (Botrytis cine
rea) epidemics in non-heated cucumber greenhouses. A quantitative stat
istical approach failed to produce a reliable model. However, when emp
loying a qualitative approach, an accurate, biologically sound predict
ion model was developed. Outbreaks of grey mould occurred when, on a w
eekly average, the wetting period of the foliage exceeded 7 h day-1 an
d the duration of temperature in the range of 9-21-degrees-C during th
e night (18:00-08:00) exceeded 9.5 h day-1. Data recorded in two growi
ng seasons were used to construct the model and its predictions were e
valuated with an independent data set. Controlled-environment experime
nts provided biological interpretations for these greenhouse-originate
d thresholds: when free moisture was present, germination of B. cinere
a spores occurred within 7 h; the period during which the pathogen is
exposed to environmental microclimatic influences (germination and pen
etration) is 9-10 h. The potential for outbreaks of grey mould epidemi
cs in commercial greenhouses could be reduced by restricting the wetti
ng period to <7 h day-1 by measures such as ventilation and heating.