Modelling the effect of the grapevine growth and susceptibilityon the dynamics of a powdery mildew epidemic

Abstract: Simulations are performed to explore the sensitivity of epidemics of powdery mildewof grapevine to variation of parameters related to the pathogen, the plant growth or the cropmanagement. For early inoculation, the three parameters linked to the sporulation (t), thedispersion process (cid) and the plant vigour (vig) are the most discriminating. The parameter ofontogenic resistance (τ) is less discriminating, and the height of shoot topping and the distancebetween buds are not discriminating. We also examined the relationship between vine vigour anddisease variables at key periods in the epidemic process. An increase of the parameter of vigourfrom 0.2 to 1 amounted to a higher number of leaves at flowering (Nflo) and a higher rate ofleaves emergence (RLE). The RLE was correlated with the rate of diseased leaves emergence andwith the severity of the disease at shoot topping, whereas Nflo was correlated to the diseasedleaves area at day 240. The percentage of young leaves during first sporulation event (s1s2) wascorrelated to the rate of shoot development (RDS). These two variables from host allowed todiscriminate the years. The duration and dynamic of infectious tissue can considerably varyfunction on the development of secondary shoots therefore on the climatic conditions and vigour.