Abstract: Based on the long term (1999-2008) monitoring of air temperature and relative humidity and of the occurrence and epidemiological trend of Marssonina blotch in the main apple-production area of Shaanxi Province, this paper analyzed the occurrence time, pathogenesis regularity, and epidemiological level of Marssonina blotch, with the 1- and 3-dimensional models for predicting Marssonina blotch under effects of ten-day mean air temperature (T) and relative humidity (Hm) constructed. In study area, the development of Marssonina blotch was mainly affected by environment factors. This disease spread rapidly in field in July and August, causing orchard defoliation, and the harm persisted until September. After the first frost, new disease spots no longer developed. The data of T and Hm in the models showed a good fitting with field condition. The 3-dimensional dynamic prediction model of Marssonina blotch was f(T,Hm)=-0.0172T³+0.9497T²-16.2209T+88.9923-0.00001Hm³+0.00354Hm²-0.15554Hm+2.36578, where f(T,Hm) was disease index. The modeling results showed that the T  for the occurrence of Marssonina blotch in field was 15 ℃, and the disease would have an epidemic peak when the T and Hm in July and August reached 23 ℃ and ≥90%, respectively.

Key words: apple Marssonina blotch, 3-dimensional dynamic prediction model, environment factors