The frequency of occurrence of Grapholitha molesta( Busck) in single pear,peach and mixed pear-peach orchards in Laiyang

In order to clarify the frequency of occurrence of Grapholitha molesta( Busck) under different planting patterns including pear orchards,peach orchards and mixed pear-peach orchards in the Laiyang area,pheromone traps and an effective cumulative temperature model were used to forecast the number of generations of G. molesta in 2009-2012. The results show that: G. molesta has 4 generations per year in the Laiyang area. From April to August,the 1st-3rdgenerations mainly occur in peach orchards whereas the 4thgeneration occurs in pear orchards from August to September. The last generation disappeared in the middle of October. The occurrence time of G. molesta on different hosts varied. In pear or peach orchards G. molesta can complete 4 generations. The 1st-3rdgenerations were more numerous than the 4thgeneration in peach orchards. On the other hand,the 1st-3rdgenerations were less numerous than the 4thgeneration in pear orchards.