The emergence of adult male Grapholita dimorpha and their periods of infestation of apple orchards in central Iwate Prefecture were investigated from 2006 to 2008. Adult males of the overwintering generation, the first generation,and the second generation were caught using pheromone traps from late May to mid-June, from mid- to late July, and from mid-August to mid-September,respectively. No fruit damage caused by first- and second-generation larvae of this pest was observed in apple orchards, but apples infested by third-generation larvae were observed. Fruit damage caused by third-generation larvae was also observed in an orchard where mating disruption without insecticide spraying was practiced, possibly because second-generation adults flew to the apples of this orchard from other hosts such as plum trees growing nearby.

Plums damaged by Grapholita dimorpha were collected periodically and incubated at 25℃ under a photoperiod of 16L:8D to determine the oviposition and adult emergence periods. The extent of fruit damage was small until early July, which is the time when adults of the overwintering generation are estimated to oviposit, and increased from late July to early August, which is the time when adults of the first generation emerge and are estimated to oviposit. Insects in apples collected in early September were estimated to be oviposited from late August to early September, which is the time when adults of the second generation are caught on pheromone traps.

The occurrence of Grapholita dimorpha around apple orchards in the central areas of Iwate prefecture was investigated in cooperation with forecasting activities by apple farmers. G. dimorpha was found to be common in these areas,since adult males were caught at 21 of 23 sites by sex pheromone traps during the 2008 season. The total number and seasonal trend of captured individuals varied across years and survey points, although three prevalent periods could be recognized at several points where more than 100 individuals were caught in one season. In the apple orchards without chemical spray, fruit damage by G. dimorpha was observed only in September and October. The early generations of G. dimorpha were detected mainly on Japanese plum or European plum. Damage on apple in autumn could be ascribed to changes in the host preference of late generations of G. dimorpha.

The influence of weeding using burners around trunks on the population density of the two-spotted spider mite Tetranychus urticae on the apple trees was investigated. On the trees whose undergrowths were burned, mite density remained around two adult females per leaf for fifty days after burning. On the contrary, that on trees without burning increased rapidly up to six adult females per leaf in the same period. Before burning, the persian speedwell Veronica persica and red dead nettle Lamium purpureum were predominant in both test and control areas, which were infested with a large number of T. urticae. It seemed that elimination of undergrowths favorable to two-spotted spider mite by burning suppressed population growth on the trees through restriction of the vertical movement of two-spotted spider mite.