Factors affecting the presence of Typhlodromusspp. (Acarina: Phytoseiidae) in the calyx cavities of apple fruits and implications for integrated pest management
Predatory mites of the family Phytoseiidae include several species of importance as biological control agents of phytophagous mites in various crops including apples. We report on the post-harvest presence of the motiles of two species, Typhlodromus occidentalis and Typhlodromus pyri, in the calyx cavities of apple fruits of three cultivars. The mean numbers of motiles per fruit were as high as 6.10. The phytoseiid densities were lowest in cv. Bonza and tended to be greater in samples taken in late autumn, particularly in cv. Red Delicious. No significant effect (p > 0.05) was observed for different insecticide treatments. Phytoseiids remained present within fruits of cv. Granny Smith left on the orchard floor in winter. Together with an observed reduction in the numbers of T. occidentalis in the early spring, this suggests that fruits constitute an overwintering refuge. The findings are discussed in relation to the implications for biological control, in particular the minimization of the removal of natural enemies from orchards.
Overwintering Females and the Number of Generations of Typhlodromus (T.) pyri Scheuten (Acarina: Phytoseiidae) in Nova Scotia
Typhlodromus pyri Scheuten (= T. tiliae Oudms.) is the predominant species of predacious mite on apples in Nova Scotia. It feeds on a wide range of prey species (Herbert, 1959). Chant (1960) investigated the life-history and habits of this species in southeastern England and Herbert (1956) studied its life-history under controlled laboratory conditions. A knowledge of the life-histories of various components of the fauna is basic to an evaluation of predation; therefore, a study of the life-history and habits of T. pyri in the field was undertaken. This was supplemented by a laboratory study in which an attempt was made to duplicate field temperarures. The results of these studies are presented here.
Evaluation of Lapping Grains based on Shape Characteristics.
The shape and size of abrasive grains during lapping varies complicately and irregularly. In this study, the aspect ratio of grain size and the fractal dimension of the grain external form were used as shape characteristics of grain in order to evaluate grains with lapping time. The results obtained are summarized as follows : (1)The fractal dimension increases due to microscopic fracture and decreases due to macroscopic fracture or attritious wear. (2)The aspect ratio and the fractal dimension, which are grain shape characteristicsis of the macroscopic shape and the microscopic surface complication of grain respectively, can be used for evaluating grain shape variation during lapping.