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.
Photoperiodic Induction of Diapause in a Predaceous Mite, Metaseiulus occidentalis,
Adult females of Metaseiulus occidentalis (Nesbitt) (Acarina: Phytoseiidae) exhibited an imaginal, reproductive diapause when reared under 8 hours of light per day at 19°C. Diapause was concluded spontaneously when the females were maintained under these conditions. Total productivity was lower than normal when the females in diapause eventually oviposited.
Comparative Studies on Four Strains of Typhlodromus occidentalis (Acarina: Phytoseiidae). V. Photoperiodic Induction of Diapause
In geographical areas with differing seasonal cycles of daylength, many arthropod species have adapted an overwinter diapause response to critical photoperiods (Beck 1968). Among spider mites, Bondarenko and Hai-Yuan (1958) reported that geographical populations of Tetranychus urticae Koch from 60, 45, and 41 °N responded to critical photophases of 17, 12.5, and 12 hr, respectively, by entering diapause. Sapozhnikova (1964) and Hoy and Flaherty (1970) have suggested that, among phytoseiid species, photoperiod was a major factor controlling the induction of diapause in Typhlodromus ( Amblyseius ) similis (Koch) and Typhlodromus (as Metaseiulus ) occidentalis Nesbitt, respectively.