Abstract
Kunimoto, Y., S. Nishino, J. Otuji, and T. Arima, 1997. Seasonal occurrences and vertical distribu tion of the two-spotted spider mite on chrysanthemum J. Acarol. Soc. Jpn., 6(1): 11-16.
Seasonal occurrences of the two-spotted spider mite, Tetranychus urticae Koch, were investigated on two cultivars of chrysanthemum from April 1993 to April 1994. Mite infestations were also surveyed on weed plants in surrounding areas.
1. Mites were found on several weed plants.
2. On the cultivar“Koyo”and“Lincoln”, the seasonal occurrence of mites was unimodal, but the peak duration was different between the two cultivars.
3. When a chrysanthemum was cut from the mother plant, some mites were left on the cuttings and maintained their populations. Mites returned to the field from the nursery when rooted cuttings were planted in the field.
4. Mite density increased rapidly in July and remained at a high level until September. The density then decreased gradually until February, but some survived throughout the winter.
5. Spatial distribution of mites expanded with growth of the chrysanthemums.
