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Seasonal occurrence of phytoseiid mites on windbreaks of Podocarpus macrophyllus surrounding citrus orchards
To find effective native natural enemies of spider mites in the surrounding vegetation of citrus orchards, we investigated the species composition and seasonal occurrence of phytoseiid mites on Podocarpus macrophyllus, which is one of the major windbreak tree species surrounding citrus orchards in Japan, in Nagasaki prefecture, south-western Japan, from 2006 to 2007. Six species were found: Amblyseius eharai, Euseius sojaensis, Okiseius subtropicus, Typhlodromus vulgaris, T. kishimotoi, and Typhlodromus sp. Amblyseius eharai was the most dominant species and formed more than 60% of the phytoseiid species collected in both years. Typhlodromus vulgaris was the second most dominant species. The other species were rare, except that Okiseius subtropicus was abundant in February in 2006. The density of A. eharai showed two peaks in late June and from late August to early September. The density of T. vulgaris also peaked in late June. However, the density declined thereafter, and remained low, unlike the seasonal occurrence of A. eharai. Podocarpus macrophyllus blooms from early to mid-June and produces a great deal of pollen. Both A. eharai and T. vulgaris developed and oviposited well when they were reared on pollen of Podocarpus macrophyllus as food. Therefore, the increase of these phytoseiid species in June was thought to be due to the supply of pollen of Podocarpus macrophyllus as food.
