Diversity and Seasonal Abundance of Predacious Mites in Alabama Satsuma Citrus

Abstract Nine Satsuma citrus orchards (seven conventionally sprayed and two unsprayed) in southern Alabama were sampled (mainly leaf samples) for predacious mites at eight different sampling dates from March 2005 to February 2006. At least 29 species of predacious mites from nine families (Anystidae, Ascidae, Bdellidae, Cheyletidae, Cunaxidae, Erythraeidae, Eupalopsellidae, Phytoseiidae, and Stigmaeidae) were identified. In addition, six primarily fungivorous species from three families (Parasitidae, Tydeidae, and Tarsonemidae) were recorded. Predacious mites in the families Phytoseiidae (18 species) and Stigmaeidae (one species) were the most abundant. The dominant species were Typhlodromalus peregrinus (Muma) and Proprioseiopsis mexicanus (Garman) (Phytoseiidae), and Agistemus floridanus Gonzalez (Stigmaeidae). Phytoseiid mites were most abundant in the spring with populations declining at the start of the summer and remaining at very low levels through the fall and winter. Analysis of fruit, leaf and orchard ground cover plant samples collected in fall (October) 2005 showed greater abundance of phytoseiid mites on ground cover plants than on citrus fruit and leaves, suggesting that ground cover plants may serve as overwintering reservoirs for predacious mites. In general, predacious mites were relatively more abundant in the conventionally sprayed orchards compared with the unsprayed orchards, as were the two key phytophagous species, Panonychus citri (McGregor) and Phyllocoptruta oleivora (Ashmead). The results are discussed in relation to the potential of the dominant predacious mite species as candidates for biological control of key phytophagous mites on Alabama Satsuma citrus.