Leaf Residency and Interleaf Movement of Four Phytoseiid Mites (Acari: Phytoseiidae) on Apple

Abstract

We studied the polyphagous predators, Typhlodromus pyri (Tp) Schunten and Amblyseius andersoni (Aa) Chant, to test if either had shorter residency times on leaves with abundant prey or had greater tendencies for interleaf movement than the oligophagous mites, Metaseiulus occidentalis (Mo) (Nesbitt) and Neoseiulus fallacis (Nf) (Garman), or if the opposite trends among species occurred when these mites were held without prey. Tests were nm on single apple, Malus pumila Miller, leaves or apple seedlings. Residencey times for immatures on leaves with no prey were much shorter for M. occidentalis , but with prey they were shorter for T. pyri and much shorter for A. andersoni . Residency times for female adults with no prey were similar among species, but with prey they were longest for M. occidentalis and shortest for A. andersoni . Patterns of interleaf movement of immatures were similar to residency data. On seedlings with abundant prey, larvae of all species moved little, but nymphs of A. andersoni and N. fallacis moved more than nymphs of T. pyri and M. occidentalis . Larvae of M. occidentalis held without prey moved most but its nymphs died and nymphs of T. pyri and N. fallacis moved more than nymphs of A. andersoni . Larvae with moderate levels of prey moved little but T. pyri nymphs moved less far than others. Immature losses were related to movement levels. Overall, data agreed with our hypotheses and helped explain why M. occidentalis and N. fallacis are better adapted to respond numerically to outbreaks of spider mites whereas A. andersoni and T. pyri are better adapted to keep them at low levels. Movement patterns are discussed in relation to competition and species displacement among these 4 mites.