Effects of foliar apple trichomes on G alendromus occidentalis ( N esbitt) ( A cari: P hytoseiidae): preferences, fecundity and prey consumption

Tritrophic interactions may alter the efficacy of biocontrol agents such as G alendromus occidentalis , the primary predator of tetranychids in W ashington S tate apple. Apple cultivars vary in leaf pubescence, which may differentially affect the performance of G . occidentalis . The present study aimed to determine both preference and performance of G . occidentalis on pubescent and glabrous surfaces. Choice tests were conducted on two apple cultivars: ‘ O regon S pur D elicious’ – pubescent and ‘ G olden D elicious’ – glabrous, as well as by adding simulated trichomes to a bean leaf disk. No‐choice tests measured oviposition and prey consumption on the two apple cultivars. G alendromus occidentalis consumed more prey on the ‘ O regon S pur D elicious’ side of arenas, although only when arenas were constructed without including the leaf midrib. When the midrib was included, G . occidentalis preferred to oviposit on the ‘ O regon S pur D elicious’ side. The preference of G . occidentalis for simulated trichomes did not lead to a performance difference between cultivars. In the no‐choice test, G . occidentalis did not differ in performance between cultivars. These studies indicate that G . occidentalis may have a slight preference for more pubescent surfaces, although this preference is not sufficiently strong to alter its biocontrol performance. As a specialist, G . occidentalis may be more adapted to tracking populations of its prey than locating ‘ideal’ host plants.