Thrips (Thysanoptera) damage to apples and nectarines in Western Australia

Thrips (Thysanoptera: Thripidae) are economic pests of deciduous fruit tree crops, causing direct damage during fruit development and as fruits mature. Blue wet sticky traps, direct sampling of trees (foliage, flowers, fruit), thrips exclusion experiments and weed sampling was carried out from 2007 to 2009 in nectarine and apple orchards, to determine which thrips species were present, when they occurred, what type of damage they caused and whether they occurred on orchard weeds. The native plague thrips (Thrips imaginis Bagnall) was the dominant species in all orchards from budburst, and the most abundant and widespread species during flowering in nectarines. Western flower thrips (Frankliniella occidentalis (Pergande)) and onion thrips (Thrips tabaci (Lindeman)) were first detected at budburst in nectarines and apples, although they were not widespread and abundant until fruit development. Silvering was the most common type of thrips damage, primarily associated with F. occidentalis, though adult tomato thrips (Frankliniella schultzei (Trybom)), T. imaginis, T. tabaci were also collected from silvered fruit. Both T. imaginis and F. occidentalis caused scarring in nectarines, but only F. occidentalis caused pansy spot damage to apples in exclusion experiments. Frankliniella schutzei and T. tabaci are regarded to be minor pests. Wireweed (Polygonum aviculare L., Plantaginaceae) and plantain (Plantago lanceolata L., Plantaginaceae) may be important summer hosts for adult F. occidentalis within the orchard, and temperature extremes may be limiting F. occidentalis populations.