Occurrence of Scirtothrips dorsalis and insecticide spraying reduced program using reflective sheet mulching in grapevine 'Shine Muscat'

Occurrence of yellow tea thrips (YTT), Scirtothrips dorsalis and insecticide spraying reduced program using reflective sheet (RS) mulching were investigated in hedgerow grapevine cultivar 'Shine Muscat' (Vitis labruscana Bailey * V. vinifera L.). 1. First catches of YTT adults on yellow sticky traps in grape orchards were observed in mid- to late May or mid-June. Trap catches of YTT tended to be decreased by RS mulching. First infestation of YTT adults on grape shoots was observed in late May or mid-June. Infestation of YTT adults on shoots tended to be delayed by about 2 to 4 weeks by RS mulching, and the number of YTT infesting grapevine shoots tended to decrease with RS mulching. 2. The overwintering generation of YTT adults was collected from Distylium racemosum, Hydrangea macrophylla, Viburnum odoratissimum, and two species of weeds, Lamium amplexicaule and Vicia sativa subsp. nigra. First-generation of YTT adults were collected from Podocarpus macrophyllus and Camellia sinensis. It is likely that first- and second-generation of YTT adults grown on these host plants flew to grapevines. 3. Estimated immigration peaks of the first-, second- and third generation of YTT adults coincided with the peaks of trap catches of the first- and second-generations and the period of the number of YTT adults increasing on grapevine shoots in July, respectively. 4. Fruit damage in grapevines not sprayed with insecticide and without mulching (unsprayed), those receiving conventional insecticide spraying without mulching (conventional), and those with reduced insecticide spraying with RS mulching (mulching) were compared. Infestation of YTT adults on unsprayed grapevine shoots was observed in late May and late June, and fruit damage was observed in this block. Infestation of YTT adults on grapevine shoots in the conventional and mulching treatments was not observed by the bagging day, and no fruit damage was observed in these blocks. 5. Insecticide spraying timed during immigration of the first-generation of YTT adults was considered to be unnecessary if RS mulching was used. However, because second-generation YTT adults were observed on shoot tips of grapevine with RS mulching, insecticide spraying timed during adult immigration in this generation was considered to be necessary.