RESPONSE OF PINOT-NOIR GRAPEVINE GROWTH, YIELD, AND FRUIT COMPOSITIONTO DEFOLIATION THE PREVIOUS GROWING-SEASON

Leaf removal has been increasingly employed to improve the cluster mic roclimate. Leaf loss has been suggested to reduce fruitfulness and har diness of buds at that node. Before such a practice can be accepted in temperate zone climates, the impact on such bud and subsequent growth factors requires critical evaluation. Leaf removal at a point about h alf way between fruit-set and veraison (berry pea-size or 7 mm diamete r) during Year 1 (1989) had minimal impact on main and lateral leaf nu mber or area, vine yield or yield components, or fruit composition val ues in Year 2 (1990). No defoliation occurred in 1990. One notable exc eption was the increase in percentage of shootless nodes at positions where leaves had been removed. Node position influenced bud fruitfulne ss (nodes 1 and 2 had lowest yields) and node 4 (where the basal clust er was commonly produced) consistently was less fruitful than node 3, 5, or 6). It was also significantly more frequently shootless. Further experimentation should be undertaken to assess the impact of leaf rem oval on bud and cane cold hardiness and fruitfulness suggested by thes e data in climates where such damage is a persistent viticultural conc ern.