The relationship between budburst phenology and damage by the pear thrips (Taeniothripsinconsequens (Uzel) (Thysanoptera: Thripidae)) to sugar maple (Acersaccharum Marsh.) foliage was investigated in two studies. In the first study, seedlings in cages were exposed to adult thrips at different stages of budburst. Compared with uninfested control seedlings, introduction of five adult thrips per bud reduced total leaf area and average leaf size, and caused chlorosis, tattering, and cupping of leaves. Leaf area reduction and damage symptoms were greater for seedlings exposed to thrips when leaf margins were first visible at the tip of the bud compared with earlier and later stages of budburst. In the second study, budburst date and number of thrips oviposition sites on leaves (an index of thrips activity) were measured in a common-garden test of maple saplings from open-pollinated families. Thrips activity was greater on early-breaking than late-breaking buds. Date of opening for these early-breaking buds coincided closely with peak capture of flying thrips. Both budburst date and number of oviposition sites on leaves differed among families. Sugar maple genotypes with late budburst escaped heavy thrips damage. The results indicate that timing of vegetative budburst in sugar maple can influence the degree of thrips damage.