Abstract. 1. The slow-growth, high-mortality hypothesis was experimentally tested in this study by investigating the effects of plant quality and natural enemies on leaf-miner growth, performance, and survivorship. Two leaf miners (Acrocercops albinatella and Brachys tesselatus) occurring on the turkey oak Quercus laevis were studied using a factorial design that manipulated predation/parasitism pressure and plant nutritional quality.
2. Forty trees were randomly divided into four treatments: (1) control plants (nutrients and natural enemies unaltered); (2) nutrients added, natural enemies unaltered; (3) nutrients unaltered, natural enemies reduced; and (4) nutrients added and natural enemies reduced. Water content, leaf toughness, tannin concentration, and foliar nitrogen were quantified monthly for each plant, and mine growth and survivorship were assessed by tracing mines on a 2–3-day interval and by following the fates of 50 mines per species per treatment combination.
3. Fertilised plants exhibited significantly higher amounts of nitrogen, but no significant differences among treatments were observed for water content, leaf toughness, and tannin concentration. These results only partially support the slow-growth, high-mortality hypothesis, as mines were significantly smaller and developed faster on fertilised plants, but neither fertilisation nor natural enemy exclusion significantly affected mine survivorship or mortality caused by natural enemies.