On Guam, mango trees are damaged by mango shoot caterpillar,Penicillaria jocosatrixGuenée. Growth variables were measured on trees defoliated by the caterpillar, and on trees that were protected by application of carbaryl. Mango shoot caterpillars removed 54% of the foliage of untreated trees compared with 10% in treated trees. Treated trees produced new foliage about twice during the year, whereas damaged trees flushed four times. Shoots on damaged trees were shorter and initiated fewer leaves, but the size of the leaves was not affected. There was a significant negative association between severity of damage to a shoot and interval until new shoot initiation. Shoots that flushed out of synchrony with the majority suffered heavier caterpillar damage. Untreated trees compensated for damage by producing additional flushes, but at the end of one year they still had one-third less foliage than treated trees. At the end of one year, trees that had a leaf area<4–5 m2per 25 shoots did not flower in response to an inducer.