Researchers monitored the population dynamics of four insect defoliators in a 5-year-old Eucalyptus bosistoana plantation in New Zealand over a 5-month period. They found that two moth species exhibited two generations, while a sawfly and beetle species had overlapping generations with larval peaks in different months. Temperature strongly correlated with abundance of one species. Observation of only one generation of one species was likely due to dry conditions during the study period. Results provide information for predicting and managing future outbreaks of insect pests in E. bosistoana plantations.