Neolema ogloblini: Exploring a new option for the control of tradescantia (Tradescantia fluminensis)

Abstract

The leaf beetle Neolema ogloblini was released in 2011 as a biological control agent for Tradescantia fluminensis, a major warm temperate forest environmental weed in New Zealand. To assess whether N. ogloblini can suppress T. fluminensis and improve native seedling growth and survival, a glasshouse experiment was established. Kawakawa (Macropiper excelsum) and mahoe (Melicytus ramiflorus) seedlings were planted underneath uncontrolled T. fluminensis and compared with seedlings (1) under T. fluminensis damaged by N. ogloblini, (2) under T. fluminensis sprayed with herbicide (triclopyr) and (3) released from competition by manually removing T. fluminensis. Seedlings did not grow faster in response to reduced T. fluminensis biomass and increased light levels following feeding by N. ogloblini over the 12-week experiment. However, seedling survival rates were higher (kawakawa 87% and mahoe 93%) with N. ogloblini feeding than herbicide-treatment (kawakawa 17% and mahoe 3%) T. fluminensis. Survival in uncontrolled T. fluminensis (kawakawa 90% and mahoe 57%) varied for the two species. This experiment suggests that regeneration of native plants may benefit from damage to T. fluminensis caused by N. ogloblini feeding in the field.