Seasonal abundance of insect biocontrol agents ofMimosa pigrain the Northern Territory

Nine insect species endemic to tropical America have been released into the Northern Territory as biological control agents for Mimosa pigra L. (Mimosaceae). To date, few studies have been published that quantify the abundance of these agents post‐release. Hence, populations of adult agents in three stands of M. pigra were monitored using Malaise traps. Trap catches frequently contained the lepidopteran agents Carmenta mimosa Eichlin and Passoa and Neurostrota gunniella (Busck). Neurostrota gunniella, which was first released in 1989, was the most abundant of all the agents caught, irrespective of the stand of M. pigra where trapping was conducted. The three coleopteran agents (namely Acanthoscelides Schonherr spp., Chlamisus mimosae Karren and Coelocephalapion Wagner spp.) were caught less frequently. Two recently released beetles, Chalcodermus serripes Fahraeus and Sibinia fastigiata Clark, were not caught. Trap catches of Acanthoscelides spp. were greatest during the late dry season with smaller catches during the mid‐ to late wet season. Chlamisus mimosae was most abundant during the dry to dry–wet transition. Neurostrota gunniella was generally most abundant during the dry season. The abundances of Ca. mimosa and Coelocephalapion spp. exhibited little seasonality. Malaise trapping is recommended as part of a long‐term monitoring program to quantify agent populations and their impact upon M. pigra.