The mite, the bug, and the nematode: Assessing the efficacy of three biological control agents against Echinothrips americanus (Thysanoptera: Thripidae)

The poinsettia thrips, Echinothrips americanus Morgan, 1313, is an invasive pest native to North America. The species attacks various protected ornamental and crop plants causing extensive foliage damage. Severe infestations have recently occurred in greenhouses specialized in Hibiscus spp. cultivation in Central Italy. Given the currently limited possibility for its integrated management, we evaluated the efficacy of three commercial biological control agents: the mite Neoseiulus californicus (McGregor, 1954), the bug Orius laevigatus (Fieber, 1860), and the nematode Steinernema feltiae (Filipjev, 1934). Our trials were conducted in Huffaker cages under laboratory conditions, using E. americanus second-instar larvae as prey/host. For the first two biological control agents, we assessed predation efficiency and predation latency times. For the nematode, we determined the parasitization efficacy and optimal treatment concentration. For N. californicus, we observed a predation rate of 50.52% after 48 h and predation activity beginning after a mean of 3 h and 53 min. Orius laevigatus provided a predation rate of 73.75% after 12 h and started preying after a mean time of 7 min and 31 s. The nematode, at the tested concentrations of 50, 100, and 150 infective juveniles cm􀀀 2 of leaf, showed a parasitization rate after 72 h of 46.59, 79.97, and 93.32%, respectively. In conclusion, O. laevigatus and S. feltiae are more effective as biological control agents against E. americanus. Given their different biology and behaviour, the integrated adoption of both agents for inundative release could be a valid solution for managing E. americanus in greenhouse hibiscus cultivation.