Flower injection of imidacloprid and spirotetramat: a novel tool for the management of banana thrips Thrips hawaiiensis

The banana thrips (Thrips hawaiiensis), which is one of the most common flower-inhabiting thrips, currently causes serious damage to banana trees in China. As spray treatments have low efficacy to control this thrips pest, changing to new control measures are crucial. Among the available approaches, injection of a systemic insecticide is considered suitable. However, little is known about this approach up to now. Between 2014 and 2018, imidacloprid and spirotetramat were applied via flower injection and evaluated for their potential to control the thrips. In 2014, laboratory bioassays together with field experiments revealed that imidacloprid and spirotetramat injected at recommended dose appeared to be effective in controlling the thrips, supporting the idea of flower injection. Thereafter, a 2-year study (2015-2016) of spirotetramat showed that higher injection rates resulted in greater mortality and better field efficacy against the thrips when flower injection was utilized. Another 2-year (2017-2018) field trial indicated that either imidacloprid or spirotetramat injection exhibited significantly higher efficacy and had no negative effects on fruit yield when compared to spinetoram spray. Results also showed that the efficacy of the flower injection was not influenced by banana species and phenological conditions. Moreover, the fast uptake of imidacloprid and spirotetramat in flower samples could account for their lethal activity against the thrips in bioassays. Notably, these two products degraded quickly in the young fruit and no residue was detected within the ripe fruit, implying that the flower injection might not present a risk to contaminate fruit. Overall, these findings taken together represent for the first time that flower injection of imidacloprid and spirotetramat can be regarded as a new alternative to control the banana thrips effectively.