春まきタマネギにおける間作オオムギの播種時期がネギアザミウマ発生と収穫物に与える影響

抄録

In spring onion fields, barley intercropping is an effective control technique against onion thrips. Nevertheless, barley intercropping might result in smaller onion bulbs than those without barley intercropping. To mitigate this adverse effect on onion bulbs, we investigated barley sowing timing and their suppression effects against onion thrips population. This experiment included three treatment plots, viz., barley sowing at the same time of onion transplanting (0-week plots), 2 weeks after transplanting (2-week plots), and 4 weeks after transplanting (4-week plots). Although sowing at 2- and 4-week plots significantly reduced the adverse effects on onion bulbs compared with sowing at 0-week plots, the suppression of onion thrips was significantly less effective in 4-week plots compared with that in other plots. Therefore, barley should be sown between 2 weeks after onion transplanting and the first observation of onion thrips to mitigate the adverse effects on onion bulbs and achieve effective control of onion thrips.