Volatiles from non-host plant <i>Baccaurea ramiflora</i> (Malpighiales: Phyllanthaceae) attract cowpea thrips, <i>Megalurothrips usitatus</i> (Thysanoptera: Thripidae)

The cowpea thrips Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae) exhibited unexpected aggregation on flowers of the non-host Baccaurea ramiflora Lour. (Malpighiales: Phyllanthaceae), suggesting floral volatile-mediated attraction. We systematically investigated this phenomenon through: (i) GC-MS identification of B. ramiflora floral volatiles; (ii) electroantennographic (EAG) and olfactory assays; and (iii) field trapping experiments. Both the flowers of B. ramiflora and their headspace extracts exhibited significant attractive effects on M. usitatus. Five key volatile organic compounds were consistently detected: linalool, 2,4-decadienal, trans-2-decenal, (Z)-β-ocimene, and trans-2-undecenal. The antennae of M. usitatus demonstrate distinct sensitivities to different volatiles, with the appearance of their EAG response peaks being affected by the dosage levels at which these volatiles are applied. The olfactory responses revealed that linalool (100 to 10000 μg), 2,4-decadienal (10 to 10000 μg), and trans-2-undecenal (1000 to 10000 μg) attracted M. usitatus. Trans-2-decenal attracted M. usitatus at 1000 μg but repelled at 10000 μg. (Z)-β-ocimene repelled M. usitatus at doses ranging from 10 to 10000 μg. Field trials confirmed 2,4-decadienal (10 to 100 μg) as the most effective attractant. These findings support the development of a 2,4-decadienal-based semiochemical strategy for sustainable M. usitatus management in cowpea production systems.