Thrips Spatio-Temporal Distribution in Cowpea (Vigna unguiculata (L.) Walp.) Flowers Based on the Flower Structures...

Megalurothrips usitatus (Bagrall 1913) (MTU) is a major pest of cowpea (Vigna unguiculata (L.) Walp.) and shows a strong preference for floral tissues. To clarify the spatiotemporal distribution of thrips, we conducted a detailed survey of their abundance in flowers of different developmental stages-sampled in the morning (preanthesis flowers, PAF; open flowers, OPF; postanthesis flowers, PoAF) and at dusk (preanthesis flowers scheduled to open the next morning, PAF-D; closed flowers, CF). Behavioral responses of MTU to floral volatiles from these stages were evaluated using a Y-tube olfactometer, followed by chemical analysis via gas chromatography-mass spectrometry (GC-MS). The results indicate that 58.3% of adults sheltered in keel petals, while 76.7% of nymphs aggregated inside the diadelphous stamens. Thrips abundance on OPF in the morning was significantly higher than on PAF or PoAF, but did not differ significantly from that on CF. Olfactometric assays demonstrated a clear preference of MTU for OPF, which emitted a greater number and higher concentrations of volatile compounds compared to PAF, PAF-D, CF, and PoAF. Together, these findings reveal distinct spatiotemporal dynamics of thrips in relation to cowpea flower development, underscoring the role of floral age in driving host-switching behavior.