Effects of Two Buckwheat Varieties on the Behavioral Choice of Frankliniella intonsa in Sunflower Field

Damage caused by Frankliniella intonsa to sunflower seeds results in the emergence of rusty speckling on the seedcoat, severely compromising seed quality in recent years. Although chemical control has remained the primary management strategy, its application during the flowering period—when F. intonsa is the most active—poses significant risks to pollinating insects and natural enemies, highlighting the urgent need for effective and environmentally sustainable control alternatives. Previous studies have shown that F. intonsa is attracted by buckwheat and that it could be a promising trap crop for F. intonsa. Thus, the attractiveness of Fagopyrum esculentum and F. tataricum to F. intonsa was compared, and the preference of F. intonsa between two buckwheat varieties was examined. Furthermore, the behavioral responses of F. intonsa to volatiles emitted by these plants in different developmental stages were assessed. The study results indicated that F. intonsa had a clear preference for F. tataricum over F. esculentum. In cage trials, the selection rates of 2nd instar nymphs and adults of F. intonsa for F. tataricum were 61.63% and 60.19% at the seedling stage, and 60.74% and 62.50% at the full-bloom stage, all significantly surpassing those of F. esculentum. Olfactory bioassays further confirmed that flowers of F. tataricum were notably more appealing to both 2nd instar nymphs and adults of F. intonsa, with selection rates of 64.17% and 61.67%, respectively. Twenty distinct floral volatiles of two buckwheat varieties were detected through the phytochemical analysis. Orthogonal partial least squares-discriminant analysis (OPLS-DA) identified seven key compounds that accounted for the observed behavioral differences. Both 2nd instar nymphs and adults of F. intonsa demonstrated a significant selection for Δ-Cadinene, with the highest selection rates of 75.00% and 76.67% recorded at a concentration of 0.1 μg/μL. Furthermore, F. intonsa exhibited a marked attraction to higher concentrations of Verbenone, which was unique to F. tataricum, and (S)-2-Methyl-1-butanol, which was unique to F. esculentum. Field intercropping experiments confirmed that F. tataricum outperformed F. esculentum in trapping F. intonsa within sunflower plots. In conclusion, the results indicated that F. tataricum possessed considerable potential as a trap crop for the integrated management of F. intonsa in sunflower cultivation systems.