Spectral Preferences of <i>Encarsia formosa:</i> Unravelling Attraction to LED Monitoring Traps.

Abstract

LED-enhanced sticky traps improve monitoring of greenhouse whitefly, <i>Trialeurodes vaporariorum</i> Westwood (Hemiptera: Aleyrodidae), but their effects on its parasitoid, <i>Encarsia formosa</i> Gahan (Hymenoptera: Aphelinidae), are unclear, which may compromise biological control.<h4>Methods</h4>We quantified <i>E. formosa</i> visual responses in climate-chamber multiple-choice arenas using six LED colors at equal photon flux (8.1 μmol m^-2 s^-1) and in greenhouse choice/no-choice assays comparing a standard yellow sticky trap with a green LED-enhanced yellow trap, with and without host-infested tomato leaves. We further tested modified LED traps (green LEDs with white or green backgrounds) and assessed intensity-dependent responses (18.0-25.6 μmol m^-2 s^-1).<h4>Results</h4><i>E. formosa</i> showed the highest attraction to green LEDs (peak ≈ 521-524 nm) and a significantly lower response to other colors. In greenhouse assays, <i>E. formosa</i> preferred the standard yellow sticky trap over the LED-enhanced yellow trap; in no-choice tests, only 9% were recaptured on the LED-enhanced yellow trap, both without and with hosts. Modified traps with white or green backgrounds substantially increased <i>E. formosa</i> recapture (≈54% higher than the yellow-background LED trap). <i>Encarsia formosa</i> attraction to the white-background LED trap declined with increasing intensity (61% at 18.0 to 4% at 25.6 μmol m^-2 s^-1), whereas whitefly captures were stable to slightly higher.<h4>Conclusions</h4>The standard LED-enhanced yellow trap is compatible with <i>E. formosa</i> releases and does not disrupt biocontrol. Modified LED traps show promise for simultaneous monitoring of <i>E. formosa</i> and whiteflies, warranting validation under commercial conditions.