The effects of LED daylength extensions on the fecundity of the pest aphidMyzus persicaeand the daily activity patterns of its parasitoid,Aphidius matricariae

Abstract

Supplemental lighting, such as with LED lamps, allows greenhouse producers to maintain yields when natural light levels are low. Since both insect pests and their natural enemies are sensitive to light, both the duration and spectrum of LED daylength extensions could affect biological pest control in greenhouses. Longer days could allow for extended periods of reproduction for pests or foraging activity of biological control agents, possibly depending on the spectra used for these extensions. However, the effects of lengthening days with different LED spectra on the behaviour of biological control agents has mostly been studied in short-term experiments to date, and has not always included the context of the light's effect on their hosts' reproduction. In growth chambers, we examined the locomotor activity of the parasitoid biocontrol agent Aphidius matricariae (Hymenoptera : Braconidae) as a predictor for foraging activity and the fecundity of its aphid host Myzus persicae (Hemiptera : Aphididae) over multiple days under different daylength extension regimes representative of those used in greenhouse vegetable production. We compared the effects of 14, 16, 18, and 20 h photoperiods, and 12 h days extended by 6 h with three different spectral qualities. The parasitoids adjusted how their activity was distributed throughout the lit period of the day (i.e., its total duration and peak timing) without changing the total amount of daily activity, regardless of the photoperiod or the light spectrum used for daylength extension. The aphids' peak fecundity was not affected by photoperiod or spectral quality. Our results suggest that at least some behavioral and reproductive traits of these insects can be resilient to even drastic changes in their light environment.

Supplemental LED lighting improves plant growth without affecting biological control in a tri-trophic greenhouse system

“…persicae's fecundity. This reinforces our findings (Fraser et al, 2023) that greenhouse LED lighting is not likely to substantially affect the growth of aphid populations once the aphids have settled on a host plant, even in cases where the plants are strongly affected.…”

“…Here, we specifically asked how pest suppression (and resultant plant protection) by a biological control agent might be affected by LED lighting, which is increasingly being used in greenhouse production. While photoperiod and spectral quality have previously been shown to affect insect parasitoid behaviour (Cochard et al, 2017(Cochard et al, , 2019Fraser et al, 2023;Kehoe et al, 2020;Zilahi-Balogh et al, 2006), it was not known how this translated to impacts on biological control efficacy (i.e.…”

“…The same was true for differences in natural light levels among the temporal blocks. We established in previous research (Fraser et al, 2023) that lighting conditions very similar to these LED treatments did not produce significant effects on M.…”

“…Previously, we showed that A. matricariae adjusted its activity timing and intensity in response to the light environment, while keeping total activity levels constant, and showed the most intense activity under light with the highest proportion of short to midlength wavelengths (i.e. below 600 nm) (Fraser et al, 2023). This is consistent with the fact that most insects-including aphids and most Hymenoptera-have photoreceptors with peak sensitivity to UV, blue, and green light, and would not be expected to see red very well, or far-red at all (Briscoe & Chittka, 2001;Kirchner et al, 2005;Peitsch et al, 1992).…”

“…(2) Illumination might have subtle direct effects on aphid fecundity (Joschinski et al, 2015). (3) Choice of lighting may influence parasitoid activity (Cochard et al, 2017;Fraser, 2022;Fraser et al, 2023) and parasitism rates (Cochard et al, 2019;Kehoe et al, 2020). (4) Phloem-feeding insects, like aphids, may benefit from improved plant growth (Cornelissen et al, 2008).…”