In the second edition of our blog series “Plant research glimpse”, we focus on a new paper published in the Biological Control journal by VIRTIGATION partners LIST and UNICT. Their study assesses the longevity of the key whitefly biocontrol agent Encarsia formosa, a parasitoid, under projected future climate change conditions.
Biocontrol of whiteflies through parasitoids
Whiteflies have wreaked havoc on horticultural crops grown in greenhouses. By feeding on the phloem of plants, whiteflies like the Bemisia tabaci or Trialeurodes vaporarium cause stunted growth, chlorosis and wilting. These whiteflies also transmit devastating plant viruses as e.g. ToLCNDV and TYLCV. To mitigate the damage caused by whiteflies, biocontrol through natural whitefly enemies such as parasitoids has become common practice in the value chain. The most important whitefly parasitoids are wasps from the genera Encarsia and Eretmocerus, with one of the most used parasitoid species being the Encarsia formosa.
Climate conditions as key factor in biocontrol systems
According to the LIST and UNICT scientists, the ongoing anthropogenic climate change could seriously disrupt the effectiveness of current biocontrol systems. The key whitefly parasitoid Encarsia formosa is no exception to this anticipated disruption. However, value chain actors lack precise information about the impact of projected future climate conditions on the fitness of the Encarsia formosa. This is crucial however, as a foreseen hotter climate is expected to enable whiteflies to overwinter ever further north than is currently the case. Against this potential threat, it is vital to understand if parasitoids like the Encarsia formosa can still perform their role as biocontrol agent vis-à-vis whiteflies.
In their paper, the LIST and UNICT researchers evaluated the parasitization rate, development time, and longevity of the key whitefly parasitoid Encarsia formosa, by performing climatic chamber simulation driven by physically consistent, regionally downscaled, numerical future climate projections. Through their study, the VIRTIGATION entomologists assessed how well the Encarsia formosa would perform under projected future climate conditions compared to present ones.
Encarsia formosa perform better, but live for a shorter time under future climate conditions
Through their publication, the LIST and UNICT entomologists show that under projected future climate conditions, Encarsia formosa is set to enhance its performance as a whitefly biocontrol agent, but have its lifetime reduced significantly. Their results show that Encarsia formosa’ development time is expected to be reduced by 8.6 days, while their parasitization rate would increase 15-fold. However, the longevity of the whitefly parasitoid is foreseen to be reduced by 38%. While the climate of Luxembourg was taken as focal point for this study, the LIST and UNICT researchers note that it would be likely the same in other Central European climates.
As with their recent paper on another important whitefly biocontrol agent, the Eretmocerus eremicus, the findings of LIST and UNICT show that future climate conditions will negatively affect the lifespan of the Encarsia formosa. Whether the projected increase in Encarsia formosa fitness (i.e. shorter development time and higher parasitization rate) will be still sufficient in counteracting the foreseen faster whitefly development, is a question that the LIST and UNICT study cannot conclusively answer yet. The LIST and UNICT authors state that more frequent releases of this key whitefly parasitoid would likely be necessary, thus increasing biocontrol cost for the tomato and cucurbit value chain. While the LIST and UNICT paper lays the basis for filling a knowledge gap on assessing the effect of climate change on whitefly control methods, the authors conclude that further research is still needed to fully describe the efficacy of the Encarsia formosa in the future.
More info about LIST and UNICT's new whitefly study
The full version of LIST and UNICT’s study in the Phytoparasitica journal titled “Changes in longevity, parasitization rate and development time of the whitefly parasitoid Encarsia formosa under future climate conditions” is available online here since 20 September 2023. It has been authored by LIST’s principal investigators Matteo Ripamonti, Michael Eickermann and Jürgen Junk, as well as UNICT’s principal investigator Carmelo Rapisarda. The dataset underlying LIST and UNICT’s peer-reviewed, open access scientific publication is available in the VIRTIGATION Zenodo community. Find out more about VIRTIGATION’s scientific publications on our website here.