Species distribution models predicting climate suitability for the psyllid Trioza erytreae, vector of citrus greening disease

Abstract

The African citrus psyllid, Trioza erytreae (Hemiptera: Triozidae), is a vector of citrus greening (Huanglonbing - HLB), a bacterial citrus disease caused by Candidatus liberibacter spp. Native to Africa, T. erytreae was detected in the Canary Islands and Madeira in the early 2000s and then in northwestern Spain in 2014. Since then, T. erytreae has become established along the Atlantic coastal areas of the Iberian Peninsula. Therefore, an accurate assessment of the potential long-term establishment of T. erytreae in major citrus-growing regions of Europe and the world is urgently needed to design adapted control strategies. I calibrated correlative species distribution models to understand the bioclimatic characteristics that determine the distribution of T. erytreae, and to assess the climatic suitability of the world's major citrus-growing regions for the psyllid under current and future climate conditions. I calibrated the models using only distribution data from Africa (its native range), the Canary Islands, and Madeira, and evaluated them using available data from the invaded area in continental Europe. This approach aims to avoid spurious good measures of model accuracy arising from spatial autocorrelation between the calibration and evaluation datasets. The models identify mild summer and winter temperatures and high levels of precipitation as optimal conditions for long-term psyllid establishment, consistent with its physiology. In Europe, models predict only the Atlantic coastal regions of the Iberian Peninsula as highly climatically suitable, a spatial pattern that corresponds exactly to the area currently invaded by the psyllid. Models predict that most of the important citrus-growing areas in the world are, and will remain in the future, poorly adapted to T. erytreae except in case of future physiological adjustments. These results are crucial for the design of appropriate pest management strategies and are timely for Europe where the African citrus psyllid has recently been detected.