Cold acclimation increases Asian citrus psyllid (Diaphorina citri Kuwayama (Hemiptera: Liviidae) survival during exposure to freezing temperatures

Authors: Stockton, Dara; MARTINI, XAVIER - University Of Florida; MALFA, KATHI - University Of Florida; RIVERA, MONIQUE - University Of California (UCLA)

Submitted to: Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2021
Publication Date: 7/13/2021
Citation: Stockton, D.G., Martini, X., Malfa, K., Rivera, M. 2021. Cold acclimation increases Asian citrus psyllid (Diaphorina citri Kuwayama (Hemiptera: Liviidae) survival during exposure to freezing temperatures. Insect Science. 0:1-8. https://doi.org/10.1111/1744-7917.12936.
DOI: https://doi.org/10.1111/1744-7917.12936

Interpretive Summary: Cold acclimation in the Asian citrus psyllid appears to enhance cold tolerance. The following study used gradual cooling to acclimate these invasive insects in the lab then studied how they responded to cold shock below freezing. Once acclimated, survival exceeded 80% compared to 20% in the non-acclimated group. However, intermittent acclimation, which in some insects appears to be beneficial by allowing insects to recover following cold stress, did not improve upon this cold tolerance and may have been detrimental. These data suggest gradual cold acclimation may confer sufficient cold tolerance to allow survival during brief freezes, as occur along the northern boundary of citrus production in the United States.

Technical Abstract: Asian citrus psyllid Diaphorina citri is the vector of the pathogenic bacteria causing citrus greening, the most devasting disease affecting citrus worldwide. While mortality of Asian citrus psyllid has been studied widely, much less is known regarding the extent to which this sub-tropical species may display resistance to freezing temperatures and the acclimation potential of psyllid to cold. We first evaluated cold resistance of Asian citrus psyllid depending of color morph and sex to determine if these factors should be addressed separately. Subsequently, we compared acute mortality of when exposed to a cold stress temperature of -4 °C for 10h. We compared survival among 3 treatments: between unacclimated psyllids, psyllids gradually cold acclimated during one or two weeks. In our final experiment we studied the effects of intermittent acclimation, also for one or two weeks. We did not find major difference in cold resistance between color morph and psyllid sex. We found that after 1 week of gradual acclimation, the survival of psyllids at -4 °C increased to > 80%, compared to 20% in the control group. Survival did not increase more after a second week of gradual acclimation. Although intermittent acclimation improved survival compare to the control group, it was less effective than constant acclimation with a survival at 30% and 70% after 1 and 2 weeks of acclimation, respectively, although this difference was not significant at week 2. These data show that gradual cold acclimation allows D. citri to survive brief periods below freezing. This may serve as a mechanism responsible for increasing northern establishment of this pest.