For a number of years now scientists have been studying why plants are able to effectively fight many common viruses in hot climates but are less effective in cool climates. The explanation (proposed in 2003 by György Szittya, Dániel Silhavy, Attila Molnár, Zoltán Havelda, ÃÂgnes Lovas, Lóránt Lakatos, Zsófia Bánfalvi, and József Burgyán, EMBO J. Feb 3, 2003; 22(3): 633��"640, ) centers about the siRNA-mediated RNA silencing being a temperature dependent pathway. At first this was thought to occur only in plants, but now is considered to be a possible pathway in all virus infected forms of life (plant, animal, insect, bacteria, etc.).

I thought that since mosquito season is upon many of us, that this recent study would be of interest to many rose growers:
Title: "Cooler Temperatures Destabilize RNA Interference and Increase Susceptibility of Disease Vector Mosquitoes to Viral Infection"

" Author Summary
Although a link between the increased susceptibility of mosquitoes for arthropod-borne viruses and exposure to lower rearing temperatures has been known for many years, the molecular basis of this has remained unknown."
..........................................."Specifically, we demonstrate that RNAi, a critical antiviral immune pathway in mosquito vectors of human disease, is impaired in insects reared at cooler temperatures."

http://www.plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.pntd.0002239

Here is a link that might be useful: link to mosquito - virus study