The last week has seen some terribly cold weather in some of the citrus growing regions of California. Fortunately, it looks like we have escaped significant harm here at Petty Ranch, but the same cannot be said for many others.
It is against this backdrop that I came across this article in the Western Farm Press suggesting an upside to the freezing temperatures: Suppression of Asian Citrus Psyllid (ACP). In a nutshell, USDA study has found that psyllids are very susceptible to cold weather. Will this cold snap actually be a benefit to the citrus industry in the long run?
I place the greatest hope in the chance that a freeze will reduce ACP populations in urban and suburban areas where eradication efforts are no longer being made. Every psyllid eliminated from these areas is a psyllid that can’t be transported to a place where it can do more harm. These “islands” of psyllid populations feed the infestations and reinfestations that threaten orchards. Reducing them should tangibly slow the spread of the insect and the disease (Huanlongbing, or HLB)that it carries.
It may even be that cold is enough to completely eliminate ACP colonies, either directly or by destroying all the green shoots and young leaves that the psyllids and their nymphs feed on. Weather that clears an area of infestation might be worth some degree of damage.
But will taking a bite out of their numbers be enough? I sure hope so, but I have grounds for skepticism. Citrus trees recover from freeze damage quite slowly…it takes at least a couple of years to fully recover. Insect populations can grow very rapidly. A population of ACP that has been diminished but not destroyed by cold could easily return before an orchard is back in production. For obvious reasons, we can’t hope that regular freezes will provide relief. Recurring frosts every few years might keep the insect in check, but at a terrible cost to the citrus business.
So does this study simply provide false hope? I wouldn’t go that far. Suppressing urban populations of the pest is certainly a good thing. But in the world of production citrus, anything less than a “100% kill” is probably insufficient.