I have not seen a SHB infestation in winter either. It is my understanding that SHB can only survive in the cluster as Weil. But according to this report which study was conducted in South Korea, the finding show that the SHB not only survive in that hash environment, but can reproduce at cluster temp 68 f.
"In our previous study [24], we reported that SHB can continue reproduction at the temperature of winter bee's cluster (20 C), so feeding larvae still can be exposed to winter temperatures in the brood-less area or peripheral portion of the hives. "
I found this report to be worthy of at least bringing it to our members attention, for education or at least interesting discussion, thus the question/title of this thread; Because the SHB can reproduce at this temperature in the cluster according to the finding.
Now, I personally do not see how this finding can mean infestation, for one reason it has always been my understanding the SSHB larva need to burrow in the ground for pupation or transformation if you will.
Since the ground is Frozen in winter in the far North; and South Korea, that should stop this process thus the full reproduction cycle?
Or, Can the larva make the transformation inside the hive itself? Perhaps in the comb close to the cluster?
Phillip