Thursday, February 25, 2010
Monday, February 15, 2010
Note also the comment below from a study by Jason Williams at Miami University (my italics):
It would seem quite possible then, that anything that induced a larva to slip prematurely out of the dormant state (perhaps unseasonable weather, or unfortunate microclimate effects) would increase its susceptibility to dessication.
Some related studies have also shown that temperature-stressed ova give rise to larvae which are less tolerant of extreme climatic conditions. Again, not specifically in iris but it would seem a reasonable hypothesis.
In response to MO's interesting report, dessication certainly seems to be a problem with iris larvae during certain winters, certainly in captivity, and it would appear in the wild also. I imagine that the problem is complex; could this possibly linked to the significant desiccating effects of repeated frosts as well as a other factors affecting microclimate? Conversely in mild damp winters mould is also a significant threat to the over wintering larvae, although this phenomena may be greatly exaggerated in captivity due to the limited air circulation in a netting sleeve.
Camilla also suffers significant losses due to apparent dessication (larvae shrivel and harden) during some winters, both in the wild and in captivity, almost always towards the end of the winter, approaching the time at which one would be expecting to see the larvae preparing to become active again. I wonder if the larval mortality rate in iris during this phase is the factor that has the most influence upon whether or not we have a 'great' iris year...
Matthew's study is certainly raising some interesting questions.