Tiny White Specks: Lachnellula resinaria var. resinaria

Lachnellula resinaria var. resinaria

So this one was just a fluke, really, or maybe desperation on my part at the end of a slow day slogging through the snow and finding nothing new. Whatever it was, on my way home I beaned in on a clutch of tiny white specks on the trunk of a big standing dead spruce at about eye level. I didn't have my loupe with me, so close-up all I could see were tiny blurry white specks. But, what the hey, on the off chance they were something more interesting than ice crystals or bits of mold, I got out my knife.

The second time I found Lachnellula resinaria var.
resinaria it was growing on balsam fir resin.

Though I'd anticipated having to struggle through at least a hundred years of bark with my blade, the white dots were actually attached to a chunk of crumby resin, which easily dropped into my hand. I blew on the white dots with my warm breath. They didn't melt, so I wrapped them up and put them in my bag.







At home I inspected them with the loupe—as I expected, just fuzzy specks of mould. But wait a minute—why did two of those specks seem to have slits in the middle? And could that be a dot of egg-yolk yellow in the middle of another? I should probably mention that the biggest of these "specks" was less than a millimetre in diameter.

Even rejuvenated, the largest was barely a millimetre in diameter.

I submerged them in warm water and half an hour later I was looking at a clutch of tiny perfect Lachnellula that had opened up like flowers, sunshine-y yellow disks trimmed with white "fur." Cute as a button. 

These Lachnellula quickly revived in warm
water and then produced spores. 

I offered these tiny ascomycetes a slide to drop spores on overnight and they kindly obliged, which made the task of identifying them to species easier than it might have been otherwise. Their spores were very small (2.75-4.25 x 1.5-2.4 µm) and ellipsoid-fusoid, which made them Lachnellula resinaria var. resinaria. The only other species with such tiny ascospores, along with white hairs, is the closely related Lachnellula resinaria var. calycina, but its spores are more globose.

Lachnellula resinaria var. resinaria ascospores

Though Lachnellula resinaria var. resinaria, like most Lachnellula species, is usually saprobic, it might occasionally also be mildly pathogenic. Only Lachnellula willkommii is problematic as a pathogen. Introduced to North America in 1904, it causes "European larch canker," which can spread easily from branch to branch, particularly where conditions are moist. 

Like L. willkommii, Lachnellula resinaria var. resinaria can also be found on Larix, as well as on Abies (see photo above) and Pinus, but it's preferred host is Picea, where I first found it. Though it can sometimes grow on dead twigs or bark, it appears most frequently on blackened, resinous canker wounds. 

There's not a lot of information about Lachnellula resinaria var. resinaria in North American on the internet. I'm not sure if this is because it's rare, or just rarely collected. Because of its diminutive size, I suspect it's the latter reason. 

References:

H.O. Baral's Worldwide Key to Lachnellula (pdf)

USDA Lachnellula willkommii Fact Sheet

See also my post on Lachnellula subtilissima