Black spots on Tulip Poplar

[TSAW]

Hey all, it seems no matter what I do every time I cut some tulip poplar boards or even the end of the logs I get small black spots that I assume is mold.  Is there a good way to deal with this wood to avoid those spots or just leave it and plane it down later?

[Don P]

Hey all, it seems no matter what I do every time I cut some tulip poplar boards or even the end of the logs I get small black spots that I assume is mold.  

If it is happening in winter it isn't mold.
If it is mold the controls are, temperature (cold), moisture (dry), oxygen, (pond it), food (poison it)
Of those it is usually easiest to dry it faster. With poplar I have to borate it to keep the critters down to a dull roar.

[TSAW]

I will try to get some pictures and post later today.  It seems to happen with fresh stuff even after trying to get all the dust off and occurs within a few days to a week, stacked and stickered appropriately with tin over the stack.

[TSAW]

@Don P When you say you use borate, is that to prevent mold growth or for bugs?

[Don P]

I do it for bugs it will mildly slow mold. I'm trying to figure out if yours is a mold problem but you didn't answer, does it happen in winter? if so it isn't mold. If it is mold airflow will be the most helpful.

[Ron Wenrich]

The black spots in the sapwood of tulip poplar is blue stain.  It just turns black in tulip poplar.  You shouldn't be getting it in the heartwood, if it is stain.  There are also black streaks in poplar that are caused by the Columbian beetle.

You can spray your lumber with Sta-Brite that will help prevent the blue stain.  We used it on poplar that was being sent to customers that were going to sticker and kiln it.  It gave us a chance to get a load up and shipped without staining.  Stained tulip poplar gets dropped to a 2Com or less.

Here's a discussion we had 20 yrs ago on the subject:

https://forestryforum.com/board/index.php?topic=2581.0

[TSAW]

I do it for bugs it will mildly slow mold. I'm trying to figure out if yours is a mold problem but you didn't answer, does it happen in winter? if so it isn't mold. If it is mold airflow will be the most helpful.

Sorry, I jumped ahead and missed that part about winter.  It is all from stuff milled in the last few months so lowest temps in the 50's up to high 70's here.  

[Don P]

I try to put it in a place where wind will go through it and like I said we have to borate to keep the bugs out but the wood generally dries bright. Maybe try to improve airflow first then bring in the chemicals if it still isn't working. We are heading into the worst blue season now though, high temp and humidity.

Bummer, looking at that old thread Dr Wheeler must have retired at State and they took her slides and syllabus down.

[Don P]

While wandering around looking for pics this popped up.
Identification and Evaluation of Strain B37 of Bacillus subtilis Antagonistic to Sapstain Fungi on Poplar Wood (hindawi.com)
 Pretty deep in the weeds and I was skipping over the tops. The poplar they are discussing is populus but the sapstain is the same. They were experimenting with bacteria that would inhibit the sapstain fungi, and were successful. Hopefully in the not too distant future rather than poisoning the food we will inoculate it.

[TSAW]

Interesting article, now I am hoping that my poplar won't be too far gone when I try to use it for projects, anyone with help or advise on this would be glad to listen.  I also have some for a customer who is concerned about his lumber too.

[TSAW]

 

 

 

 

[cutterboy]

TSAW, looks like normal mold to me. The mold should die after the moisture content in the wood drops. When the wood is dry, plane it, that should get rid of the dead mold. Years ago I had  concerns about some maple with mold. A friend of mine planed a board for me and it came out clean and white and beautiful.

[Don P]

From what I'm seeing it could stand to be up higher, out in the open more and have a better lid over it.  That amount doesn't look to be a deal breaker as long as it doesn't get worse. I'm with cutterboy, I don't see more than surface mold, but don't slow down, you're right there if it stays damp for long. Poplar can and will dry fast. Each of those spots is a spore on the wind, landing on moist food and liking what it has landed on. And then, we've had a fair amount of rain and damp weather.

If you were to crosscut some pieces, say a foot or so in from the end so you are looking at the true moisture gradient inside the wood. Pick a piece that is all sapwood. If you see no visible moisture at all in the freshly cut end that means the entire stick is below fiber saturation point. The remaining moisture is bound to the wood cells themselves and is not readily available for the fungi to use. That is the "safe" zone.

The in between moisture is trickier.
Those spores lit on wood that would have been at least surface damp, but fresh sawn it was damp through and through. The fungi gets a foothold, it is on the wind everywhere. The hyphae run in only as far as there is available food(sapwood sugars) and moisture, they can take any path if need be. They will run the rays and then into the deeper wood, their tips can punch right through cells looking for water and sugar. It's a horror movie  ;D. If you dry below fiber saturation before they can run in it shuts it down. If you are drying slower than that you can stop it on the dry surface but it is possible to have it still going inside even though you have stopped it outside with a quick dry or spray.

On the edge grain pic, top board, where the sides of cells are on the surface, not too much got a foothold, where the grain turned and showed more cut off ends of cells you can see blue in the end of every cell, they were all damp and receptive. Bottom pic where the bark was, that is the best food, and the best fungi. Same stick, look at the heartwood, not a speck, no sugar, it needs both. None of that was meant to discourage, more of just random thoughts on the whole subject  :D. You're winning, don't rewet, keep the damp and dew off  .

[Brad_bb]

You just need to dry the external moisture on the surface quickly so prevent this.  That means stacking it where there is sufficient air flow- outside with a breeze, or have a fan blowing on the stack.  That external moisture should dry sufficiently within a couple days? to a week, depending on conditions. Get it up off the ground-I'd prefer 6x6 bunks outside, and make sure it's getting airflow.  I like to keep the stack out of the sun while air drying generally, but one day won't hurt if it's not in the mid 80's and up.

[moodnacreek]

Parking on the grass will rot your truck/car out and stain your fresh cut lumber.

[Don P]

Here's more general info;

Blue Stain - Is it coloring your bottom line red? (widencdn.net)

Blue Stain Fungi - Field Guide to Insects and Diseases of AZ and NM Forests (usda.gov)

This is a Blue stain control product and more good general info.
Sapstain Control - Log Wood Preservative | Schroeder Log Home Supply Inc. (loghelp.com)

[TSAW]

@Don P lots of great info, thanks for your expertise.  This is why I asked the question here because of the depth of knowledge that you all possess.  Thanks everyone for the replies and help.  @cutterboy I had the same thought they should be okay after drying a bit, then plane later.  

Just an FYI these boards are actually ones that I cut for a customer and he stacked, I suggested to get about 6 - 8" off the ground these were stacked right off the mill as soon as they were cut, seems that some got enough of the air flow where others did not.  I will certainly use all the advice here going forward, especially with my own stacks of lumber.  

[Don P]

I grabbed the top booklet here from the USFPL off the shelf on my way to the reading room this morning to see what we forgot... and realized it should be on your bookshelf too;

Air Drying of Lumber

A couple more;

Drying Hardwood Lumber

Drying Eastern Hardwood Lumber

I never got to take classes from Dr Wheeler, but I got to work with some of her students. They gave me those books and several others back before the net. I'm ever in their debt, she realized those boys went to college but more of us went to work, those interns were our access to her depth of knowledge.