Pictures would be helpful...or at the very least a much better description. What do they look like, do they move, can you rub them off, etc.?

Tree branches seldom die only on the underside. This "white stuff" may be lichen spores.

Here is a link that might be useful: Lichens

I read that to mean that the lower branches were all dead...the inside of this weeping tree can be very dense and the older, inside branches can die. In other words, not the 'underside OF the branches', but the underside (inside) branches.

Maybe Joy will get back to us with some pictures or a description.

Must have pictures

How to post them
http://forums.gardenweb.com/forums/load/hosta/msg0513322013993.html?14

Here is a link that might be useful: how to post images

Sorry, here is more. Pictures I do not have as they are so small it only comes out as white paint.

I can scrape them off, yes. They do not move. They don't just wipe off though; it does take some "elbow grease."

Lower branches were never dead before. This tree is like a weed. I trim it back and within a week, a foot of new growth has appeared in many places. It doesn't grow up, it grows across.

Anyway, back to these "things." Like I said, pencil point at best. It's like the bark is painted white. Total coverage, from 2 inch thick branches to little twigs.

I am going to look up lichen spores right now.

definitely not lichen spores. From a distance, like I said,m looks like the branches are painted white. Must get within a few inches to see it covered in immobile white pencil points. I'll try and work some photography magic.

Lacking pictures, you might compare to white peach scale (also attacks cherry).
hortster

I've been thinking peach scale, too, hortster, but without more of a description....

Peach scale doesn't really fit what little bit we know, but at least we know that it can totally cover branches.

definitely not lichen spores. From a distance, like I said,m looks like the branches are painted white. Must get within a few inches to see it covered in immobile white pencil points. I'll try and work some photography magic.

ok, here's the pic. Don't know if it's helpful enough, but it's more helpful than no picture. I scraped of 99% of the 'stuff.'

http://gsa.freeshell.org/IMG_1073.jpg

For some reason, I no longer see a way to attach photos in gardenweb.

Here is a link that might be useful:

You know what, it looks like peach scale as suggested. Thanks! am I right?

ok a forum related question. Why can I not post follow-up's anymore unless I change the subject line. I can't post photos. Why is it so hard to just post to this forum now?

Yes from the pictures it looks like White Prunicola or Peach scale.
Take or send some to your local Extension service for proper ID. In the mean time hit them with horticultural oil. Hit them again with oil in the spring and again when the crawlers hatch, once identified you can find out when this is.
Merit (imidacloprid) as a drench or soil injection will also completely control this scale but that takes time to work so don't skip the first oil application.

From the fuzzy picture, if it is indeed white peach scale I am predominately seeing the males. Females are round, also white with a tan center, under magnification looking kind of like a sunny side up egg. White peach scale is a "hard scale" which means that it is hard to kill it with insecticide unless the application coincides with the emergence of "crawlers" from beneath the females. As to the date of insecticide application, not knowing where you are and your zone, contact your extension service for the likely emergence of crawlers and what to use.
hortster

new york zone 7.

Sheesh, I could have sworn you said they were like small white pencil points! lol. Male peach scales, which are the white ones, are always clearly oblong in shape...quite distinctive. You took a VERY good picture. There's no other scale that looks quite like this.

I'd ask you to ponder most carefully on the recommendation of Imidicloprid drenches. This chemical would need to be applied in the spring when your plant is probably getting ready to flower and it is well known that imidicloprid is translocated to the nectar and pollen of flowering plants, making it a problem for pollinating insects and even hummingbirds.

I think that you will have quite a bit of success with your horticultural oil applications, as long as you attend to your plant three or four times over the fall, winter, and early spring. Be sure to concentrate on getting the product all over the trunk, branches and twigs...nooks and crannies and all. Please use a commercial product specially manufactured to be mixed with water to make an emulsion.

Horticultural oil applications have been the most recommended and successful remedy for a wide variety of scale insects for generations.

Thanks for the feedback Rhizo. You said commercial product. Where do I get a commercial version of horticultural oil?

You can find a wide assortment of horticultural oils at any garden center, nursery, or garden department in a big box store.

I could not resist adding a bit on my Recommendation for Imidacloprid but so as not to hijack this post, started a new one.

Here is a link that might be useful: The use of Imidacloprid