How Things Have Changed

I found an important photograph quite by accident about a week ago. It was on a postcard in The Muses bookstore in Morganton. The photographer is Christopher Smith (www.christophoto.com), who is in Asheville and specializes in weddings and landscapes. I contacted Mr. Smith and he graciously allowed me to use his sopyrighted photo in my blog and my talks on hemlock woolly adelgid.

Why the interest in his photo? It was taken in 2001 at Linville Falls. His photo clearly shows the hemlocks growing in the spring against the dark shadow (note the magnolia blooming). This was before the HWA had made an impact. I didn't have a photo from this time, and even if I didn't, it wouldn't have been that good. You can compare it to my own photograph which I took on Labor Day 2010. The difference? A picture is worth a thousand words, and words can't describe the irreplaceable loss this pest has made in western NC and elsewhere along the east coast.

Chris Smith photo, 2001

My photo, 2010

Needle Drop in Scale Infested Trees

This week I finished taking data on the needle drop in cut branches from scale infested trees. I reported on the experiment on November 10th when I set it up. The experiment worked worked well in that there was needle drop, but since there was too much needle drop, I guess it worked a little too well!

Many of the needles shattered as depicted in the photograph to the left. On some branches, almost all the needles fell off. That is definitely not something we're used to seeing with Fraser fir. If you look closely at this photo, you can see that this was from a scale infested tree, but the uninfested trees were just as likely to shatter -- just not as badly.

The room that the branches were stored in was very hot. It's an unused room at the Mountain Horticultural Crops Research Station office, and both Jeff Owen and I had shoots stored there. They kept the door shut and the room, which faces the sun, would often be too hot to be comfortable in. The shoots in the buckets faired the worse, dropping many needles. The shoots that were were kept dry kept almost all of their needles to the end of the study, but they dried out and became very brittle.

So did scale infested trees drop their needles more than uninfested trees? The quick answer is, "Yes." The results are summarized in the following table which lists the average percentage needle drop for all 15 trees in each group (infested and uninfested) for both the trees stored with water (wet) and without (dry). On average, 43.1% of the needles on scale infested branches had shed their needles while only 27.8% of needles on uninfested branches had shed. Also note in the table that there was more needle drop in the field on scale infested trees (first column labeled "From Field"). I had reported this back in November.

If you look at individual trees, by the end the experiment 47% of the infested branches in water had shattered a third or more of their needles (much like the photo above) while only 27% of the uninfested branches had more than 1/3 needle drop. Of course, that is much more needle drop than would be expected from cut Fraser fir. Remember that these branches spent less than 24 hours without water. Needle shed should have been at a minimum, and was through the first couple of weeks. Only one tree shattered its needles in week 2, and that was a scale infested tree. But by week 4, there were needles everywhere.

If you are a very perceptive observer, you will also note in the table that I only report on 1st and 2nd year needle drop and not 3rd as I said I would do back in November. That is because some of the 3rd year needles were under water in the bucket, and I didn't trust the results from them. In this photo, taken in week 2, the discolored needles had been underwater. These were more likely to fall off.

Generally results were along the lines I anticipated -- more needle shed in scale infested trees -- but the data were far from pretty. After all, there were uninfested branches that totally shattered their needles, and there were scale infested branches with very little needle shed. There were trees where one branch placed in water shed their needles, and the other branch from the same tree also in water hardly did at all. On about half of the scale infested trees, of the two branches taken, the one with more scale had less needle drop. So, I am not real happy with the results. I think I'll repeat this experiment next year either in January or next harvest season to see if I can get some clearer results.

I do think I can safely say the following: there appears to be slightly more needle drop in infested trees. However, needle drop occurs for a variety of reasons, and scale infestation is definitely not the over-riding factor. Still scale infested trees are messy. The scales themselves drop off as the tree dries out. There also appeared to be some fungi growing on older scales as my last picture shows.

This quick little study just confirms what many people had been telling me, that scale infestation doesn't help the quality of cut trees.

Updated Results on Scale Control

I reported in July on some control results of scale treatments I had made on June 20. To recap, I used a backpack mistblower at Dale Cornett's in Watauga County. I used either Asana + Dimethoate, Lorsban, Movento or Safari. In July I went back and the Safari and Asana + Dimethate both gave control, but only about 85% control. This was a bit disappointing. The other two didn't work, but then Movento is a systemic and slow acting, so I vowed to return and see if time would improve the results.

I went back today and now the Dimethoate + Asana and the Safari both had 100% control. I did not see any live scales at all. It was hard to find shoots that had scales on them, and they all looked dried up just by looking at the shoots. There was no white cotton at all.

The Lorsban and Movento treatments were still similar to the untreated check trees. They still hadn't worked.

So not only did control improve with the Safari, it did with the Dimethoate + Asana as well. Maybe we go back too quickly to evaluate control. These materials apparently keep on working.

Remember that currently Safari does not have a Christmas tree label -- only a nursery label. So if you aren't digging your Fraser fir, you're not supposed to use it. Hopefully that will change next year. These results are certainly encouraging.

Research out of Connecticut has indicated that Safari will controls scales with a trunk application, at a reduced rate per acre. These treatments can be made in April through June. I plan on trying this next year.

Scales & Needle Drop

Why does Meghan Baker, Watauga County Extension Agent look so happy? We were done collecting shoots! Meghan helped me on Monday collect shoots from a grower's field to help determine if elongate hemlock scale infested trees are more likely to drop their needles after the tree is cut. Several growers and Christmas tree retailers have told me they think scale infested trees are more likely to drop their needles. Other pests such as spider mites and balsam woolly adelgid cause similar problems. Hopefully we'll soon know if it's true of elongate hemlock scale as well.

Meghan and I collected shoots off of 15 infested and 15 uninfested trees. We took three years worth of growth plus a little bit of the fourth year branch in order to stick the shoot in our trays. Since scale goes back multiple years, we wanted to see how it was affected older needles.

Our samples were paired. We took two branches from one area on the tree and another set of two branches from another area, usually on the opposite side of the tree. One of the paired branches will stay in the bucket with water. The other one goes in a tray without water. Having two sets of these pairs will allow us to compare results within a given tree. Needle retention varies greatly between trees even without pest infestation. It can also vary with different positions on a tree. Most of our samples came about 1/2 way up the tree and some branches I cut were practically against the trunk.

This is what all 120 shoots look like today. Each branch is labelled so I can keep track of what tree they came from. Half of the branches are in buckets of water and half in styrofoam trays without water. Yesterday I took data on the scale infested branches, estimating the percentage of needles with scale on the 1st, 2nd, and 3rd year growth. Infestation varied widely. I have some branches with 2nd and 3rd year needles having 100% infestation, and others with less than 25%. I also marked if there were other problems with the foliage such as twig aphid damage or small, yellowed needles that are also more likely to shed. If there was any needle drop already, I also made note of that.

In a week I will take each branch and lightly rub my hand over the foliage and estimate the percentage of needles that fall off, again keeping track if they are from the 1st, 2nd, or 3rd year shoots. I'll take ratings again after 2 weeks, and final data after 4 weeks. Already I'm finding that the 3rd year needles of heavily infested trees were falling off the trees in the field. These trees are such heavy density so it probably wouldn't have mattered, but if they keep coming off in the home, it will cause a mess.

I want to give special thanks to Jeff Owen who has conducted several experiments like this looking at other factors affecting needle drop. He was able to help me with the experimental design. Much of this type of research was originally conducted by Drs. Eric Hinesley and Gary Chastagner. And of course thanks to Meghan for her help, and for the grower, Johnny Greer, who donated his trees. Also a big thanks to the Mountain Horticultural Crops Research Station at Mills River who are donating some space in a spare room to mimic someone's home. (I promise to sweep up all the needles!)

I'll let you know how it all turns out.

More Algae Control Results

Jerry Moody, Doug Hundley, and I rated the trees treated in Avery County for algae control today.

Treatments. The treatments are all listed on blog posting from August 27. But I'll list them again here.

1. Untreated check
2. SA-20 disinfectant @ 1 teaspoon per gallon on May 5
3. Daconil @ 3 pints per acre on May 5
4. Dithane @ 1.5 pounds per acre on May 5
5. Kocide @ 3.5 pints per acre on May 5
6. Kocide applied twice on May 5 and May 19
7. Kocide on May 19
8. 3% bleach solution on September 25
9. Kocide on September 25

All treatments were made with a backpack mistblower except for the 3% bleach solution which was applied with a high pressure sprayer.

How we did it. Taking ratings was  hard. After all, some trees don't appear to get algae at all -- whether because of their position in the landscape, their proximity to other trees, or resistance is anyone's guess. So we first looked to see if the trees had algae on older needles. The trees with algae on older needles are the only trees we counted in the data. Then we looked specifically at 2009 growth and gave it a rating of 0 to 4 where 0 = none, 1 = very light, 2 = light, 3 = moderate, and 4 = heavy. We examined 15 trees in each treatment.

Results. The results are to the right. Remember that we only counted trees that had past algae. So, the higher the pecentage of trees with no algae in 2009, the better the product was working. And obviously the lower the algae rating, the better the product worked.

The best controls were with SA-20 disinfectant and Kocide applied May 5. The Kocide applied later in May didn't work as well. Nothing worked in the fall. Again, these materials will prevent algae from developing, not cure it.

These treatments were applied to a single row and the treatments are in order going up the hill (all except for the check row which was between the Daconil and the Dithane). There was definitely more algae the farther up the hill you went, and so that may be why SA-20 disinfectant worked well. That's also why the fall applied treatments had more algae than the check.

What next? I'd like to look further at Kocide and perhaps some disinfectants next spring. I'll also be looking for some growers who will be interested in trying the Kocide. Unfortunately it looks like if you want to control algae, you need to treat for it the last 2-3 years before harvest every spring. Once it occurs, there is nothing you can do about it. Treatments will be harder to make on large trees growing together, and in fact this is where we find the most algae. So keeping a good spacing between trees is important.

More Info on Fall Needle Shed

Jeff Owen sent me the following information to further discuss what's happening with fall needle shed:


Stressed Fraser firs will shed interior needles in late September or October. It usually occurs right in line with fall color on hardwood trees. Usually it is a sign of drought stress, but there may also be a fertilizer deficiency or toxicity contributing to the problem. We have not been able to point to a single nutritional problem contributing to interior needleshed. But I have seen internal needle shed in fields that have low phosphorus, or calcium, and/or very high manganeses or sulfur. 

I have observed several fields where the needle shed is widespread on the southwestern aspect and very light as the field shifted to more of a northern aspect. Even a subtle difference in aspect made a big difference in this problem. In a drought stress year, most growers will have 1 to 5% of this problem in their older trees, but I have seen one or two fields with as much as 30% of the trees affected.

Needle loss problems seldom show up before trees are of a marketable age and size.  Trees greatly increase the amount of foliage with each progressive year.  This creates an increasing demand for water and nutrients.  Factors which may have been adequate or marginal for a smaller tree become limiting as the tree grows.  The failure of symptoms to be expressed in younger trees has often lulled growers into complacency only to be surprised by needle loss in trees already tagged for market.

When needles shed out to the new buds in the fall, I think it is a different scenario. In that case I have observed 3 different factors in play: salt, calcium deficiency, and Phytophthora root rot.

Salt injury at some time in the current year can cause needle loss all the way out to the bud typically without killing the branch or bud (although sometimes they die too). I have seen late fall needle loss and grey-black necrosis in the bark and wood of branches that were spring fertilized with "plops" of 10-10-10. Sometimes the whole tree sheds, but sometimes only one side or a coil of branches climbing up the stem from damaged roots will lose needles.

Calcium deficiency will induce fall needle loss in the top or middle of a mature Christmas tree. I have seen white pine and Frasers with similar symptoms in the same field. All the needles on a branch can turn bright yellow, then brown, then drop off. The branch and buds live although growth can be stunted in the following year. I have seldom seen more than 1% or 2% of trees with symptoms of calcium deficiency. Yet these trees may reflect a field-wide deficiency. The concern has been that other trees in the field that showed no symptoms prior to harvest could shed needles after harvest either on the retail lot or in the  home. Dr Hinesley and Dr. Shelton conducted unpublished research that suggested this was the case.

The third root cause of total needle loss that I have seen was Phytophthora root rot (PRR). Usually, Fraser firs that die of PRR hold on to their needles a long time, but sometimes in the fall when the diseased trees have been stressed, green trees will shed out just like they do with a calcium deficiency. Only healthy roots can actively take in calcium, so it makes sense that PRR can contribute to the expression of calcium deficiency.

In all of this there are few proactive steps to take. In terms of the imediate harvest, buy a shaker machine to remove interior needles on trees that are still salable. For the future, take a soil sample and fertilize your farm according to the reports. Don't let market trees go to harvest short on calcium.

Fall Needle Shed

I'm getting out of my comfort zone talking about fall needle shed. I don't think we have a good explanation as to why it is happening. It is certainly associated with stress and is worse in some years (like this one) and in some fields than others.

Of course some needle shed occurs every fall. Usually it's the 4th or 5th year needles. The problem occurs when it's the 3rd, 2nd or even the current year's needles. That's when tags start coming out of trees!

These photos are ones I took with Jerry Moody on Friday at a high elevation farm in Avery County. The site was above 4,000 feet, and it was very windy -- that means a stressful site. Though these pictures were taken in Avery, I've heard of a lot more problems in Ashe County where it has been drier this summer and fall.

This tree had only a few areas that had discolored needles.

This tree had excessive shed throughout the whole canopy. It was a very heavy density tree, so it was hard to see from the outside, but it will still impact if this tree can be sold this year.

In some instances we've seen trees like this with current year needle drop that were due to root injury. Fertilizer burn can be one cause of root injury, but this particular field had not had any fertilizer applied since the spring. The shoots of this tree appeared to be healthy, as did the buds for next year. Root loss can also be caused by drought. Fraser fir, being a seed-run crop, will have individual trees that are more susceptible to drought than others.

I've had some calls from growers that are concerned that scales are causing this discoloration. At this site, there were no scales. If in doubt, look at the shoots of several trees. Turn the foliage over to look for the presence of scales. Most of the fall needle problems have not been associated with scales.

Advice for the grower? Keep on top of your fertility. By fertilizing according to soil sample results, hopefully you can avoid many of these problems. If the problem develops, take soil samples and plant tissue samples of healthy verses trees with shedding needles. And get your County Extension Agent involved.