The Value of Christmas Trees

"...there is no reason why the joy associated with the Christmas evergreen may not be a means of arousing in the minds of children an appreciation of the beauty and usefulness of trees; and keen appreciation of the beauty and usefulness of trees is a long stop toward the will to plant and care for them (Arthur Sowder, US Forest Service, 1949)."

Wednesday, January 27, 2010

Elongate Hemlock Scale Trials 2009

Photo captions from left to right: Female scale flipped over to show small area, outlined in yellow, through which the scale feeds. Male elonagate hemlock scales produce a white, fluffy covering which can bee seen on the needles and may affect sales. Field shot where scale spread has been monitored over a 12-month period

SUMMARY: In 2009, a series of pesticide trials were conducted to determine timing and materials for scale control. Results indicate that the best scale control is achieved in the summer. Scales can be controlled in the spring, but there will be 5-15% less kill. Treatments made after mid-September also do not result in good control. The best materials for control continue to be Dimethoate plus either Asana or Prev-Am. However, in a fall applied trial, Lorsban gave excellent results. Safari has given variable results, as has the new insecticide, Movento. Horticultural oil continues to give control at about 65-75% kill. At one field site, scale spread to as many as 1/3 more trees from the summer of 2008 to 2009. However, tree growth appeared to be hardly affected. Current control recommendations are found at:

Elongate hemlock scale (EHS) has continued to spread in Christmas tree farms in western North Carolina. I had hoped that a cold winter last year would reduce scale numbers, but that was not the case. I have been conducting EHS control trials since 2003. This past year, I had 4 field trials looking at different materials for scale control as well as assessing scale spread in a 5th field.

Past work has indicated that a mixture of Dimethoate (@ 16 ounces per 100 gallons -- a pretty hot mix) + Asana (@ 10 oz/100 gallons) or the Dimethoate + Prev-Am (@0.4% solution) gives good control in the summer. Last years trials really confirmed that the Dimethoate by itself does not work as well, nor gives as long lasting controls. Past work also indicated that the best control would be achieved in the summer (July through early September). Treatments made in 2008 in the spring did result in good control (92% of scales killed in one test), but slightly better results were achieved in the summer.

Most Christmas tree growers are well acquainted with Dimethoate and Asana. Some may not know as much about Prev-Am.

Prev-Am is an insecticide, miticide and fungicide. It is produced by Oro Agri and is made by a mixture of "Borax, cold-pressed orange oil, and various biodegradable surfactants." According to company reps, Prev-Am will disrupt the exoskelton of the insect. It also will increase translaminar movement of products across the surface of the needles, and reduce surface tension, thereby improving penetration. More information about this product is available at the Oro Agri site at: The Prev-Am is not considered an organic product because of the amount of borax. However, it certainly smells good. It can help mask the smell of Dimethoate. It probably aids Dimethoate by increasing the penetration of chemical into the scale. However, we have seen needle burn a few times when it is used at the full labeled rate of 0.8%. I have not seen burn at lower rates, and so have recommended the 0.4% solution to mix with Dimethoate.

The first picture aboves shows why it is so hard to kill these scales. They are armored scales, but they are covered both on top and underneath. There is only a small area (outlined in yellow) through which the feeding tube fits, and the scale is not protected. The Prev-Am may help in getting materials through to the scale to kill it.

Anyway, that's where things stood at the start of 2009. There were still a lot of questions about scale control. When does the treatment window "close" in the fall? How much will EHS spread in a year? Can the rate of Dimethoate be reduced when using Prev-Am? What other materials can be used for control? And could a grower get as good control with a back pack sprayer as a high pressure sprayer? Jerry Moody wanted this question answered especially as he had several folks with localized scale, and they just wanted spot control.

What were some of these other materials? In 2009 we looked at Movento, Safari, Mavrik, Talstar, Lorsban, and Vintre as an adjuvant to Dimethoate.

Movento (spirotetramat) is an insecticide labeled last year by Bayer. This product is supposed to be an excellent systemic, but it requires the use of a surfactant. Also, they were recommending it be applied twice, with applications made 2 weeks apart. (Some of you may know that Movento labeling issues have arisen. A judge stopped the sale of Movento, because there was not proper public comment posting by EPA. This has been stayed until mid-February, and the company hopes that all labeling issues will be resolved. In the media, there were reports the stop-sale occurred because Movento kills bees. Well, practically everything kills bees. Even spinosad, an organic product, is highly toxic to bees. However, most materials applied in the evening after bees have stopped their activity do not end up harming them).

Safari (dinotefuran) is a neonicotinoid similar to Merit (imidacloprid), the product most often used for hemlock woolly adelgid control. Jerry Moody and I tried it against balsam woolly adelgid, and it worked very well. Research from other states indicated that it was controlling EHS in hemlocks.

Mavrik is another synthetic pyrethroid that Jerry Moody was interested in. Talstar is also a synthetic pyrethroid similar to Asana. I didn't think it would work as well as Asana, but I didn't know for sure.

Lorsban is an organophosphate which I didn't think had that much activity against scales, but which Bryan Davis said folks in Michigan were recommending for scale control. Also, the folks at Oro Agri wanted us to look at another product of theirs called Vintre which doesn't contain Borax and is labeled for organic production instead of the Prev-Am.

I ended up with 4 pesticide trials for EHS control. One was applied in the spring, one in the summer, and 2 in the fall. The spring applied trial (April 28) was mostly to look at Movento. In the summer (July 7 and boy howdy was it hot!), Bryan Davis and I put out 7 different products. At the end of August (the 26th), Jerry Moody and I put out different products with either the back pack sprayer or a high pressure sprayer. Then in early October (the 8th), Bryan Davis and I tried a few products to determine if the treatment window really was closed.

I'm not going to list all the treatments, rates, treatment dates and results as it gets confusing. But I will summarize the results. The best controls (96%+ kill) were with Dimethoate plus either Asana or Vintre in the summer. Dimethoate worked well at both rates -- either 8 or 16 oz/100 gallons when mixed with the Vintre. In the past, lower rates of Dimethoate haven't worked so well with Asana. The Vintre, used at 0.5% solution did cause burn, so I'm going back to the Prev-Am.

Safari and Movento gave variable results. Movento applied in the spring with 2 appliecations made about 14 days apart, gave good control. But when applied just one time in the summer, it didn't. I think we still need to play around with the adjuvants used with Movento until we find the right one. Maybe Prev-Am would work.

Safari when applied in the summer with the Vintre gave good control, but when applied in either August or October -- and without the surfactant -- didn't. Safari's control may take longer than I give it, however. Last year, Jerry Moody had a grower that treated his farm with Safari, and when I went out about 6 weeks later, his EHS control was poor. However, when we went the following spring to pick out a site to spray in, the scales were all gone. So I plan on rechecking these results this coming spring. Also I plan on looking more at both of these materials in 2010.

What didn't work at all? Mavrik didn't, and Talstar + Dimethoate wasn't as good as Asana + Dimethoate. A new encapsulated oil called Saf-T-Side didn't control the scale any better than oil normally does, but it also didn't cause needle burn when applied on a very hot day. Because of these results, I plan on looking closely at Saf-T-Side for twig aphid control ithis spring.

There were a couple of surprises. The real surprise for me was the Lorsban. When applied in early October, it cooked them. I definitely want to work some more with this product in 2010. Another surprise was at the field trial applied in August, control was actually better using the back sprayer than the high pressure sprayer. But then, I was really soaking those handful of trees down. That just proves again the coverage is everything.

The real questions remains, how big of a problem is EHS really? It is definitely spreading, both in Fraser fir and in hemlocks throughout the mountains of North Carolina, and I think in Tennessee and Pennsylvania as well. At one farm (pictured above), Bryan Davis and I flagged trees the summer of 2008 that had scale on them. Then I went back this summer with Meghan Baker, the County Extension Agent in Watauga, and looked at which new trees had scale. In 2008, 26% of the trees had scale and in 2009, 54% did. But several of the trees flagged in 2008 didn't appear to have scale in 2009, and so the real increase was 33%! But even though scale was spreading, the trees actually looked better the summer of 2009 than they did the summer of 2008 -- just because they finally had some rain on them. The trees hadn't been sheared yet, and so I measured the terminals of all the trees. The average terminal growth for trees with scale in 2008 and 2009 was 16.9 inches. For trees with scale only in 2009, terminal length average more -- 19.1 inches. Trees with no scale at all (maybe they are growing so poorly they make bad hosts) had an average length of 15.6 inches. So perhaps scales are reducing growth somewhat, but not that much.

That begs the question -- why control scale then? I think the biggest reason is the unsightly white fuzz that gets on trees in the summer (pictured above) when the males are mostly produced. Christmas trees have to be pretty, and this fuzz is not. Also, trees with scales can't be shipped out of the country.

So what are my current control recommendations? I have them all written out in a new Christmas tree note on the Elongate Hemlock Scale found at:

Of course there are still unanswered question. I guess I be looking at a lot more scales in 2010!

Monday, January 25, 2010

Interesting Results with Safari for Woolly Adelgid

Picture caption: Field site where Safari was applied in July, 2009 was heavily infested.

SUMMARY: Safari controls balsam woolly adelgid well, and may work well even with incomplete coverage. However, more research is needed.

Safari (dinotefuran) is one of the neonicotinoid insecticides. Their mode of action is similar to the natural insecticide, nicotine. The most commonly used neonicotinoid is Merit (imidacloprid) which many people have used for hemlock woolly adelgid (HWA). Safari, however, is far more water insoluble than Merit, and control of HWA has proven to take weeks instead of months as it does with Merit.

In fact, researchers are now applying Safari in a spray form just to the trunk of the hemlock and getting good control. Now that's quite a systemic if the chemical is moving through the bark and up to the needles.

Jerry Moody, the CEA in Avery County and I tried Safari against balsam woolly adelgid (BWA) 2 years ago, with very good results. Oddly, this material will not control twig aphids. How something is so good against adelgids and won't control aphids, I don't understand. It is also labeled for scale control, though control of elongate hemlock scale has been variable. (I will talk about that more in a future post).

In any case, Jeff VAnce, the CEA in Mitchell County and I decided to try Safari against BWA in a field trial this summer. We mixed Safari at 8 oz/100 gallons and then applied it one of three ways -- with a thorough spray, only hitting the trunks (and using about 1/2 the water and moving twice as fast), or not spraying the tree at all but just hitting the ground. The treatments were made July 1 with a high pressure sprayer.

I never thought it would work. After all, systemics don't work as well against BWA as they do against HWA because BWA is feeding in the bark and not the needles. However, it did work well.

Before anyone gets too excited, remember that we had an awful lot of rain last summer. This may have allowed the chemical to get into the tree better than it would in a normal year. The results are exciting, and we will try it again this year.

Friday, January 22, 2010

Fall Treatment for Twig Aphids

Captions of photos from left to right: Hatched twig aphid egg. Dead twig aphid next to hatched egg. Normal twig aphid egg.

SUMMARY: Research I've conducted the past 4 years has helped determine that twig aphids are controlled when pesticides such as the synthetic pyrethroids are applied the fall before. Changes in recommendations for twig aphid control are found at
Research conducted in 2008-2009 involved careful twig aphid egg observations to determine why this works. Observations determine that Talstar-treated eggs were developing into aphids, but these aphids were dieing upon hatching. It is still not known why this is happening.

Another project that's been going on for several years now is the fall treatment of twig aphids.

This really started because of rust mites. Several of the materials that people were using for balsam woolly adelgid (BWA) control including Asana and Talstar were creating problems with rust mites when applied in the spring. But Doug Hundley, the IPM extension technician in Avery County, observed that when these materials were applied in the fall, there were far fewer problems with rust mites.

Why are rust mites affected by these materials? We really don't know. One would assume it has to do with these broad spectrum synthetic pyrethroids killing off natural predators. However, we really don't see a lot of predators feeding on rust mites. So though I don't really know the why, I do know that this observation has been made again and again and does appear to be real. Rust mites are of course a spring time pest, active primarily in March and April, and would be affected when BWA/twig aphid sprays are applied during this time frame.

In any case, this observation of Doug's caused many growers to start applying BWA controls in the fall. The result? A lot of folks began suspecting that they were having fewer problems with twig aphids the following year. So I decided in 2006 to determine if this was something that was really happening or not.

Honestly, I didn't think it would work. After all, in the fall twig aphids are in an egg stage that is not anywhere near hatching. These eggs won't start hatching until mid-March. Therefore they aren't respiring much. A pesticide shouldn't affect them. Also, the materials that were being used shouldn't last until spring to finally kill the aphid that hatches out. Research has determined these materials will last 4-6 weeks depending on the weather. Therefore, based on what I knew about twig aphids, pesticides and how they work, treating trees in the fall shouldn't work.

By the spring of 2007 when observing the trees Bryan Davis and I treated the fall before, it was quite obvious that it was working. The synthetic pyrethroids and especially Talstar, resulted in virtually no live twig aphids and no twig aphid curl.

Numerous studies and farmer's observations since then have confirmed this. Like one farmer told me last spring, he had the best twig aphid control he'd ever had by treating the fall before.

So how does it work? Frankly, I still don't know. That's one thing I tried to figure out in 2009. Doug Hundley, Jerry Moody and I set up a field study in fall of 2008 where we sprayed a block of trees every month for several months. Treatments included the following:
  • August 18, 2008 (applied Talstar @ 40 oz/A)
  • September 19, 2008 (applied either Talstar or Mavrik @ 5 oz/100 gallons)
  • October 31, 2008 (applied either Talstar, Talstar + Envidor for rust mites control @ 24 oz/A, Mavrik, or Thionex @ 24 oz/100 gallons)
  • March 20, 2008 ( applied either Talstar, Talstar + Envidor, Mavrik, Thionex)
There were untreated blocks for each of the treatment dates. That resulted in 16 different blocks of about 80-100 trees each and lots of pretty flagging everywhere. I don't think anyone but myself could figure out what was going on, and sometimes I wasn't too sure myself!!!
The spring of 2009 starting in February, I started evaluating twig aphid eggs from each of these plots. I collected 30 shoots from each of the 16 blocks and looked at each for the presence of twig aphid eggs. And beleive me, it was sooooo scientific. I took a pin and poked each one to determine if it looked normal or not. :-)
Data I took included if the egg was full, flat (and presumably non-viable), hatched, blackened inside (definitely not normal), or if I was pushing out of the egg an aphid that was almost ready to hatch. I did this on February 1, March 9, March 24, and April 4. I looked at the eggs the same day I collected them. And of course, I also made note of any rust mites that were present.
Of course when I was doing this, I still didn't know if any of these treatments actually controlled twig aphids. It ended up that all the treatments controlled twig aphids as compared to the untreated checks. Date of treatment with Talstar and Mavrik (another synthetic pyrethroid) didn't matter. The Envidor didn't help as rust mites didn't develop in any plot except when Talstar was applied in August when we didn't also include a plot with the Envidor.
So what did I learn from observing the twig aphid eggs? In all, I looked at 1,368 eggs. But with all this work, I didn't answer my questions.
On the earliest observation date (February 1), there were essentially no differences between any of the plots -- treated or untreated. There were a lot of eggs both treated and untreated that looked flat, in other words like they were no longer viable. But healthy looking eggs were all full of clear liquid. They looked like little balloons that were popping.
By March 24, there were live aphids in the untreated plots and there were some differences between Talstar treated plots and untreated plots. There were 14% of the eggs that looked black inside instead of clear with Talstar treated trees as opposed to just 2% of untreated trees. But there were still 22% of the eggs that when poked, a tiny aphid was apparent inside the eggs ready to hatch (11% of eggs in untreated plots).
Apparently, these fall Tastar treated eggs are in many cases starting to develop into an aphid just as if they weren't treated. But these aphids don't survive. They die after hatching. Why I don't know. Are these chemicals lasting until spring to kill the aphid? Are they associated somehow with the egg? I just don't know.
There were some dead aphids right next to Talstar treated eggs. But there were a few dead aphids found in untreated plots too. Perhaps they die from cold or other causes.
I have another site set up the fall of 2009 where I plan this spring to follow the condition of the twig aphid eggs to see if I will make similar observations.

Tuesday, January 19, 2010

Horticultural Oil for Spring Pest Control

SUMMARY: Horticultural oil sprayed in mid March gives good control of twig aphids and rust mites, and will reduce problems with spider mites and balsam woolly adelgid.

For the past couple of years, Bryan Davis, IPM technician in Ashe, Alleghany and Watauga Counties, and I have been playing around with using horticultural oil for twig aphid control. Bryan first heard of this technique when he gave a talk in Maine. Tree growers up there regularly use this method for twig aphid control. But their weather, pests and trees are different than ours. Would this same technique work here?

The answer has been an overwhelming -- YES. Spraying trees in mid-March with a 2% oil solution has resulted in excellent twig aphid control without causing burn. That is, if the agitation is sufficient. And what do I mean by excellent control? In one test plot conducted in Avery County last year with the help of Jerry Moody, there were no curled needles at all. In Bryan Davis' own trees where he was getting good enough aggitation, there was again, virtually no twig aphid curl.

So how is oil controlling twig aphids? This is a twig aphid egg that has been sprayed with oil. It is the black thing in the middle that kind of looks like a raisin. It looks a lot different from a healthy egg which is plump and has white, waxy rods scattered across it. This egg will not hatch in the spring.
A 2% oil solution is also quite effective at controlling hemlock rust mites. In fact, oil is every bit as good as some of our other miticides such as Sanmite and Envidor. Oil will also reduce problems with spider mites, and control balsam woolly adelgid.
The trick is to apply the oil before the twig aphids have started to hatch, as it is not as effective against the aphids as their eggs. Early to mid March is a safe time to apply. By the end of March, some aphids will be present. I haven't gone as early as February with a treatment, but may if the weather cooperates.
There are 2 down sides to using oil. One is that you have to use a high pressure sprayer. Though I haven't tried it personally, I don't think that there will be good enough coverage to get control of pests with oil applied with a mistblower.
The other down side is potential for burn. Frasers are very sensitive to burn by oils and pesticides. If there isn't good enough agitation, even dormant trees will be burned. After all, oil and water don't mix. However, there may now be a solution.
Even if you don't get burn, there is a distinct change in the color of the trees. It's not that the trees look bad, but on a sunny day you can definitely tell that the trees have been sprayed with oil.
Saf-T-Side oil is an encapsulated oil that mixes readily with water. It is more expensive than regular oil, but it appears to be much safer. I tried it last summer on a hot day in July for elongate hemlock scale control, and though several other products burned the trees, this oil did not. I haven't tried it for twig aphid control in the spring yet, but I plan to this spring. I don't see why it wouldn't work. After all the July spray with oil gave the same results you would expect with a regular oil -- about 65% control. I'll let you know how it works.
This method of pest control will work well with organic Christmas trees. If you try it, be sure and scout from mid to late April to make sure twig aphids aren't showing up.

Monday, January 11, 2010

This Winter's Weather

SUMMARY: The harsh winter weather this year will help decrease problems with Phytophthora root rot and Cinara aphids, but probably not other pests. And even these pests aren't eliminated by the cold.

Doug Hundley sent me this picture of his trees during the Christmas Day ice storm.

I'm sure a lot of folks are wondering what the weather this winter will mean to pests of Fraser fir Christmas trees.

Of course last winter we had even colder temperatures, though they didn't last as long. I have pictures of the creek near my house taken January 2009 with ice over about half of it, but so farthis year, little ice has shown up on the creek .

I was hoping last year that the cold temperatures would reduce elongate hemlock scale, but they didn't seem too. Of course, when you examine the scales under the microscope, there are always a lot of dead indivduals present. Last spring after a cold winter, I think the percentage of dead scales was higher than I usually observe -- sometimes as high as 45%. But the scale still spread successfully. At one farm, there were scales on 32% more trees the summer of 2009 than there had been in 2008. So cold weather may slow scales down some, but not enough to get excited about.

Cinara aphids are one pest that do appear to be less common after a harsh winter. There weren't many fields that had Cinaras in 2009. Those I did see didn't have aphids until fall. Even so, I still had close to 10 calls about Cinaras before Christmas 2009. So though they aren't prevalent, they can still be a problem.

One pest that cold winter weather does help with is root rot. Research has clearly demonstrated that Phytophthora cinnamomi resting spores will slowly die as soil temperatures remain below freezing. The longer soils are frozen, the more spores will die. This can be a big benefit to Christmas tree growers this year. But again, there will always be a few spores that survive, and given the right conditions of warm weather and flooding, those few spores can still cause quite a problem.

Other pests are well adapted to cold mountain temperatures. That includes about everything else -- woollies, twig aphids, spider mites and rust mites. The only time these pests seem to be affected by cold temperatures is if they start to become active in the spring, and then they are caught by a winter storm. For instance, during the blizzard of 1993 which occurred in March, rust mites on hemlocks were killed out and ended up not being much of a problem that year. However on the white pines that caught and held the snow, the mites were insulated and ended up surviving.

The same can happen in the fall -- if it's warm and pests remain active late in the season and then freezing temperatures suddenly occur, they can be killed out. That didn't happen this fall. We'll have to wait and see what the spring brings!

I plan on going out this week to see how elongate hemlock scales are fairing if I can make it to the field I'm monitoring. I'll report on what I find later this week. I'm especially interested to see what stages are surviving this weather, and if any crawlers or many eggs are found.

Friday, January 8, 2010

Updates on Web Site

In November I updated a lot of Christmas tree notes on the Christmas tree web site ( based on new approaches to pest control in Fraser fir. I'll go into some of the on-going research in later posts, but I wanted to make sure that everyone knew what was new so they could take a look at them. They are:

CTN #8: Control of Root Feeding Insects in Fraser Fir Christmas Trees

CTN #19: Balsam Twig Aphid on Fraser Fir

CTN #20: Balsam Woolly Adelgid

CTN #29: Spruce Spider Mite on Fraser Fir

CTN #34: Rust Mites on Christmas Trees

Cinara aphids on Christmas Trees in North Carolina

What are the main changes?
  1. Updates on which pesticides are available -- we've lost some and added some.
  2. Recommendations for controlling twig aphids in the fall.
  3. Using horticultural oil in mid March to control twig aphids, mites and woollies.
  4. Root dips for white grub control.
There are more updates that will hopefully be ready this spring. If you ever find any broken links on this web site, please let me know!

Thursday, January 7, 2010

Getting Started

I've been working with Christmas tree IPM in western North Carolina for more than 20 years. As Extension Specialist with North Carolina State University, I've given a lot of talks, taught a lot of folks to scout, written articles and fact sheets, conducted demonstrations, surveyed growers, done field surveys of pests, predators, stream insects below tree farms and even rodents in tree fields -- all the things you're supposed to do to learn better ways of controlling pests and helping growers do a better job.

These twenty years have seen a lot of changes in the Christmas tree industry. I'm probably prejudiced, but I think our North Carolina growers do better than anyone other growers in the country with IPM in Christmas trees. They are leaving more ground covers around their trees, have reduced pesticide use tremendously through the years, and really try to grow a good tree in a manner that's safe for the environment and safe for their workers.

What's exciting is that there's more to learn all the time. Every year I and the County Extension Agents and Technicians I work with make new discoverys that can help growers do an even better job.

But increasingly, I'm finding it hard to get the word out. There is so much information and it changes from year to year. Growers can't make every meeting. Everyone has too little time and too much to keep up with.

That's why I'm starting this blog. I want to get the word out in a timely manner to my audiences -- which include County Agents, growers and even the public -- and I thought a blog would be a more informal way to do that. I plan on making posts that starts out with a summary for a quick overview for those that don't have a lot of time, and then a longer version that includes all the details. I hope by the end of 2010 to have a record of what's been happening in Fraser fir IPM that will help everyone keep up-to-date.