Beating Trees to Beat Bugs

SUMMARY: To decide what insecticides to apply in the spring, it is important to scout in April to determine if twig aphids and mites are present in a field. Use foliage beats for twig aphids and examine shoots for rust mites and spider mites. Always use a hand lens. Though scouting takes time, it will end up saving both time and money by helping to determine exactly what pesticides, if any, are required.


I finally made it to Ashe County yesterday. It was good to at least make it into Christmas tree country again. I saw several blue birds which is always fun.

Bryan Davis and I chatted with some growers who had treated different blocks of trees with Dimethoate + Asana at different times -- anywhere from the end of June through mid September. They wanted to know if they had controlled the elongate hemlock scale and if they could skip twig aphid treatments in the spring. It will provide us a great opportunity to evaluate different timing of these materials for both scale and twig aphid control. After all, most of the fall treatments that have been followed over the last several years have been with Talstar, not Asana. It will be interesting to see under different conditions how well the Asana performed. But our conversation also made me realize what all growers will be facing this spring.

Of course it's so snowy, you can't even get out in the field now, even if you could tell anything about pest control. If you can make it to the field, there is a layer of ice on the snow that makes walking difficult. People are sitting around knowing they are already getting behind this growing season before it even gets started. In the spring, growers need to plant, fertilize, get herbicides out and insecticides. Some even have a bit of shearing that needs finishing. I'm afraid, scouting may be one of those things that doesn't end up getting done.

How do you get it all done when you don't have the time? Fortunately, scouting doesn't have to take a lot of time. The two most important pests a grower needs to evaluate in the spring are twig aphids and rust mites. Neither should take a lot of time to assess. As pictured with this post, taking beats of foliage on just a few random trees in each block will let you know if fall treatments with insecticides have controlled twig aphids. Start this in mid-April.

This photo shows a beat with a lady beetle larvae (the big bug) and four twig aphids (one fairly big and three small). Always use a hand lens when you look at what fell out. If you find more than a couple of trees with twig aphids, you will need to treat again in the spring. At the same time when you look for twig aphids, pull a few shoots and look with a handlens for rust mites. If there are only a few, make a mental note to check again in a few weeks to see if the numbers are increasing. Remember that rust mites are very small. If you are just looking at foliage beats, you'll miss finding all but the heaviest populations of rust mites. By taking both foliage beats and pulling shoots, you will also learn if spider mites are a problem.

The fields I mentioned earlier that had had Asana in the summer or fall are much more likely to have rust mites this spring -- but there's no reason to assume mites will cause enough damage to worry about. The earlier the Asana was applied, the more of a problem rust mites are likely to be, so we advised the growers to scout those fields first. But if this spring stays fairly cold and wet, rust mites might never become a problem. As I start getting out in the field in March, I'll let everyone know in this blog what this spring looks like as far as rust mite pressure in general.

Unfortunately, some growers seem to be skipping scouting, and just treating everything in the spring with Dimethoate + Thionex, thinking that these two materials will control everything. After all, Dimethoate will control spider mites, rust mites, twig aphids and some scale, and Thionex will control twig aphids and woollies, and neither is that expensive. But remember, Dimethoate's control of mites can be short lived, and Thionex gives no added help with scale control. Twig aphid control with Thionex has been variable, and we're not sure why. These are also the two most toxic insecticides that growers use, and they also smell really foul, making them an issue with neighbors. And why spray anything at all if you don't need to? If you treated last summer and fall, you might not need to treat again this spring. And even if you didn't, twig aphids and mites aren't always a problem every spring.

Scouting takes time, but it also saves time, money and pesticides. If you aren't confident about scouting, call Extension for help. There are also scouts working in the counties that can be hired to do your scouting for you. For their names, call the County Extension Agents in some of the bigger tree counties.

I hope to get out to the fields we talked about yesterday and some I treated last fall starting the second week in March. I'll let you know what I find. In my next post, I'll go over some of the pesticides and timing that can be used for pest control this spring. But remember in April, to take your beat sheets (white plastic plates work great --thanks for that tip Doug Hundley!) and hand lens with you.

If You're Missing Di-Syston...

SUMMARY: If you are treating for twig aphids this spring, there are many choices available both in pesticides and spray equipment. It is not necessary to treat trees for twig aphids until two years from harvest. Larger growers are using tractor-driven airblast mistblowers. For smaller growers, a backpack mistblower is a great alternative.

Many folks have started spraying in the fall for Cinara aphids and balsam woolly adelgid, which frequently results in twig aphid control the following spring. If you aren't one of those people, you will probably need to treat for twig aphids this spring.

Twig aphid control is only important the year of sale and year before sale. There is no need to control twig aphids in younger trees, as the new growth will hide the needle curl. If there is damage and even reduced growth, the trees tend to set extra buds for the following year, and growth will not be slowed down at all. But if it takes 2-3 years to harvest all the trees out of a block, a grower may end up treating 4-5 years in a row for twig aphids.

Traditionally, people treated right before bud break. Since most were using the granular formulation of Di-Syston, this was the a good approach as it was important to wait until all the eggs had hatched. This product is no longer available for use and other products can be applied much earlier in the spring.

The loss of Di-Syston will especially impact the smaller growers who may not have spray equipment. Most larger growers have switched more and more to using tractor-driven airblast mistblowers as the price of Di-Syston increased during recent years. This equipment gets good twig aphid control provided there are enough access roads. Adding a material to the pesticide to increase droplet size is helpful to both reduce drift and get better coverage. Be sure to scout in the middle of the block after April 15 where coverage may have been light to make sure control is adequate. But if you don't have a mistblower, you will need to decide how you will treat in the spring.

A high pressure sprayer is always the best choice for pesticide application as you will get the best coverage. For twig aphid and mite control, it is not necessary to crank up the pressure or use a straight-stream spray pattern as you would with balsam woolly adelgid control. Instead, reduce the pressure, broaden the pattern, and you will find you will get better foliage penetration. Don't try to treat more than 2-4 rows at a time, even in smaller trees. Unfortunately this application method is slow, and smaller growers often can't afford these sprayers. If they hire someone else to spray their trees, and the weather doesn't cooperate, they risk not getting their trees sprayed at all.

If you are a smaller grower, a backpack mistblower may be the answer. This equipment gives enough coverage to control all Fraser fir pests including woolly adelgid. It gives much better coverage than a regular backpack sprayer. There are several lower acreage growers that only use this to apply insecticides. The sprayer is not for the physically weak! It is heavy, but even I can handle it on steep ground. It sprays faster than I can walk, but you can change the settings to reduce spray output. And priced between $600-700, most growers can afford it. You will find you will apply around 50+ gallons of water per acre which means a lot of trips to fill up, so having a nurse tank is helpful.

Whatever equipment you use -- mistblower, backpack mistblower, high pressure sprayer -- be sure to treat trees from opposing directions. Try spraying some trees with plain water to make sure you are getting good coverage. And DON'T TRY TO SPRAY WHEN THE WIND IS MORE THAN 10 MPH or IF IT'S ABOUT TO RAIN. It's just a waste of pesticides, time and effort, and makes the entire industry look bad.

There are many choices in pesticides for spring pest control. I'll go over these in another post. But remember, for many of them you can spray beginning in March -- which is just next week! (Guess we'll have to get rid of the snow first!) Don't wait until the last minute as you never know if the weather will allow you to spray or not.

So You Treated in the Fall...

SUMMARY: If trees were treated in the fall with Talstar or Asana, it may not be necessary to treat in the spring for twig aphids. However, it is important to scout to determine if twig aphids have been controlled, and if there are other pests that need controlling.

Spring will come. I know it doesn't seem like it now, but it will! And one thing that Christmas tree growers need to think about is what to do for insect and mite control in the spring.

What each grower has to do depends on two things: 1. what they treated with for insect control last year and 2. what pests you have in your trees.

What you did last year sets you up for this year. Many growers are treating their market trees in the fall to control Cinara aphids, woollies, and other pests. This is a good way to set up a more problem-free spring. If you did treat last fall, this post is for you! Unfortunately, that doesn't mean you get to be lazy this spring! You still need to scout.

Hopefully if you treated in the fall with either Talstar or Asana, you should have controlled your woollies and Cinaras, your twig aphids for this spring, and not created any problems with rust mites The key word though -- I use these kinds of qualifiers a lot! -- is "SHOULD." Control of none of these pests is guaranteed. Bugs don't read books after all. That's why you need scout come spring.

It doesn't have to be an extensive scout, just a quick look-see. Check on any old woolly trees and see if you can find any live woollies. Beat a few trees to see if any twig aphids are falling out (be use to use your hand lens to make sure you can find the littlest ones). Also pull some shoots and look for rust mites.

You should wait to do this first checking until the twig aphids are close to being fully hatched. Sometime the 1st or 2nd week in April, make your evaluations.

If you don't find anything -- GREAT! Come back again right before bud break and checkagain, just to make sure that twig aphids have been controlled. Remember that these aphids multiply rapidly, so their numbers can quickly build up.

If you found many aphids, you will probably need to treat for twig aphids again -- that is, if they are go-to-market trees that you are concerned about needle curl. Why didn't the fall chemicals work? It might have been an issue with coverage, or not a full enough rate. In any case, it's time to haul out the spray equipment and get busy before bud break.

If you are't finding twig aphids, but you are other pests -- say a few rust mites or spider mites -- the question of treating because a bit harder. These pests have the potential to build in numbers and cause damage -- but the numbers can also crash, resulting in little to no damage. My suggestion would be to keep scouting to see if numbers are increasing or not. If they have reached treatment threshold, a good miticide such as Envidor should give season-long control. If you are seeing these early enough in April, you can also get good control using a 2% horticultural oil solution. Remember that coverage doesn't have to be as good to control rust mites, but it is more of an issue with spider mites.

If you are finding elongate hemlock scale, you can treat in the spring, or you can wait until summer. If all you have to control is scale, I would probably wait until summer. If you are spraying for other pests though, go ahead and add the materials to control scale as well. Control for scale is somewhat reduced in the spring, but some have gotten decent control. I would wait as close to bud break as possible to allow the scales to produce as many crawlers as possible.

Just one scouting trip wouldn't be enough to give me peace of mind. It's important to check again right before bud break. Now if only 1-3 aphids are found, you can feel a bit more safe that twig aphids won't cause much damage. However, if more than a couple of trees have aphids, and you can beat out several, you might need to treat quickly to avoid damage. Once bud break has started, Dimethoate is a good choice to get control.

Scouting takes time, but it's worth it to identify fields where you can avoid making another insecticide application.

Organic Christmas Tree Project

Photo caption: The Extension organic site in June, 2009, a little more than a year after planting.

SUMMARY: In 2008, an extension organic Christmas tree project was started in Alleghany County. Growth has not been as good as normally produced trees at the same site, and costs are higher. It cost $1.50 per tree in materials and labor to put ground cloth around these trees at planting to reduce weed competition. It takes about 8 times as long each year for weed control (weed eater vs. applying low rates of Roundup). The tree terminals in the organic site are about 1/2 as long.

There has been interest in growing Fraser fir for Christmas trees organically for many years in western North Carolina. To my knowledge, there are 2 or 3 certified organic Christmas tree growers in NC that harvest a few hundred to a few thousand every year.

Back in the mid-1990's, several of us in extension did surveys of customers to determine if there was a market for organic Christmas trees. I went to a couple of choose and cut farms (Doug Hundley helped me at the one in Avery County), and Jeff Owen, the area extension specialist with Christmas trees went to an organic grocery store in the Asheville area.

What we found at that time didn't indicate a great demand for organic Christmas trees. Many of the people that Jeff interviewed that were buying organic food either didn't celebrate Christmas or they didn't use Christmas trees. People that I interviewed were interested in integrated pest management as a way of reducing pesticide use, but they were primarily wanted to have a pretty tree at a reasonable price. They didn't indicate that they would pay more for an organic Christmas tree.

However, in the past 15 years, this may have changed as more people are buying organic products. "Green" is definitely in and many people are convinced that organic production is the most environmentally friendly way of producing any crop. I myself prefer organic bananas, carrots and tomatoes because they haven't been loaded down with nitrogen, and therefore, in my opinion, they taste better.

Fraser fir, being a somewhat slow growing and finicky plant, doesn't lend itself to easy organic production. Pest control is really no problem. Even though there are several introduced pests that aren't easy to control (namely the balsam woolly adelgid and elongate hemlock scale) practically all pests can be kept at bay with horticultural oil. And now that there is Saf-T-Side oil without the issues of oil separating out and burning foliage, pest control shouldn't be a problem.

The big problem is weed control. Historically, this has always been the biggest issue with Christmas tree production. Weeds, and especially grasses, will always outgrow conifers. After all, that's why Fraser fir is found at the highest elevations -- because they can grow there and other plants don't. In fact, the top of Mount Mitchell was never logged -- not because Govenor Craig made it a state park and therefore saved it, but because the very top of the mountain was almost entirely Fraser fir. The economically important red spruce was found at slightly lower elevations.

Using low rates of Roundup not only stunts weeds to allow trees to grow, it shifts the ground covers away from grasses to clovers and other low-growing perennials. These living ground covers then become weed control, so that harder to control weeds like poke and ragweed can't get a foothold. That is impossible to reproduce organically without disturbing the soil.

In 2008, several of us started an extension organic project at the farm of one of our county agents, Della Deal. She had a small farm that had just been set in Fraser fir, that she was willing to donate for the project. Also involved were myself, Jeff Owen, Bryan Davis, and Richard Boylan, the alternative agriculture agent in Ashe and Watauga Counties. My goal was to see how much it would cost us to grow a pretty organic Fraser fir Christmas tree. I wasn't interested in an experiment looking at different options for fertility and ground cover management. I wanted to use our best guess as to what would work.

To control weeds, we used an 18 inch square piece of ground cloth that was placed around each tree and secured to the soil with staples, keeping the weeds from growing right up against the tree. Della's field was about 1 acre in size, and we initially had every intention of doing the whole acre organically. But 89 man-hours later, when we were only 1/2 through, we realized that we wouldn't be able to complete the whole project. Necessity being the mother of invention, we decided that the lower half of the field we would call "late organic."

To get organic certification, you can't use unlabeled products for three years. Fraser fir is more than a three year crop. So we decided to handle the trees like a commercial Christmas tree grower would for the first three years, and then switch to organic production for the last three years. We figured between the time in cutting the fabric (it's cheaper to buy it in rolls), putting it around the seedlings, the cost of the fabric and staples, and our labor (we "paid" ourselves $10 per hour), it cost $1.50 per seedling to use the fabric.

Of course we had set up the whole field all wrong. If we had known we were going to be doing this, we would have blocked the field off with a plot of "organic" next to a plot of "late organic" replicated through the entire acre. That isn't what happened. The organic section is at the top of the hill where it is rockier, and has no doubt lead to more issues with seedling mortality.

Our second stumbling block was the weather in 2008. It was DRY. In fact, I'm surprised we lost as few seedlings as we did. There were 6.4% mortality in the organic trees and 3.3% in the "late organic" trees from May to October, 2008. These numbers are not outrageous for newly set trees. Really considering how little water fell that season, the survival was remarkable. I was really worried that the ground cloth would make the soil too hot and cook the little seedlings, but that didn't happen. And if you look at the pattern of mortality in the field, you can see that most of the seedlings died in the organic section where it was rockiest. In the upper-most area where it isn't rocky, we lost almost no seedlings.

Of course, the lack of rain helped with weed control. I was surprised how little it took to control the weeds in the organic section. Bryan used a weed-eater twice in 2008. We have some problem weeds in this field including lots of fescue, spotted knapweed, and poison ivy. Because of the PI, Bryan won't let me help him weed-eat as I am quite allergic to it. (He is probably more worried about me cutting down little trees). .

Spring of 2009, we fertilized the trees with organic fertilizer which we scattered on top of the ground cloth. We were kind of late knocking down all the weeds that spring. Bryan went through with a weed-eater in May, but the trees had already started to grow and they were shaded too much, causing the growth to be stunted and off color. By the way, it typically takes Bryan 4 hours to weed-eat the entire organic plot which is about 1/2 acre. He applies the Roundup (8 ounces per acre) on the "late organic" which is also about 1/2 acre in about 1/2 hour.

On July 21st after the trees had hardened off, Byran and I went through and measured the terminal growth of a random selection of seedlings in both parts of the field. There was tremendous variation, as you always see with Fraser fir. But the seedlings in the "organic" section grew an average of 4.1 inches and the "late organic" an average of 7.4 inches. That's a big difference.

What I've learned so far is the following. First of all, we really didn't set up the field correctly for organic. It probably isn't even the best field to grow organic trees. It faces southwest, which will mean it will be hotter and there will be more problems with spider mites. There was a lot of fescue in the field prior to planting. We didn't put down any organic matter prior to planting. If I had my druthers, I would have incorporated as much organic matter as possible, and tried to kill out the grasses before the trees were ever set. It would have been best to start a year before setting the trees to get the site ready. But when we started, the seedlings were newly planted. You don't look a gift horse in the mouth, so we went with what we had available.

Secondly, we need to be quicker knocking down the weeds in the spring so the young seedlings can grow better. Thirdly, we need to find a better source of fertilizer and think of other ways of putting it out.

I am speaking at the Organic School in Asheville on March 6 & 7. I don't know if anyone will come or not, but I certainly enjoyed pulling together the talk and all the information. I keep posting on this site how things are looking with this project.

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: http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn037.html

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: www.oroagri.com. 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: http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn037.htm

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

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 http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn019.html
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.