How Do You Know When Scale Control Is Working?

It's not always easy knowing if elongate hemlock scale (EHS) controls are working. On Friday, Meghan Baker and I helped a grower evaluate some Safari and Talstar treatments he'd made in July and August. I collected  shoots to look at under the microscope to determine if the scales were alive or dead. That is the only way to know for sure what kind of control you've gotten. Unfortunately, it takes a lot of work, and few people have access to a microscope.

So how can you tell how well your scale controls are working? Here are some things you can look for several months after treatment. Remember, you won't be able to tell within a few weeks. In fact, all of our treatments can take several months to work.

1. It's a lot harder to find the scales after treatment. The grower we were working with really knews his fields. He went to several trees that he knew had a lot of scale on them, and had a hard timing finding any. That's a good sign that controls are working. One suggestion is to tag trees with lots of scale prior to treating so you know where to go back to!
2. There isn't white cotton from the males scales. We were looking on a beautiful day in January. Though the weather was warm, you wouldn't expect to see the white cotton from the male scales yet. That's more of a summer thing. But, if you treated in the spring and were scouting in the summer and didn't see white on the trees, that's a good indication that there has been some control. But, I've seen fields where the control was only marginal where the male production was definitely suppressed. So in my opinion, this is not the best indicator of control.
3. There aren't crawlers. Crawlers and immature scales are yellow. If you scout several months after application and don't see yellow individuals, then it's a good indication that the treatments have worked. 
4. There aren't scales on the newest growth. If you treated last year or in the spring, and you don't see any scales forming on the new growth in June or July, that's a really good indication that controls are working . The scales will remain on older growth even if they are dead. Of course some do fall off, but some will remain. So always look at the newest growth to see if there are any scales forming. This is one of the best indicators of control, but you have to wait for it!
5. The scales look dried up and are falling off. When controls are really good, there is a different appearance to the scales. The males all look dried up, and the females do too. You don't see any yellow immatures. And you can sometimes see on the needle that there used to be a scale present, and there isn't any more. This is a little tricky, because the females scales are brown, and might appear dead. But if you've seen enough treatments, you can develop an eye for what is really dead and what isn't. It helps to train your eye by looking at some of these samples under the microscope.
6. Looking under the microscope. When I evaluate scale control, I pull 2 or 3 needles off of 6 or 7 different shoots. I try to get some older and some younger needles. I take anything sharp like a pin, and gently prick the very top of the scale. The goal is not to stab the scale and the needle, but to pry off the top of the scales's outer covering to find if the scale is still alive inside. Below are some photos of what to look for.

Obviously, this scale is still very active.

A crawler or any small yellow scales indicates controls didn't work.

Is this female alive or dead?

It is dead because it is empty and dried up inside.

This female is alive, and there are eggs present.

The same photo with everything labeled.

Scales on new growth in June show that treatments didn't work.

The Safari and Talstar treatments made in August gave 99% control. What does that mean? That means that out of 100 or more scales that I examined, only one female was still alive. In actuality, the control is probably even greater because there weren't as many scales as there were prior to treatment.

The grower had some other Safari + Talstar treatments where he used the low rate of Safari (4 ounces per 100 gallons vs. 8 ounces/100 gallons). These were giving 94% control. That means I found 2 or 3 live scales. So should he treat again?

I think I would wait until June to see if scales were showing up on the new growth. If they aren't, I would wait until 2013 to treat again. If they are, he would still have a couple of months to make a treatment in 2012.

This grower also had another scale -- pine needle scale. This scale is much easier to control, and all his treatments worked against it. In the photo below, note some of the scales have holes in the middle, indicating that parasitic wasps have attacked them.

These are all pine needle scale and not elongate hemlock scale.

Assessing EHS control isn't easy. If you need help, contact your local county extension agent and I'll be glad to come out and see. Being patient and waiting until June is probably the easiest way to determine control results.

Safari Labeled for Christmas Trees

Safari is now clearly labeled for use on Christmas trees. The following links have information about this material:

• Pesticides Labeled for Use in Christmas Trees in North Carolina
• Safari label
• Supplemental label for Christmas trees
• Safari MSDS 

To date, excellent control of both balsam woolly adelgid and elongate hemlock scale have been obtained through foliar sprays of Safari at 8 ounces/100 gallons using a high pressure sprayer. I'm continuing to look at other methods of application.

Parasitic Wasps on Scale Infested Trees

This photo depicts Frasers set up to see how likely elongate hemlock scale crawlers will come off of cut trees. The yellow sticky cards were used to trap the crawlers. But something more interesting was found. Wasps!

These are predatory wasps, probably Encarsia citrina though I didn't have them positively identified. They are very small. The following photo has both a wasp (on the right) and a crawler (bottom left) on it. You can see the wasp is only a bit larger than the crawler. 

The wasps lay an egg in a scale and it develops inside. When the wasp emerges, it leaves a hole in an otherwise empty scale casing. You can see these sometimes when looking at scales on trees.

I put a photo of a wasp that hadn't emerged yet from inside of a scale on my October 6, 2011 post "Last Treatments." In that post, I made the comment that when you don't add Talstar or Asana to Safari, you see a lot more parasitized scales. 

Interestingly, I only found these wasps on cards put in the two untreated trees. The tree that had been treated in the fall had no wasps in it. That made me curious to see how readily wasps are found on trees following different treatments. I plan on setting up some branches inside a warm location over the next few weeks to see how many wasps appear on sticky cards. Perhaps this can shed some light on how we can control scales without creating conditions for a quick rebound by killing off all of our natural enemies.

These wasps are very small. You would never see them flying around in your trees. But they are giving you free pest control. That's why its so important to only use an insecticide when you really have to. 

Another view of one of the wasps. 

How Well Do Scale Infested Trees Hold Their Needles?

If a tree is infested with scales, will it cause the needles to shed prematurely? Last year I looked quite a bit at this issue, but without a lot of success. Here are links to the previous posts in case you are interested in following this story: 1. Setting up the study; 2. The results. The big problem with last year's study was that the room where I kept the shoots got way too hot, and there were many branches where the needles shattered. This isn't how Fraser fir normally behaves when cut.

So this year I'm trying again. Yesterday Jeff Vance helped me  collect some scale infested branches. I will be comparing needle shed on these to branches from uninfested trees in the same field. We also collected some heavily infested branches from a second field just to see if they fared worse.

I will be monitoring needle shed on this year and last year's growth. Each branch is in its own water container, with the 3-year-old wood in the water. The study is set up at my house so I can keep an eye on them better. I noticed this morning that they are already taking up water!

Small studies like this allow us to look at this issue with a great deal of detail under controlled conditions. But I'm also very interested in hearing your observations. Are you finding that needles shed worse in scale infested trees? If you have any observations, please let me know. Some questions I would like to ask are these:

• Were the trees heavily or lightly infested? 
• Are you selling trees in northern or southern markets?
• Do you see a difference in performance between foliage in wreaths and trees?

Send me an email at: jill_sidebottom@ncsu.edu

As always, let's learn together as we try to live with this new pest.

White Pine Problems

People still have white pines! And this fall, these have been hammered in the northern mountains by what we think is a needle cast.

People started seeing yellowing and browning needles a few weeks ago. Damage typically occurred in the upper portion of the plant but occasionally was all over. Many growers commented that they had been in the field just a few weeks prior to this and saw no problems, even tagging some trees, only to come back later to find major needle loss.

When you look closely, not every needle in a fascicle is affected. Sometimes there are bands of green and yellow tissue on the needles. Many growers also found that only the sheared white pine was affected. We only found one site where there were some unsheared white pines that also had the same symptoms.

When this occurred in 2007, the problem was diagnosed as Bifusella linearus, a needle cast found on white pines. We have sent samples off to look at a positive identification this year. However, it is often hard to diagnose needle casts. There are several fungi associated with white pine needles. And there is also confusion between needle casts and ozone injury on white pine.

Ozone damages plants by making the stomates sluggish. It is typically the fast growing trees and weeds that are affected most by ozone. The USDA website (click here for site) lists the following plants as good indicators of ozone damage along with the damage seen:

• Blackberry, secondary canes (Rabus spp.): Red to purple stipple.
• Black cherry (Prunus serotina): Red to purple stipple, may drop the injured leaves early.
• Common milkweed (Asclepias syriaca): Purple to black stipple, leaves may be chlorotic (yellow).
• Yellow-poplar (Liriodendron tulipifera): Brown stipple, may drop the injured leaves early.
• White ash (Fraxinus americana): Red to brown stipple. Similar injury is also found on green ash

So if you suspect ozone, look at these indicator plants nearby to see if there is also damage. White pines were taken off the indicator list in 1995. If these are not showing symptoms, it is most likely a needle cast.

This is also some question if fertility is playing a role. This time of year calcium deficiency is showing up in Fraser firs and white pines. If you are having extensive problems with needle loss, it might be a good idea to take some soil samples and plant tissue samples to further diagnose the problem.

No matter what is causing this damage, there is probably little a grower can do. One of the main reasons is that the profit margin is so low on white pines that it makes any fungicide treatment unattractive. However, when we get a positive diagnosis, I'll pass along treatment options.

Of course the main question is if the damage will continue to get worse this fall. In falls past it did not, so hopefully what we're seeing right now is the worst of it, and undamaged individuals will remain looking good. The following are some photos I took on Friday.

Banding on the needles

Not every tree is affected and not all the same way.

On this plant, damage only occurs in the upper portion of the plant.

Another shot of banding.

This tree was affected overall.

Last Treatments

I haven't posted anything on my blog for quite awhile. Not because I haven't been busy, I just wanted to get all my results together before doing so. I've been evaluating multiple spring applications of Safari and other materials for elongate hemlock scale control. Since I feel like I should wait 4 months before making evaluations, it has taken quite awhile. I should finish with the spring applied stuff this week, and then I'll compile the results. Maybe I'll even have them by Friday!

However, I did want to let everyone know that I put out my last EHS treatment yesterday. Well, Jeff Vance did actually. We treated trees with Sniper, the new bifenthrin product and a dinotefuran product (active ingredient of Safari). We mixed the products to give the same as 10 oz Talstar per 100 gallons and 8 oz of Safari. Two rows of trees Jeff treated like a woolly spray, and two rows like a twig aphid spray. We used about 1/2 the water the second go round. Those results, I won't have until February!

If this fall treatment controls scales, it would fit in very nicely with production of Fraser fir. With it you would be controlling woollies, twigs, scales, spiders, and Cinaras in go-to-market trees. You have lovely fall weather which is usually drier and cooler (it seemed rather hot to me in that spray suit though!) to do it in. AND, you wouldn't be affecting the predators at all. So that means you won't be creating problems with rust mites come spring, or a resurgence of scales the following year.

What predators are most important for the control of scales? Lady bugs will feed on them, especially the twice-stabbed lady beetle, but also smaller ones. We've also seen lacewing larvae feeding on scales. There are also parasitic wasps that develop inside the scale itself.

I will share one observation I've been making. When people are using just Safari in the spring or summer and not adding a synthetic pyrethroid (esfenvalerate (Asana) or bifenthrin (Talstar, Wisdom, Sniper)) you see a lot more parasitized scales.

In fact, one day I poked open a scale that had a wasp still inside the scale, and when I gently teased it out, it moved it's head around.

Bugs are so cool!

Predatory wasp developing inside female EHS.

This is usually all you see with a scale that has been parasitized. An exit hole!

Clingman's Dome and Wild Trees

Ghostly skeletons of Frasers emerge in the fog on Clingman's Dome as young trees grow around.

I had the opportunity to visit Clingman's Dome in the Great Smoky Mountains National Park this week. It had been years since I'd been there. The last time I visited, it was with Kristine Johnson with the National Park when they were treating for balsam woolly adelgid (BWA). At that time, they used insecticidal soap in the summer to treat the trees around the parking lot, walkway and tower on top of the mountain. To my knowledge, these treatments have stopped.

Treating on Clingman's Dome for BWA in early 90s with insecticidal soap.
The soap was mixed in the white vat and a powerful pump was used to spray the product on the trees.

They would spray the trees with fire hoses using many volunteers.
Hard hats were required as the pressure spray might bring down limbs.

Insecticidal soap isn't the best treatment in the summer as there are eggs present, and many survive the treatment. With soap there are no residuals to kill the crawlers that emerge from the eggs, and it takes about a month for the eggs to hatch. However in the winter when eggs aren't present the road to the top is closed. Also I'm sure there was quite a bit of damage to the natural habitat just from all the spray activity.

Today it looked different than I remembered. There weren't many tall Frasers, but there was quite a bit of healthy regrowth. Still, it looked like there was a lot more open ground than when I was there last.

Shot from the visitor center parking lot at Clingman's Dome on 8/17/11. 

We were there on a very foggy day as can be seen in this video. It is living in the fog that makes Fraser fir such a great Christmas tree. Frasers are very sensitive to dry air since they live in the clouds. They quickly shut their stomates which keep them from drying out.

The following are photographs from the visit.

The tower today. 

Lots of wildflowers are growing in areas left bare from dead trees.

The young trees coming on look good, but they are somewhat resistant to BWA as they produce juvabione.
This is an insect growth regulator that keeps the insect from becoming mature.

Larger trees stop producing juvabione and become infested.
Each white spot covers an adult female which will lay a dozen eggs or so. 

The tree in the previous picture is on the left. It has no top left. Other trees around it still do.
The loss of apical dominance is a symptom of BWA infestation.

Even with the dying trees, Clingman's Dome is a popular destination.
The steep walk to the tower and all the fog doesn't keep people from going to the top,
even if you have to stop to catch your breath along the way!