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.