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)."

Sunday, April 22, 2012

Celebrate Earth Day with a Christmas Tree

This week while scouting a field for twig aphids and mites, I came across this little nest full of eggs. It reminded me of how Christmas tree fields are home to many creatures -- a perfect reminder of Earth Day.

The most important creatures that tree growers invite into their tree fields are natural predators, brought in when ground covers are managed rather than killed. The next photo is from a field I was also in last week, showing a diversity of flowering ground covers.

That means that tree growers don't have to purchase natural predators like the lady beetles sold here for home gardens. Predators are attracted to the diversity of flowers and insect activity in the ground covers and will feed on any aphids or mites found in the Christmas trees themselves. It's free pest control.

One of the lessons from the Extension organic field in Alleghany County has been that the ground covers that come in when low rates of Roundup are used are far superior to all the grass that grows in the organic trees. After all, we grow grass in our lawns because grass tolerates mowing. Mowing ground covers in the organic trees has promoted grass and actually decreased biodiversity in the ground covers as compared to the lower portion of the field where conventional practices have been used up until this year. In this photo, you can clearly see the line where the clover stops and the grass starts. That's the line between the trees that have been grown organically since 2008 and those that are switching to organic production this year. Mowing promotes grass and it has certainly taken over to the detriment of the trees and the natural predators as well. (For those wanting to grow Fraser fir organically, it will be important to plant clover and other beneficial ground covers in a field the year before the Christmas trees are set -- something that wasn't done on this site. But that's for another blog entry!)

These ground covers, however, are also forage for bees. Clover, wild mustard, and purple deadnettle especially bring the bees in. Protecting bees can be as simple as choosing the time of day when you spray with an insecticide. Spraying trees in the late afternoon or at night for mistblower operators, is a good way to avoid problems with bees. Switching pest control to the fall is also a good way to avoid problems with bees. Be aware if someone has a commercial or even a hobby hive near your tree field. For fields close to bee hives, a mid-March application of horticultural oil will control most Fraser fir pests without causing a problem with bees at all.

April 22 -- Earth Day -- might seem like an odd time to think about Christmas trees. But those involved in the Christmas tree industry in western North Carolina know that every day is Earth Day in a Christmas tree farm!

Friday, April 20, 2012

Strange Spring: The Continuing Saga!

This spring continues to be unique. I was in a field in Avery County at a fairly high elevation yesterday, and one in Transylvania County at a low elevation today, and bud break was about the same. Only a few trees had broken a few buds in both fields, but it looks like the trees are ready to pop. I think the cooler weather this week has slowed things down.

But don't expect the cooler weather to slow the bugs down. The twig aphids are reproducing. This typically happens right before bud break, and they are doing the same again this year. The difference is that it appears that bud break and perhaps shoot growth might take longer than normal. That means that the trees will be at their most vulnerable to twig aphid attack for a longer period of time. Also, the warm spring has allowed for good aphid survival and reproduction. It all adds up to a potentially bad year for twig aphids.

That is why I've always warned people that if you are beating the foliage and finding even a few aphids, they will reproduce and end up being a problem. Each female aphid can produce 10 to 15 live young -- making what you saw last week 10 times more this week.

Rust mites are also quite active and will remain so until temperatures really warm up.

The good news is there has also been a lot of rain, which will help the trees grow out of any twig aphid damage. The following aren't very good photos, but they illustrate my point. The first picture is of a tree with twig aphid damage in May. The second is of the same tree in July. Most of the damage has straightened back out.

Shoots actively growing show lots of needle curl...

... but the mature growth has little damage.
So don't get too concerned with twig aphids. Use your judgement. Still, it's a good idea to recheck the trees that you plan on cutting this year that are your best trees, and treat them if necessary. Dimethoate is a good choice at this point as it will penetrate the cones and any broken buds. However, remember that Dimethoate is quite toxic, and is especially a problem when bees are active (which they are now in ground covers). Consider spraying later in the day, or if you are using a mistblower, of an evening.

With as much wind as we've been having this spring, I know how hard its been to get sprays out. Just remember, that poor conditions for spraying will give poor control results. There's little need to waste time, money, and put the environment to risk by forcing a spray job under windy conditions.

Let me know if you have any questions, and good luck!

Monday, April 16, 2012

Who Can Learn to Scout?

ANSWER: Anyone!

Yesterday, Brad Edwards showed a picture of his girls scouting for pests. His 6-year-old was identifying twig aphids and elongate hemlock scale, and showing the grower what to look for and what to do. I love it! Way to go girls!!!

Sunday, April 15, 2012

The Early Spring: A Message From Doug Hundley

Doug Hundley, Avery County IPM Technician, sent out this message to his IPM folks. I thought it was so good, I've copied it here for everyone.

The only other thing I would add to this is the need to be aware of bees in the field when you spray. Don't apply products like Dimethoate when bees are actively foraging. I posted something about this a couple of weeks ago in: Bee Careful, but it bears repeating.

Doug Hundley (left), talking with Brad and Scott about scales.
Good day everyone,

How early the Fraser budbreak will be this year will obviously be a record breaker; like everything else that is happening this spring.  This is hardly news worthy now.  The frost events this last week were, of course,  tough on the fruit and flowers but we lucked out on the Fraser buds in Avery County.  Below 3,000 ft.elevation, light damage may have occurred.

Today I wanted to know if you are seeing what I am seeing out there.  The cones have emerged and have made a good hiding spot for any BTA in the trees.  As you know, from this point on, any BTA treatments need to include Dimethoate and be applied with a high pressure hose sprayer.  The cones should be targeted specifically to get adequate penetration.  Of course if you have the time to remove the cones and carry them out of the field, a mistblower application could work for a few more days.

I said a few more days because it looks to me like the new growth buds will be breaking this week.  Budbreak is already underway below 3,000 ft. ; elevation in locations like Mountain City.  As the buds emerge, hose applications that include Dimethoate will continue to be somewhat effective for about 2 weeks into budbreak.  After that, we have no other options.  I know some of you are adding Safari to your spring BTA treatments.  We really need to know how well Safari works in April and letting us know when and where you are treating with Safari will help very much.  Please respond via email and we'll monitor your results over the summer.  Thanks in advance!

The high winds and early budbreak have made it another tough year to treat for BTA in the springtime.  I know many of you are enjoying the benefits of having made your BTA treatment last summer or fall.  What a great development this has been.  However, if you haven't already heard, that Hemlock Rust Mites are having a very good year.  The rust mites have enjoyed this perpetual spring that began in January.  With temperatures forecasted to top out in the 60's for the next 7-10 days, we don't expect the rust mites to do anything but increase. 

I know that many of you have been treating for BTA in the Fall for several years and have a sense of security that it always works, which it usually does.  However, never forget the Rust Mites, especially if you applied Wisdom or Asana last year between the months of April and July.  I've seen not only 25 mites per needle but damage beginning to show on the foliage. 

Everything is happening early this year.  That may include Rust mite and spider mite damage as well.  Despite our successful spray programs there is always an important need to scout.  Please reply to me with your own observations.  Feedback from you guys has been very helpful and always will be.

Sincerely,  Doug

Again, thanks Doug for your observations and recommendations. And Bee Careful out there! This spring certainly has been challenging, but if we keep getting rain, don't worry too much about twig aphids! I'd worry more about rust mites!

Wednesday, April 11, 2012

Hemlock Rust Mites Early This Year

The HRM is certainly enjoying this spring. This morning I found a field that had rust mite damage already on 2011 growth. Doug Hundley said he saw some rust mite damage last week. Folks, that's really early! So, be sure to scout for mites this spring.

Remember that Dimethoate will control rust mites, but not the eggs. Envidor and Sanmite control both rust mites and spider mites -- all stages. Horticultural oil and sulfur give excellent control of rust mites. Oil will give pretty good control of spider mites too if you have good coverage. Apollo and Savey do not control any stage of rust mite -- not the egg and not the mites. They are only effective against spider mites. The same is true, of course, of Talstar (bifenthrin).

And no, don't expect this cold snap to slow rust mites down. Only hot weather weather does that! And even though it's been warm lately, it still gets cold at night. Perfect rust mite weatheer.

The following are some photos I took this morning.

This shoot already has bronzing from the rust mites. Compare it's color
to the greener needles around it.
Jeff Vance easily knocked off damaged needles from the 2011 growth.
My Samsung Android amazes me sometimes. I took this photo with my phone.
You can actually see the rust mites on the needle.

Safari Control of HWA

In February 2011 when this photo was taken, these trees had no HWA.
In June of 2010, I made a post on some hemlocks at my office that I had treated for HWA. (See post: HWA Control).

I looked at those trees today and they are covered with HWA and with EHS. The controls worked for 3 years, which wasn't bad.

It seems to me like there is a lot of HWA this spring -- not just on these trees but everywhere. It might be because of the warm winter.

Has anyone else observed how long Safari has controlled HWA? If so, make a comment about your situation.

Tuesday, April 3, 2012

Bee Careful!

Though this picture is of a bee in clover, there are many other flowering
plants in Christmas trees that bees may be attracted to.
Christmas tree pests are very active this spring, and growers are finding they need to treat for mites and for twig aphids. Thanks to chemical mowing, Christmas tree fields are full of flowering ground covers, especially wild mustard and purple deadnettle. These are favorites for bees. That's great for wildlife and biodiversity, but it presents a problem when trees need to be treated with an insecticide.

I wrote the following article for LIMBS & NEEDLES in 2008 with the help of Dr. David Tarpy at NCSU. The information is still appropriate. It gives good information on how to protect the bees that are in your Christmas trees. Basically, the best way to do this is to avoid spraying when bees are actively foraging. Target treatments of an evening or night.

There were several products we use today that weren't mentioned in the article because they weren't used at the time this was written.

  • Safari (dinotefuran) is highly toxic to bees.
  •  Movento (spirotetramat) is not toxic to the adult bees, but if it is taken back to the hive, it will affect how the bee larvae develop. 
  • Envidor (spirodiclofen) is slightly toxic to bees and may cause a problem in contaminated pollen and nectar. 
  • None of these products should be sprayed in areas where bees are actively foraging.

Bees and Trees -- LIMBS & NEEDLES article from 2008

By Jill R. Sidebottom, North Carolina State University

We have lots of clover in our Christmas tree fields now. That’s great news. Clover adds nitrogen to the soil and reduces erosion. It also provides forage for bees. That’s a wonderful thing – most of the time. However, when a Christmas tree grower needs to apply an insecticide, having bees actively foraging in the field can present a problem.

Being insects, it is perhaps not surprising that most insecticides are toxic to bees. Even some organic insecticides will kill bees. The wrong pesticide, applied at the wrong time, will not only kill the bees foraging at the site but can be carried back and kill the entire colony. The good news is that pesticide poisoning of honey bees can usually be kept to a minimum if beekeepers and pesticide applicators take certain precautions.

Most pesticide labels have a special warning about bees and other beneficial arthropods. For example, the label from Dimethoate reads as follows:

This pesticide is highly toxic to bees exposed to direct
treatment or residues on blooming crops or weeds. Do
not apply this product or allow it to drift to blooming crops
or weeds if bees are visiting the treatment area.

This language clearly places the responsibility for the safe use of this pesticide squarely on the applicator. Beekeepers can help applicators by making them aware of their hive locations, covering their hives with wet burlap, or even moving the hives during times of pesticide exposure. But the responsibility ultimately falls back on the pesticide applicator to make sure that bees are kept safe.

In the NCSU beekeepers notes, “Reducing the Risk of Pesticide Poisoning to Honey Bees”  contains a table with different pesticides and their relative toxicity to honey bees. I have reproduced the tables, in part, showing the materials that are used in western North Carolina on Christmas trees.

GROUP 1 – HIGHLY TOXIC. Severe bee losses may be expected if the following pesticides are used when bees are present, or if the product is applied near beehives or within a day after application to foraging bees in the pesticide application area.

  • Abamectin
  • Acephate (Orthene)
  • Carbaryl (Sevin)
  • Chlorpyrifos (Lorsban)
  • Dimethoate
  • Imidacloprid (Provado, Merit)
  • Malathion
  • Permethrin (Astro)
  • Spinosad
  • Thimethoxam (Flagship)
 GROUP 2 – MODERATELY TOXIC. These pesticides can be used in the vicinity of bees IF dosage, timing, and method of application are correct; but these products should never be applied directly on bees in the field or at the colony location (apiaries).

  • Bifenazate (Floramite)
  • Disulfoton (Di-Syston)
  • Endosulfan (Thiodan)
  • Fluvalinate (Mavrik)
 GROUP 3 – RELATIVELY NONTOXIC. These pesticides can be used around bees with a minimum of injury if the dosage, timing, and method of application are correct. Never apply pesticide directly to the beehive.

  • Diflubenzuron (Dimilin)
  • Esfenvalerate (Asana)
  • Pymetrozine (Endeavor)
If the pesticide you are interested in is not listed here, you can sometimes find the LD50’s for bees under the MSDS (Material Safety Data Sheets). A material is considered ‘highly toxic’ if the LD50 is less than 2 µg (microgram or 1/1,000.000 of a gram) per bee. It is ‘moderately toxic’ if the LD50 is 2 to 10.99 µg per bee; ‘slightly toxic’ if it is from 11 to 100 µg per bee; and ‘practically non-toxic’ if it is from 50 to 100 µg per bee. For instance, the contact LD50 for bifenthrin (Talstar) is reported as 0.01462 µg/bee, which would make it highly toxic.

The LD50’s for bees can be somewhat misleading, though, because they express the pesticide toxicity to the individual bee. A product that is moderately toxic but that is applied in a form that is similar to pollen and is collected and concentrated along with the pollen can kill the entire colony.

On the other hand, highly toxic materials may cause less of a problem if bees are not actively foraging in the area. Be sure to check fields the day before spraying to determine if bees are actively foraging. For instance this summer, some of the clover flowers are drying up because of the drought, and bees are no longer present. Also, if materials are applied in the late afternoon (after 3 pm) or even at night, the impact on bees will be reduced. Some growers have successfully used Dimethoate, for instance, near hives if the material is applied in the late evening and is dried before the bees start foraging the next day.

Reducing drift is also important in reducing the likelihood that the material contacts beehives. Air-blast sprayers are more dangerous than pressurized-pump sprayers. If a pesticide application is being made by air, then it is the contractor’s responsibility to notify any beekeepers that have “registered” apiaries (one or more hives of bees) within 2 miles of the area to be aerially sprayed. These regulations are defined in the N.C. Pesticide Laws and the person responsible for the notification is the person who contracts for the aerial application.

More information of bees can be found at the apicultureprogram at NCSU. Another important link is to the North Carolina State Beekeeper’s Association. This is a good place to look at see if the county you have Christmas trees in has a beekeepers association that you can contact about the local of hives near your Christmas tree fields. Finally, you can contact the NCDA&CS ApiaryInspection Service for official apiary records and registration.

The NCCTA is currently advertising the environmental benefits of Christmas trees. If bee kills are associated with Christmas tree production, however, it will be hard to defend such a claim.

Special thanks to David Tarpy, Associate Professor and Extension Apicolturist, NCSU, for helping review this article.