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:

ENVIRONMENTAL HAZARDS
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.

Horticultural Oil

Now is a great time to apply horticultural oil for control of Fraser fir pests. Horticultural oil is the workhorse of organic pest control of Christmas trees. But even if you aren't growing organic certified trees, it provides a good way to control most pests. It can control balsam woolly adelgid (BWA), balsam twig aphid (BTA), spruce spider mite (SSM), hemlock rust mites (HRM), and elongate hemlock scale (EHS).

Oil burn on needles

How oil works. Oil controls pests by smothering them. Therefore, you have to get complete coverage of the tree so that pests on all surfaces are coated with the oil solution. For pest control, a 2% solution of oil (that is 2 gallons in 100 gallons) is required. At this concentration, however, the tree may be damaged. Needles may turn brown and drop off the tree.

Types of oil. Not all oils are alike. To get the best pest control without foliage burn, use a highly refined horticultural oil. These are often called summer oils. Do not use a dormant oil as these will cause foliage burn. Look for oils with at least 92% unsulfonated residues on the label. But the higher, the better! It will list this value under the active ingredients.

Encapsulated oil -- a new type of oil. There is a new type of oil on the market called Saf-T-Side oil. The encapsulation process results in an oil that mixes with water with water and won't cause burn. This is more expensive than regular oil, but you will not need good agitation in the spray tank.

Applying oil. Typically a high pressure sprayer will give better coverage. If a limited number of trees are being treated, you may also use a backpack mistblower. Treat trees from opposite directions to get the best coverage. If you are controlling BWA, you have to wet the tree all the way to the trunk.

The encapsulated oil can be used with any type of sprayer. Other oils should only be used if there is good agitation in the spray tank. A paddle type agitator is better than by-pass pressure recirculating into the tank because the agitation is continuous. The oil and water can separate in the hose if you stop spraying for awhile, so if you do spray what's in the hose back into the tank to remix the solution.

Twig aphid egg killed by oil

What oils will and will not do. Horticultural oil has no residue. It only kills on contact at the time of application. Control of some pests is excellent, but control of other pests is not as good. However, if oil is used each year, pest numbers will continue to be suppressed.

A 2% solution of oil applied in mid-March will do a good job of controlling the following pests:

• All stages of HRM -- actually oil works as well as expensive miticides when controlling rust mites
• BTA eggs
• SSM eggs
• BWA crawlers, nymphs, and adults though the adults are covered with white wool and are therefore harder to wet.
• Cinara aphids

Control of the following pests is not as good. A 2% solution of oil will only suppress the following:

• BWA eggs – however, there shouldn’t be any BWA eggs present in mid-March
• BTA nymphs or adults. Therefore be sure to treat before the twig aphid eggs start to hatch
• EHS -- this is really too early in the year to get good EHS control. You can treat for this pest in the summer with oil, but problems with burning foliage increase in hot weather.

Be sure to keep scouting through the spring to make sure treatments have worked.

Getting the Most Bang From Your Pesticide Buck

At the North Carolina Christmas Tree Association meeting in Boone on Thursday, March 1, Doug Hundley, Brad Edwards, Brian Davis and I talked about getting the most out of the pesticides you use to control pests in Fraser fir. The following is an outline of what we talked about.

First some updates:

1. The uses of endosulfan (Thionex) are cancelled as of July 31, 2012, so if you have any of this product, use it this spring or dispose of it properly. I blogged about this on June 11, 2010. 
2. Sniper (active ingredient bifenthrin) has a new Christmas tree label. Click here for the Sniper label.
3. Safari (active ingredient dinotefuran) has additional labeling for Christmas trees. Click here for the supplemental Safari label. You need to have this in your possession if you use this product on Christmas trees.  I blogged about this on January 5, 2012. 
4. A combination of Safari and Sniper controls multiple pests. With the Safari, you get elongate hemlock scale (EHS) and balsam woolly adelgid (BWA). From the Sniper you get BWA, spruce spider mite (SSM), balsam twig aphids (BTA), and Cinara aphids. Using this in August to early September provides the best control of most Fraser fir pests without creating more problems with rust mites (HRM) and having the least impact on predators. About the only pest that these will control control are HRM and rosette bud mites (RBM).

Next, what will always be important: 

1. Cultural practices. Using proper cultural practices prevents a lot of pest problems. That's the biggest wheel of the pest control machine. There are many cultural practices that help us with pest control. We mentioned a couple of them at this meeting.
1. Chainsaws. Brad talked about this one. The hardest to control pests like BWA, EHS, and RBM can be partially controlled by cutting out heavily infested trees. Some growers have even harvested a field just using this method of pest control without ever using a pesticide. And even if you do spray, it will help the control last longer because you've gotten rid of a big source of reinfestation. After all, nothing kills 100% of the bugs.
2. Nitrogen. Brian talked about the fields of young trees where they are first seeing EHS were fertilized with 18-46-0. That's because when you're feeding your trees, you are also feeding the pests! With good clover groundcovers, consider skipping nitrogen applications until the trees near harvest.
2. Scouting. Scouting is the steering wheel for the pest control machine. Identify the major pests -- RBM, EHS, and BWA. Then as trees near harvest, keep an eye on aphids and mites. Brian told the story of watching SSM populations crash in trees last summer because it was wet and humid and he was seeing the predatory mites. He ended up not treating thousands of trees because he knew through scouting that natural controls were working.
3. Coverage. The smallest wheel of the pest control machine are pesticides. But if you're going to use them, be sure you don't waste them. Safari is a good systemic. But even with this product, we're finding that the best controls of pests like EHS happen when the grower gets really good coverage.
4. Natural predators. Protect them so they can protect you. We are finding a lot of the EHS parasitic wasp, Encarsia citrina. Lady bugs, lacewings, hover fly larvae, predatory mites -- they are all important. So how do you protect them? 



A great home for predators!

1. Don't use a pesticide unless you have to. Scout first, only treat for what you have. And don't try to overprotect young trees. A few aphids and mites in them won't hurt one bit.
2. Keep your groundcovers going. That provides food for predators and greater biodiversity.
3. Switch to treating in the fall when predators aren't as active.

What are your pest control priorities?

If you have to treat for RBM, you have to treat in a very narrow window. The second priority would be EHS control. If you don't have these but have BWA, then treating in the fall is a great option. And don't worry about aphids and mites until you are nearing harvest. How do you know what your priority is? You scout of course! 

In the next few weeks, I plan on launching a new website that goes over all the treatment options -- pesticides, times of year -- to control all Fraser fir pests. I'll blog about it when it goes public. 

Modified Treatment Wheel

I showed this modified color wheel at the North Carolina Christmas Tree Association meeting in Boone on Thursday, March 1.

We use this wheel to show Christmas tree growers when you can treat for the various pests. Based on what we were seeing last year, I modified the timeline for the elongate hemlock scale. We've been seeing good control from mid May through August. Spraying before bud break and later in September probably won't work as well, though it may fit better into your spray schedule -- hence the dotted pink line. If you don't have twig aphid control in market size trees, you might need to treat before bud break. The fall treatment window in September is better for protecting natural predators as well as Cinara aphid control. We'll continue to evaluate control during those treatment windows in 2012, so if you do treat then, let us know so we can follow how well its been working.

Abandoned Christmas Tree Program

An abandoned Fraser fir Christmas tree field which harbors balsam woolly adelgid.

This past summer, a request was received by the N.C. Natural Resource Conservation Service to begin a a cost share program to clean up fields of abandoned Christmas trees in western North Carolina. The concern of disease and insects building up on these abandoned trees and then moving into plantations that were being cared for was what led to this request. The program has been approved and is now available to landowners in western North Carolina. The following are some of the specifics to the program. For more information or to enroll, you will need to contact your local Soil and Water Conservation office.

Purpose:
Removal of abandoned Christmas trees to reduce sedimentation. An abandoned tree field may consist of trees of any size where interest has been lost to continue standard management practices for production.

Policies:

1. Trees are to be cut to an appropriate level not to exceed 3 inches. All side branches are to be removed.
2. Debris is to be processed onsite by chipping, windrowing, and/or burning as deemed legal by the Division of Air Quality.
3. Offsite processing or disposal costs will not be covered under this BMP.
4. Re-vegetation with grasses, pines, or hadwoods is required.
5. Payments will be based on actual costs per acre not to exceed $500.
6. If a cooperator is going to graze livestock on cost-shared fields, then he/she must provide at his or her own cost livestock exclusion, watering facilities, stream crossing, etc.
7. The abandoned tree field cannot be replanted into Christmas trees within the maintenance period. The BMP is considered out of compliance if the land use changes (due to the replanted trees or grasses) to another use within the maintenance period.

The following Avery Journal article also has information about this program, "New cost-share program to remove abandoned Fraser fir."