Just how many pesticides are used to produce a single Christmas tree?

Based on the Pest Management Survey described below, on the average it takes 1/4 of an ounce of pesticides over the life of the tree to produce it in the field which is based on the active ingredient in the pesticides including herbicides, insecticides and fungicides used for an 8-year rotation. This value is for Fraser fir production in western North Carolina only. Other areas of the country produce different species of trees with different pest problems. The value is estimated based on a 2006 survey described below and will continue to change as Christmas tree growers continue to reduce their dependence on pesticides. It is a far cry from one recent national news report that erroneously stated it took as much as 28 pounds of pesticides to produce a single Christmas tree. To learn which materials are used and why, please read farther.

What are the pesticides used to grow Christmas trees?

Information on pesticides used in the Christmas tree industry in western North Carolina are based on three pest management control surveys conducted among Christmas tree growers. The first, conducted in 1995 by Dr. Steve Toth, Pesticide Impact Specialist with North Carolina State University, surveyed growers about their 1994 pest control use. The second and third, conducted in 2001 and 2007 by Dr. Jill Sidebottom, Mountain Conifer Integrated Pest Management Specialist with the North Carolina Cooperative Extension Service, surveyed growers about their pest control practices in 2000 and 2006. In the first survey, the 294 growers responding produced 6,660 acres. There were 336 growers producing 14,747 acres that filled out the 2001 Pest Management Survey, and 352 growing producing 22,249 acres who filled out the 80-question 2007 Pest Management Survey. Therefore, these surveys were representative of the industry.

The following tables summarize the results, listing the pesticides that are used on at least 5% of the Christmas tree acreage in 2006. Please note that pesticide usage continues to change and these numbers do not reflect current usage. The industry will be surveyed again in 2014 about 2013 practices.

Though accurate numbers are not available, several trends are worth noting. Thiodan is no longer legal to use in Christmas trees as of July 2012 though it is still being used in other commodities grown in the mountains such as pumpkins. Di-Syston is no longer being manufactured and as stocks of the material are used up, its use will cease. Talstar use continues to increase and a similar product with the same active ingredient, Sniper, is also being used. A new miticide, Envidor, gains popularity among growers as well as Safari, an insecticide used to control elongate hemlock scale.

Insecticides/Miticides

Insecticide/miticide	Percentage of acreage treated in 1994	Percentage of acreage treated in 2000	Percentage of acreage treated in 2006
Di-Syston 15 G	64.6 %	49.6 %	31.9%
Lindane	21.7 %	23.8 %	1.9%
Dimethoate	2.3 %	21.2 %	34.7%
Asana	11.8 %	16.6 %	13.3%
Lorsban	5.8 %	8.4 %	4.6%
Savey	---	5.4 %	3.0%
Morestan	14.3 %	3.0 %	0.0%
Talstar	0.0%	0.3%	11.9%
Thiodan	0.0%	2.2%	6.3%

Herbicides

Herbicide	Percentage of acreage treated in 1994	Percentage of acreage treated in 2000	Percentage of acreage treated in 2006
Roundup	93.7%	94.9 %	89.6%
Simazine	72.2 %	38.8%	16.8%
Goal	43.8 %	20.7%	10.7%
Vantage	23.9 %	14.7%	10.7%
Stinger	22.8 %	11.7%	5.8%
Garlon	---	7.8%	6.1%
Crossbow	0.9 %	3.1 %	5.0%

More information on these most widely used pesticides can be found at EXTOXNET, the EXtension TOXicology NETwork: http://ace.ace.orst.edu/info/extoxnet/

Asana	http://ace.ace.orst.edu/info/extoxnet/pips/esfenval.htm
Dimethoate	http://ace.ace.orst.edu/info/extoxnet/pips/dimethoa.htm
Di-Syston 15 G	http://ace.ace.orst.edu/info/extoxnet/pips/disulfot.htm
Lindane	http://ace.ace.orst.edu/info/extoxnet/pips/lindane.htm
Lorsban	http://ace.ace.orst.edu/info/extoxnet/pips/chlorpyr.htm
Roundup	http://ace.ace.orst.edu/info/extoxnet/pips/glyphosa.htm
Simazine	http://ace.ace.orst.edu/info/extoxnet/pips/simazine.htm
Vantage	http://ace.ace.orst.edu/info/extoxnet/pips/sethoxyd.htm
Talstar	http://ace.ace.orst.edu/info/extoxnet/pips/bifenthr.htm
Thiodan	http://ace.ace.orst.edu/info/extoxnet/pips/endosulf.htm

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Why are they used? What pests do they control? Are they really necessary?

The insecticides and miticides are used to control the following pests in Fraser fir Christmas trees. Most of these pests cause cosmetic damage to the tree, reducing the grade and therefore the value. Heavy damage from these pests can make trees unsaleable for that year. The grower may sell the trees the following year, but only after incurring additional production costs. One pest, the balsam woolly adelgid is not native to the US. Fraser fir is particularly sensitive to it and will be killed. If damage from these pests weren't prevented, it would be impossible to grow good quality Fraser fir Christmas trees. Of all the fir species grown in the United States and Canada, Fraser fir is most susceptible to all these pests.

Elongate Hemlock Scale (Fiorinia externa). You wouldn't think that a pest on hemlocks could cause such a problem on Fraser fir, but it does. The elongate hemlock scale (EHS) attacks many species of conifers. Native to the Orient, it has swept through Fraser fir production areas in western NC in the last 10 years, becoming the number one pest problem. The scale is always on the underside of the needle. But when the white colored male becomes active, it produces a white, woolly covering almost like the balsam woolly adelgid (see below). This ends up on the top side of the needles, making the tree look white. Left untreated the scale causes the needles to turn yellow and drop off. There is also a concern when shipping trees into other areas which are currently don't have EHS. No one wants to spread another problem pest.

Balsam Woolly Adelgids (Adelges piceae). Most pests of Christmas trees cause cosmetic damage. The balsam woolly adelgids (BWA) are tiny, soft-bodied insects that appear as white, woolly spots on Fraser fir. The BWA will kill Fraser fir if left untreated. This adelgid is native to silver fir of central Europe, and was introduced to this continent before 1900. This pest moved into the southern Appalachians in the 1950's and has caused the destruction of the Fraser fir in the natural stands. There are no native predators of the BWA found in the US that specifically attack this pest.

These adelgids are very small and difficult to see. It takes several months for trees to develop symptoms of insect damage. Because of this, the number of adelgids can increase unnoticed and cause serious losses for unsuspecting growers. Luckily, adelgids take a year or more to spread to many trees, so through careful scouting and conscientious control, serious losses can be avoided. Infested trees must be sprayed as soon as adelgids are observed with a high-pressure sprayer. The primary symptom of balsam woolly adelgid attack is a flat top or weak leader. Other symptoms include dead shoots or branches, swelling around the shoot nodes (gouting), reduced shoot growth, a stiff trunk, and growth rings with red, hard wood instead of the healthy, creamy white wood (observed when trees are cut).

Treating for the balsam woolly adelgid is the most costly of all insecticide treatments. A two-man crew using a high pressure sprayer can only treat 1 to 2 acres a day. Growers used lindane in the past to control this pest, but this is no longer manufactured. Now growers are using Asana, Thiodan, Astro or Talstar to control the woolly adelgid. Most growers try to treat only once or perhaps twice in a 5 to 10 year rotation. (A rotation in the time from planting in the field until the Christmas tree is harvested). When people have untreated Fraser fir in their yards, this will increase the presence of this insect and require neighboring Christmas tree growers to treat more.

For more information on the balsam woolly adelgid see Christmas Tree Note 020. http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn020.html
PDF CTN 020: http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn020.pdf

Balsam Twig Aphids (Mindarus abietinus). Balsam twig aphids are small, pale green aphids that feed on fir and spruce trees in the spring. Feeding on the new growth of Fraser fir often results in permanently curled needles. Heavy infestations can also stunt growth. Trees to be harvested in the fall can be made unsaleable by heavy BTA damage.

This aphid is common in western North Carolina and can cause severe damage. It is currently recommended that Fraser fir Christmas trees should be treated the last two years before sale. In the past, most growers used Di-Syston to control twig aphids in the spring. Now most controls are either in the spring or fall with Talstar or other insecticides.

For more information on twig aphids see Christmas Tree Note 019 . http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/CTN-019.html
PDF CTN 019: http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn019.pdf

Spruce Spider Mites (Oligonychus ununguis). These mites are tiny, soft-bodied pests that suck sap from the needles of conifers. Spider mite-infested needles first appear off-color from a distance, and speckled or stippled when viewed closely. As the number of mites increases, the damaged needles can become rusty, bronze, or brown in color by late summer or early fall. In addition, webbing produced by the mites is visible on the needles of heavily infested trees. Heavily damaged needles drop prematurely. Damage is permanent.

With more growers leaving ground covers around trees, spider mites are much less of a problem. Most growers control spider mites where needed with the miticide Envidor or with Talstar.

For more information on spider mites see Christmas Tree Note 029. http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn029.html
PDF CTN 029: http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn029.pdf

Rust Mites(Nalepella spp.). Rust mites are eriophyid mites, a group of tiny, elongated mites with four legs instead of eight, that require a hand lens or microscope to see. They feed on the needles of several conifers including white pine, Fraser fir and hemlocks. On white pine, they cause the needles to turn brown and die. Damage is usually confined to an area on the upper southeast portion of the tree. On Fraser fir, damaged needles appear bronze or rust colored, and may be on one side of the tree or throughout the tree. Damaged needles often shed prematurely. Rust mites are more common during long, warm springs and often disappear in the summer. Trees should be scouted to determine if treatment is necessary. Growers commonly use Envidor or dimethoate to control rust mites.

For more information on rust mites see Christmas Tree Note 034.
http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn034.html
PDF CTN 034:http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn034.pdf

Rosette Bud Mites (Tricetacus spp.). Rosette buds are deformed buds on Fraser fir. They are larger than normal buds and are rounded instead of pointed. Rosette buds usually do not break in the spring. If they do break and develop, they form multiple, weakened shoots. If many rosette buds are found on a tree, the tree develops holes in the canopy, especially if the tree is young when first affected. This decreases the quality and marketability of the tree.

Rosette buds are more common at higher elevations and in specific counties of western North Carolina. Rosette buds are caused by an eriophyid mite similar to rust mites except that it produces a gall, in which it lives throughout the year, where the bud should be. Growers use dimethoate to control rosette bud mites. Typically the grower will only need to treat once in a rotation to control this pest well enough to produce a quality Christmas tree.

For more information on rosette bud mites mites see Christmas Tree Note 018A.
http://www.ces.ncsu.edu/fletcher/programs/xmas/ctnotes/ctn018A.html
PDF CTN 018A: http://www.ces.ncsu.edu//fletcher/programs/xmas/ctnotes/ctn018a.pdf

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How do growers know if they need to apply a pesticide? What else do they do to control pests besides pesticides?

Growers are encouraged to use Integrated Pest Management (IPM) to control pests. Integrated pest management is a system of pest control methods that uses appropriate cultural practices and pesticide selection to reduce pest problems. Scouting is key to IPM.

Most pests of Christmas trees can cause considerable damage if left untreated. However, applying pesticides without prior knowledge of pest numbers in a field wastes pesticides, is harmful to the environment, and can actually cause outbreaks of secondary pest problems. Therefore, scouting fields on a regular basis to estimate pest numbers is imperative. Growers must use a handlens and tree symptoms to find pests in the field. Scouting occurs on a regular schedule with multiple trips to the field. In the 2007 Pest Management Survey, 71.5% of growers thought they scouted more than they did five years ago.

Other IPM practices that growers use to combat pests include: site selection, early harvesting of damaged trees, proper shearing and fertility practices, encouraging natural predators by keeping ground covers around trees and the carefully selection of pesticides, and not interplanting young trees among older trees (pests get on the smaller trees sooner than they would have).

All growers use at least some IPM methods. However, everyone can improve. That's why the NCCES county agents continue to work with growers to help them do things better and safer.

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Why do they have to use herbicides? Why can't they just mow?

Growers prefer using herbicides to mowing or using a weedeater for several reasons. From the grower's point of view, it's quicker and cheaper to apply a herbicide than to mow. However, it's also better - both for the tree and for the environment. Mowing and weed eating can damage the bottom limbs on trees and even kill trees if the trunk is girdled. Mowing also encourages grasses to grow, which can choke out trees or grow up into the tree making weak bottoms. However, mowing is also less environmentally friendly because of the gasoline and oil required to run them. Most herbicides are applied with backpack sprayers which are pumped manually.

Many growers use a technique called "weed suppression." Originally developed at North Carolina State University by Dr. Walt Skroch and others, weed suppression uses lower than labeled rates of herbicides to stunt rather than kill weeds.

For instance, Roundup is labeled at 32 to 160 ounces formulation per acre. Growers use rates of 4 to 8 ounces per acre to stunt the weeds so that they don't grow too tall. This treatment lasts 4 to 6 weeks before another application is required. Growers may treat two or three times through the growing season with Roundup at low rates, then come back in the fall and treat problem weeds such as briars and poison ivy at the full rate to eliminate these weeds.

This type of ground cover management results in a shift of common ground covers away from grasses which are competitive to the tree to small woodland perennials that aren't killed by low rates of Roundup. Clover is a common groundcover that fills in the places between trees with this type of management practice, as are dandelions, nimblewill, wood sorrel, and violets. Clover and bird's foot trefoil are also being sowed by growers in cleared land or other sites where appropriate ground covers are not present; these are then managed further through weed suppression with Roundup.

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Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent.

Environment FAQ's Home | Pesticides Used in Christmas Trees | Health Concerns about Pesticide Use
Pesticide Application | Environmental Impacts

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Prepared by Jill Sidebottom, Ph.D.
Area Extension Forestry Specialist, Mountain Conifer IPM
NCSU College of Natural Resources
NC Cooperative Extension Service

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Mountain Horticultural Crops Research & Extension Center
455 Research Drive
Mills River, NC 28759
Phone: 828.684.3562 ~ Fax: 828.684.8715
Email: jill_sidebottom@ncsu.edu

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Web Crafter: Anne S. Napier and Jill R. Sidebottom
Email: jill_sidebottom@ncsu.edu

Updated August 12, 2012