Pesticides & Wildlife Christmas Trees

Prepared by:
William E. Palmer, Wildlife Graduate Research Assistant
Peter T. Bromley, Extension Wildlife Specialist
Jill R. Sidebottom, Area Extension Specialist, Forest Resources


Wildlife is an important part of a healthy rural environment. This fact sheet is one of a series that describes how pesticides can be managed to minimize harm to wildlife on our farms, in our waters, and in our forests.

Wildlife is a valuable natural resource. Most Christmas tree growers enjoy seeing wildlife on their farm. Some growers benefit economically by leasing hunting and fishing rights to sportsmen. In North Carolina, more than $1.1 billion is spent annually by hunters and fishermen alone.

Christmas trees provide a good habitat for many species of wildlife. Songbirds nest in Christmas trees and feed insects found in plantations to their young. Birds of prey, foxes, and snakes feed on small mammals that live in the grassy understories of plantations. Game birds, such as wild turkeys and quail, bring their broods into plantations to feed on grasshoppers and other insects in the understory. Deer and rabbits also find food and cover in Christmas tree plantations.

Pesticides used in Christmas tree production can harm wildlife living in or around plantations. The consequences of pesticide exposure to wildlife varies, depending on the toxicity of the pesticide to the animal and the dose the animal receives. If exposure is great enough, the animal will die. Some of the insecticides used on plantations have been shown to cause wildlife sickness or death. Birds made sick by an insecticide have been found to neglect their young, abandon their nests, and become more susceptible to predation and disease. For instance, research has shown that bobwhite quail, once sick, are more vulnerable to "blackhead disease," which is deadly.

Careful selection and use of pesticides, however, can reduce the potential of pesticides adversely affecting wildlife. This publication (1) describes how pesticides used during Christmas tree production can harm wildlife and (2) describes how growers can minimize adverse effects of pesticides on wildlife.

Insecticides

Wildlife are exposed to insecticides when they eat granules or residues on plants or in insects, when insecticides contact their skin or eyes, or when they inhale vapor.

Three main groups of insecticides are used on Christmas trees: organophosphates, organochlorines, and synthetic and natural pyrethroids.

The organophosphate insecticides range from highly toxic to slightly toxic to wildlife. They are typically short-lived in the environment and do not accumulate in the bodies of animals. For that reason, most wildlife deaths associated with organophosphate use have occurred withidn a few days after applying a highly toxic product.

One organochlorine insecticide, lindane, is used on Christmas trees. Unlike the first group, organochlorines tend to accumulate in the fat tissue of animals and stay active longer in the environment. Lindane is highly toxic to some birds and extremely toxic to fish.

The third major group, the synthetic and natural pyrethroids, are only slightly toxic to birds and mammals but very toxic to fish.

Table 1 lists insecticides used in North Carolina in the production of Fraser fir, white pine, Virginia pine, and Eastern redcedar. These insecticides are rated low, moderate, and high, according to their toxicities to wildlife.

The insecticides in Table 1 are listed alphabetically by their common, or generic, names. To find a chemical by its trade (brand) name, locate the trade name in Table 2, find the corresponding common name, and then consult Table 1 for the toxicity rating.

Table 1.  Toxicity of Pesticides Used on Christmas Trees to Birds, Mammals,
and Fish

Pesticide (Brand Name) Birds* Mammals* Fish**
acephate (Orthene M L L azinphos-methyl (Gusathion, Guthion) G G EH biphenthrin (Talstar) L L EH carbaryl (Sevin) L L M chlorpyrifos (Dursban, Lorsban, Killmaster) H L EH cyfluthrin (Tempo) L L EH diazinon (Diazinon, Spectracide, Knox-Out) H*** L H dicofol (Kelthane) H L H dimethoate (Cygon, De-Fend) H*** M M disulfoton (Di-Syston) H H H esfenvalerate (Asana XL) L L EH ethion (Nialate) M M H fenbutatin-oxide (Vendex) L L EH fenitrothion (Sumithion) H*** L M fluvalinate (Mavrik) L L EH insecticidal oil (Summer oil, Volck) L L - isazofos (Triumph) H M EH lindane (Lindane, others) H M EH malathion (Cythion) M L EH oxydemeton-methyl (Metasystox-R) H M L oxythioquinox (Morestan) - L EH permethrin (Atroban, Ambush, Pounce, Pramex) L L EH phosmet (Imidan) L M H pyrethrum (Pyrethrin, Sectrol) L L EH resmethrin (SPB 1382, others) L L EH soap (Insecticidal Soap) L L - trichlorfon (Anton, Dylox, Neguvan, Proxol) H L M
* Wildlife hazard is based on the following toxicities: H (highly toxic) = LD50 less than 30 mg/kg and LC50 less than 500 ppm. M (moderately toxic) = LD50 greater than 30 and less than 100 mg/kg and/or LC50 greater than 500 and less than 1,000 ppm. L (low toxicity) = LD50 greater than 100 mg/kg and LC50 greater than 1,000 ppm. ** Fish 96-hour LC50 toxicities are as follows: EH (extremely toxic) = less than 0.1 ppm H (highly toxic) = 0.1 to 1.0 ppm M (moderately toxic) = 1 to 10 ppm L (low toxicity) = greater than 10 ppm To convert fish toxicities to pounds of active ingredient per acre-foot of water, multiply by 2.7. *** Active ingredient (not necessarily a specific product) has caused wildlife deaths.
Table 2. Trade Names and Common Names of Insecticides Listed in Table 1
Trade Name Common Name
Ambush permethrin Anthon trichlorfon Asana XL esfenvalerate Atroban permethrin Cygon dimethoate Cythion malathion De-Fend dimethoate Di-Syston disulfoton Diazinon diazinon Dipterex trichlorfon Dormant Oil insecticidal oil Dursban chlorpyrifos Dylox trichlorfon Ethion ethion Gusathion azinphos-methyl Guthion azinphos-methyl Imidan phosmet Kelthane dicofol Killmaster chlorpyrifos Knox-Out diazinon Lindane lindane Lorsban chlorpyrifos Mavrik fluvalinate Metasystox-R oxydemeton-methyl Morestan oxythioquinox Neguvan trichlorfon Orthene acephate Pounce permethrin Pramex permethrin Proxol trichlorfon Pyrethrin pyrethrum Resmethrin resmethrin SBP-1382 resmethrin Sectrol pyrethrum Sevin carbaryl Soap insecticidal soap Spectracide diazinon Sumithion fenitrothion Summer Oil insecticidal oil Talstar biphenthrin Tempo cyfluthrin Triumph isazofos Vendex fenbutatin-oxide Volck insecticidal oil
When a pest problem needs to be treated, consult your county Extension Service agent for advice on which products to use. Then consult Table 1 and 2 to choose the least toxic insecticides recommended by the Extension agent. Consider the type of wildlife that are likely to be exposed to each particular application. If birds such as nestlings are likely to be exposed, try to pick an insecticide that has a low toxicity rating for birds. Similarly, if a stream or pond is nearby, use an insecticide having a low toxicity to fish. Remember, as toxicity increases, so does the risk that an insecticide application will harm wildlife.

Granular Insecticides

Granular insecticides present a serious hazard to birds. Disulfoton (Di-Syston 15G) granules are highly toxic and are used to control several insect pests in Fraser fir plantations.

Birds eat insecticide granules exposed on the soil surface, mistaking them for food or grit. To minimize the hazards to birds, it is necessary to incorporate the granules into the soil.

It may be possible to incorporate mechanically in some instances. However, watering down granules as soon as possible (within 48 hours is required by the label) will dissolve granules and eliminate the potential for birds to ingest them. Unfortunately, vapor produced by disulfoton may also harm birds in Christmas trees. In some instances it may be possible to use an insecticide that is less toxic (to applicator and wildlife) and that is formulated as a liquid. Check with your County Extension Service agent for possible liquid formulations recommended for your specific need.

Liquid Insecticides

Many highly toxic liquid insecticides are applied to Christmas trees. A few of these insecticides have been shown to cause wildlife deaths when used to some crops.

To reduce hazard to wildlife from liquid formulations:

Drift can be minimized by using application equipment with low drift characteristics, replacing inappropriate or worn nozzles, using the appropriate pressure and volume for the chosen nozzle, and adding a drift control agent. Also, never spray when the wind is blowing faster than 8 mph.

Pesticides applied with backpack sprayers or low-pressure sprayers are less likely to drift off target than those applied using high-pressure, air-blast sprayers or ultra-low-volume (ULV) sprayers. Ultra-low-volume formulations are more hazardous to fish and wildlife than conventional sprays because ULV sprays often approach 100 percent active ingredient and have a high potential to drift.

Disease Control

Several fungicides are recommended for use on Christmas trees.

Seed beds are treated with metalaxyl (Subdue) and the fumigant methyl bromide. Other fungicides include maneb (Manzate and Manex), benomyl (Benlate), and triadimefon (Bayleton).

Methyl bromide is highly toxic to mammals. It is a restricted use pesticide. However, when applied under plastic to seed beds, it is unlikely to cause significant wildlife problems. Other recommended fungicides are not toxic enough to birds or mammals to be considered a hazard. Benomyl (Benlate), however, is highly toxic to fish.

Herbicides

Herbicides used for weed control in Christmas tree plantations are only slightly toxic to birds and mammals. However, the use of herbicides affect the value of wildlife habitats in plantations. Wildlife benefit from the cover and insect foods that vegetation provides. Also, there are benefits to leaving plant growth between Christmas trees. Leaving some ground cover around trees provides a better environment for mite predators and provides plant and insect foods for wildlife. When white grubs are present in the soil, the use of herbicides for grass control can result in increased grub feeding and damage to the roots of Christmas tree seedlings and transplants. Therefore, maintaining a grass cover by mowing rather than applying herbicides benefits both growers and wildlife.

Rodenticides

Pine voles and meadow voles occasionally damage Christmas tree plantations. Growers can control meadow voles by mowing around trees and between rows. However, when vole infestations are high, rodenticides may be required to reduce damage. Chlorophacinone is safer for wildlife than zinc phosphide. Zinc phosphide is very toxic to birds and mammals and should therefore be avoided. Chlorophacinone is selective to rodents. Hand placement or mechanical broadcasting of pelleted baits is recommended. Refer to the current Pest and Orchard Management Guide for North Carolina Apples (Cooperative Extension Service Publication AG-37) for more details.

Ways to Reduce Pesticide Use

Reducing pesticide use is one of the best ways to protect wildlife resources on your farm. Using sould cultural practices reduces pest problems and results in lower pesticide use. Following integrated pest management (IPM) guidelines can also lead to reduced pesticide use. IPM is a farming approach that employs alternative methods of pest control, rather than relying solely on agrichemicals. With IPM, pesticides are used only when the cost of applying a pesticide is outweighed by the cost of pest damage to the crop. This "threshold" must be reached before chemical pest control is economically justified. In this way, IPM practices help to reduce pesticide use and protect wildlife in the environment. For further information on alternatives to pesticide use, see your county Extension Service agent.

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