Pesticides & Wildlife-Tobacco

Prepared by:
William E. Palmer, Wildlife Research Assistant
Peter T. Bromley, Extension Wildlife Specialist
Sterling P. Southern, Extension Entomologist

Dated 2/92
Placed on the Web 3/95 by the Department of Entomology, NCSU


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 farmers enjoy seeing wildlife on their farm, and many 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.

Tobacco fields provide both food and cover for wildlife. For example, quail and other birds nest in grassy strips alongside tobacco fields. Farm wildlife such as these are often called "edge species" because they live in noncrop areas such as hedgerows or along the edges of fields. Wildlife that live in these areas find food and grit in the adjacent crop fields. Pesticides applied to the fields are therefore likely to affect wildlife. For example, researchers tested quail that had been killed by hunters and found that 60 percent of the quail had insecticides in their bodies.

Wildlife that are directly exposed to toxic pesticides can get sick or die. In a 1978 study of quail living near fields that had been sprayed with methyl parathion, 35 percent had enough insecticide in their bodies to cause sickness or death. Birds made sick by insecticides may neglect their young, abandon their nests, and become more susceptible to predators and disease.

While direct poisoning from toxic pesticides is a concern, many pesticides that are not highly toxic can still be harmful to wildlife by reducing the food and cover that wildlife need in order to survive. Insecticides reduce insect foods, and herbicides decrease plant cover. Herbicide use can reduce gamebird populations on farms by disrupting habitats that chicks use to find insects and other foods. Similarly, pesticides can decrease the number of aquatic foods necessary to the survival of ducklings.

Careful selection and use of pesticides, however, can lessen their impact upon wildlife. This publication (1) describes how pesticides used on tobacco fields can harm wildlife and (2) describes how farmers can minimize adverse effects of pesticides on wildlife.

Insecticides

Wildlife are exposed to insecticides when they eat granules or residues on plants and in insects. For instance, quail chicks feed on dead and dying insects following applications of insecticides. Wildlife entering tobacco fields during or soon after an insecticide has been sprayed may be exposed when the pesticide contacts their skin and eyes or when they inhale the vapor.

Exposure to highly toxic insecticides (mainly organophosphate and carbamate insecticides) can result in death of the animal. Sublethal exposure may cause sickness. Birds made sick by insecticides are more susceptible to predation, disease, and exposure. Birds exposed to organophosphate insecticides have been found to neglect their young or even abandon their nests.

Insecticides used on tobacco range from nontoxic to extremely toxic to wildlife. Many soil-applied insecticides are especially hazardous to wildlife; they include carbofuran (Furadan), aldicarb (Temik), fenamiphos (Nemacur), disulfoton (Di-Syston), and ethoprop (Mocap). All of these insecticides are extremely toxic to birds and have caused wildlife deaths.

Tables 1 and 2 list insecticides recommended in the North Carolina Agricultural Chemicals Manual for use on soybeans. Table 1 rates insecticides according to their toxicities to birds, mammals, and fish. The effects of insecticides on wildlife and fish can be minimized by using the least toxic alternative. Insecticides in Table 2 are rated low, moderate, or high based on the hazard their use presents to wildlife (birds and mammals). The hazard of an insecticide is based on its toxicity to wildlife, the way it is used, and other characteristics, such as its persistence in the environment. For example, methomyl (Lannate) is acutely toxic to birds and mammals (Table 1). However, because methomyl does not persist in the field, careful use of this chemical presents only a moderate hazard to wildlife (Table 2). Wildlife exposed to insecticides rated high may die or become sick. Insecticides rated moderate may also cause death or sickness, although death is unlikely. Insecticides rated low are unlikely to harm wildlife directly.

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

Pesticide (Brand Name) Birds* Mammals* Fish**
acephate (Orthene) M L L aldicarb (Temik) H*** H EH carbaryl (Sevin) L L M carbofuran (Furadan) H*** H H chlorpyrifos (Lorsban) H L EH diazinon (Diazinon) H*** M EH disulfoton (Di-Syston) H*** H H endosulfan (Iodan) M H EH ethyl parathion (Parathion) H*** H H fenamiphos (Nemacur) H*** H EH fonofos (Dyfonate) H H EH malathion L L EH methidathion (Supracide) H M EH methomyl (Lannate) H H H methyl parathion (Penncap-M) H*** H H oxamyl (Vydate) H H M
*Wildlife hazard is based on the following toxicities: H (Highly toxic) = LD50 less than 30 mg.kg and/or 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.
NT (Not toxic) **Fish 96-hour LC50 toxicities are as follows: EH (Extremely toxic) less than 0.1 ppm H (Highly toxic) 0.1-1.0 ppm M (Moderately toxic) 1-10 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. Hazard of Tobacco Insecticides to Wildlife
Wildlife Pest Problem Insecticide (Brand Name) hazard* Kills** Comments
Soil-Applied Insecticides
Aphids aldicarb (Temik 15G) high yes Temik granules exposed on the surface are a hazard to birds. (Flue-cured tobacco only.
Aphids (suppression acephate (Orthene 75SP) low no Di-Syston and Mocap Plus only) disulfoton (Di-Syston 15G) high yes granules on soil surface are disulfoton + ethoprop high yes a hazard to birds. (Mocap Plus 10 + 5G) fenamiphos (Nemacur 3E) high yes
Flea beetles oxamyl (Vydate L) low no Temik granules exposed on disulfoton (Dy-Syston 8) moderate yes the soil surface are a hazard ethoprop + disulfoton moderate yes to birds. (MoCap Plus EC) carbofuran (Furadan 4F) high yes aldicarb (Temik 15G) high yes (Flue-curred tobacco only)
Flea beetles and carbofuran (Furadan 4F) high yes Minimize drift into wildlife early-season habitat. hornworms
Wireworms chlorpyrifos (Losrban 4E) low no Fully incorporating granules chlorpyrifos (Lorsban 15G) moderate no reduces hazard. Disk under fonofos (Dyfonate 10G) moderate no granules spilled at row ends fonofos (Dyfonate 50W) low no or use liquid formulation. ethoprop (Mocap 10G, 6EC) high yes carbofuran (Furadan 4F) high yes (Flue-cured tobacco only) parathion (Parathion 4G, 10G) high yes (Flue-cured tobacco only)
Remedial Treatments for Insect Control In the Field
Aphids acephate (Orthene 75SP) low no Thiodan and Lannate are endosulfan (Thiodan 3EC) moderate no more toxic to birds and methomyl (Lannate 1.8L 90SP) moderate no mammals.
Budworms Bacillus thuringiensis safe no Orthene is safer than (Dipel, Javelin, Biobit) Supracide, Lannate, or acephate (Orthene 75SP) moderate no Thiodan. Liquid methyl methidathion (Supracide 2EC) moderate no parathion is more hazardous endosulfan (Thiodan 3EC) moderate no than Penncap-M. However, methomyl (Lannate 90SP, 1.8L) moderate no Penncap-M is a hazard methyl parathion (Penncap-M) moderate yes to bees.
Cutworms carbaryl (Sevin 5% bait) low no Dylox and Proxol are highly trichlorfon (Dylox, Proxol) low no toxic to fish and bees. acephate (Orthene 75SP) low no
Flea beetles carbaryl (Sevin 10D, 80S, 4F) low no See budworm comments for acephate (Orthene 75SP) low no Penncap-M. Supracide is less methidathion (Supracide 2EC) moderate no toxic than Lannate. methomyl (Lannate 90SP, 1.8L) moderate yes methyl parathion (Penncap-M) moderate yes
Grasshoppers malathion 5 lb/gal EC low no See budworm comments for acephate (Orthene 75SP) low no Penncap-M. carbaryl (Sevin 10D, 50W, 4F) low no methyl parathion (Penncap-M) moderate yes
Hornworms Bacillus thuringiensis safe no Lannate is hazardous when (Dipel, Javelin, Biobit) drift or spray reaches wildlife carbaryl (Sevin 80S, 10D, 4F) low no directly. See comments on acephate (Orthene 75SP) low no Penncap-M under budworm. methidathion (Supracide 2EC) moderate no methomyl (Lannate 90SP, 1.8L) moderate no methyl parathion (Penncap-M) moderate yes
Japanese beetles carbaryl (Sevin low no
Loopers Bacillus thuringiensis safe no See above for Lannate. (Dipel, Javelin, Biobit) acephate (Orthene 75SP) low no methomyl (Lannate 90SP, 1.8L) moderate no
Slugs metaldehyde + carbaryl bait high no Birds may be killed in hydrated lime low no methaldehyde-treated areas.
*Wildlife hazards:

high indicates possible wildlife deaths;
moderate indicates possible wildlife sickness, deaths less likely;
low indicates sickness unlikely.

**Kills:

yes indicates wildlife deaths due to use of the insecticide (active ingredient) have been reported.
no indicates wildlife deaths have not been reported when pesticide is used according to label.

Granular Insecticides

Granular formulations are a real hazard to birds. Birds eat granules exposed on the soil surface, mistaking the granules for food or grit. Ingesting only a few granules of a toxic insecticide can kill a small bird.

To reduce the danger to wildlife from granular insecticides:

Disking spilled granules into the soil at row ends is especially important since many birds feed on the edges of fields. When soil incorporation is not possible, consider using a liquid formulation following the guidelines in the next section.

The hazard to wildlife posed by some soil-applied systemic insecticides may warrant forgoing their use. Before using soil- applied systemic insecticides, consider their advantages and disadvantages discussed in the "Insect Management" section of the Tobacco Information handbooks (AG-376 and AG-178) published by the North Carolina Cooperative Extension Service.

Foliar Insecticides

The hazards of foliar-applied insecticides to wildlife range from low to high (see Table 1). Several insecticides are relatively safe; they include Bacillus thuringiensis (Biobit, Dipel, or Javelin), carbaryl (Sevin), malathion, and acephate (Orthene). Other foliar insecticides, such as methomyl (Lannate), methidathion (Supracide), and methyl parathion are highly toxic to wildlife. Most foliar insecticides used on tobacco are short-lived in the environment, so the hazard to wildlife is short-term.

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 appropriate pressure and volume for the chosen nozzle, and adding a drift control agent. Ultra-low-volume sprays are more likely to cause drift than low-pressure sprays. Of course, avoid spraying when the wind is blowing faster than 8 mph.

Nematicides

Several soil-incorporated granular insecticides are also used as nematicide treatments and are highly toxic to wildlife; these include fenamiphos (Nemacur), aldicarb (Temik), ethoprop (Mocap), and carbofuran (Furadan). If these pesticides are used, it is very important to incorporate the granules into the soil to reduce wildlife hazard. Also, liquid formulations, rather than granular, may reduce wildlife hazard. Chlorpyrifos (Lorsban) and oxamyl (Vydate) are the least hazardous nematicide alternatives but are not as effective as some others in controlling nematodes.

Some fumigants are less hazardous to wildlife than nonfumigants because of their short duration of activity. These fumigants include dichloropropene (Telone II) and methyl bromide with chloropicrin (Brom-O-Sol).

Proper cultural practices, including crop rotation, stalk and root destruction, and use of resistant tobacco varieties, help to reduce the use of nematicides. For more information, see Extension Service publication AG-187, Tobacco Information.

Fungicides

Fungicides used on tobacco are only slightly toxic to wildlife; these include metalaxyl (Ridomil), ferbam (Carbamate), and mancozeb (Dithane M-45). Their use does not present a hazard to wildlife. However, mancozeb is highly toxic to fish.

Fungicide use can be reduced by controlling seedling diseases with cultural practices such as proper rotation, timely planting, and proper seed selection.

Herbicides

Most herbicides used on tobacco are only slightly toxic to wildlife (although some are highly toxic to fish). However, herbicides can destroy wildlife habitats and reduce the food and cover available to wildlife. When habitats are reduced on a farm, there is a tremendous effect on the wildlife populations there. Wildlife populations decline when herbicides or mechanical methods are used to maintain "clean" fencerows, ditch banks, and field borders. These strip habitats provide wildlife valuable cover for nesting, brood rearing, and escaping from predators.

Many species of wildlife, including quail and rabbits, benefit from strip habitats. Where possible, consider maintaining these areas in wildlife cover. Protect these areas from herbicides and mow less frequently. Consider mowing filter strips and ditch banks only once per year, preferably in early spring. In fields where weeds have been a problem, prevention of weed seed production in non-crop habitats may be accomplished by using selective herbicides that allow grass cover to be maintained.

Ways to Reduce Pesticide Use

Reducing pesticide use is one of the best ways to protect fish and wildlife resources. Using sound cultural practices reduces pest problems and, therefore, results in lower pesticide use. Cultural practices that decrease the need for pesticides include rotating crops, selecting resistant varieties (when possible), planting and harvesting at the proper time, and using integrated pest management (IPM) techniques. 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 and the environment. For further information on alternatives to pesticide use, see the list of additional readings at the end of this publication.

Remember These Tips To Protect Fish and Wildlife Resources

For Further Information

Other publications that discuss pesticides and the protection of wildlife are listed below. For further information on this topic, contact your county Extension Service agent.

Additional publications in the Pesticides and Wildlife series include: