Pesticides & Wildlife - Cotton

Authors: William E. Palmer and Peter T. Bromley

North Carolina Cooperative Extension Service AG-463-4

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 fishemenr alone.

Cotton fields provide both food and cover for wildlife. For example, quail and other birds nest in grassy strips alongside cotton 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 these 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 become sick or die. In a 1978 study of quail living near cotton fields that had been sprayed with methyl parathion, 35 percent had enough insecticide in their bodies to cause sickness or death. Birds that are made sick by insecticides may neglect their young, abandon their nests, and become more susceptible to predators or 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 destroying 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 cotton fields can harm wildlife and (2) describes how farmers can minimize adverse effects of pesticides on wildlife.

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 more information on alternatives to pesticide use, contact your county Extension Service agent.

Insecticides

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

Tables 1 and 2 list insecticides recommended ommended in the North Carolina Agricultural Chemicals Manual for use on cotton. 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 unikely. Insecticides rated low are unlikely to harm Wildlife directly.

At-Planting Soil Insecticides

Several granular at-planting soil insecticides used in cotton production are toxic to wildlife and have caused wildlife die-offs; these include aldicarb (Temik), phorate (Thimet), and disulfoton (Di-Syston), Granular insecticides are a serious hazard to birds. Birds eat granules exposed on the soil surface, mistaking them for food and grit. Ingesting just a few granules of a toxic insecticide can kill a small bird.

To reduce the hazardous effects of granular insecticides on wildlife:

Spilled granules at row ends are particularly hazardous since birds often search field edges for food and grit. Full incorporation, including disking under spilled granules at row ends, reduces wildlife poisonings caused by granular soil insecticides.

Liquid Insecticides

Several foliar insecticides used on cotton are extremely toxic to wildlife; these include phosphamidon (Dimecron), dicrotophos (Bidrin), and dimethoate (Cygon). When foliar sprays are necessary, the risk to wildlife can be minimized by choosing the least toxic alternative.

VVhen multiple sprays are necessary to control a pest, the hazard to wildlife is increased. Birds that survive a single exposure to an insecticide are more likely to die if they are exposed again. Recovery from exposure to an organophosphate insecticide, such as dicrotophos (Bidrin), can take 30 days. Therefore, it is even more important to use the least toxic material to wildlife when several sprays are needed.

To reduce hazard to wildlife from liquid formulations:

Several studies of aerial applications of pesticides have reported significant drift of material into nearby wildlife habitats. If it is necessary to use highly toxic insecticides, apply them with ground equipment; this will help to minimize drift and reduce the hazard to wildlife. Ground application may also allow wildlife more time to leave the area during the spraying operation.

Spray 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.

Disease Control

Fungicides

Most fungicides are only slightly toxic and do not present a hazard to birds and mammals; they include PCNB (Terraclor), ETMT (Super-X), Metalaxyl (Ridoniil PC), and captan. Some fungicides are highly toxic to fish; these include captan and PCNB.

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

Nematicides

Nematicides used on cotton include dichloropropene (Telone II), fenamiphos (Nemacur), and aldicarb (Temik). Nemacur and Temik are more hazardous to wildlife than Telone II because they stay active in the environ- ment longer and have been reported to cause wildlife mortality. Although Telone II is toxic to wildlife, its use has not been reported to cause wildlife poisonings. This is probably because it does not stay active for long and its application procedures are different.

The hazard to wildlife from nematicides can be reduced by rotating crops, applying chemicals only when economic thresholds are reached, and using the least toxic alternative. Danger to wildlife from granular nematicides is reduced when granules are fully incorporated into the soil. Disking spilled granules into the soil significantly reduces danger to wildlife.


	Table 1. Toxicity of Pesticides Used on Cotton
        to Birds, Mammals, and Fish
_________________________________________________________
	Pesticide (Brand Name)	   Birds   Mammals   Fish
_________________________________________________________

	acephate (Orthene)	     M	     L        L
	aldicarb (Temik)	     Hc	     H        H
	bifenthrin (Capture)	     L	     L        EH
	cyfluthrin (Baythroid)	     L       L	      EH
	chlorpyrifos (Lorsban)	     H	     L        EH

	cypermethrin (Cymbush)	     L       M 	      EH
	dicofol (Kethane)	     H       L	      H
	dicrotophos (Dimecron)	     Hc      H        M
	dimethoate (Cygon)	     Hc	     M        M
	disulfoton (Di-Syston)	     Hc	     H        H

	esfenvalerate (Asana XL)     L	     L 	      EH
	fenamiphos (Nemacur)	     Hc	     H        EH
	lambda cyhalophrin (Karate)  L       L	      EH
	methidathion (Supracide)     H       M        EH
	methomyl (Lannate)	     H	     H        H

	methyl parathion (Penncap-M) Hc      H        M
	oxydementon-methyl	     H       M        M
	(Metasystox-R),
	permethrin (Ambush, Pounce)  L       L	      EH
	phorate (Thimet)	     Hc	     H        EH
	phosphamidon (Dimecron)	     Hc      H        M	

	propargite (Comite)	     L       L        H
	profenofos (Curacron)	     -       L        EH
	sulprofos (Boistar)	     H       L        H
	thiodicarb (Larvin)          M       H	      H
	tralomethhn (Scout X-tra)    L       L        EH
_________________________________________________________
Wildlife hazard is based on the following toxicities:
   H(Highly toxic) = LD50 < 30 mg/kg and/or LC50 < 500 ppm.
   M(Moderately toxic) = LD50 > 30 and < 100 mg/kg and/or
        LC50 > 500 and < 1000 ppm.
   L(Low toxicity) = LD50 > 100 mg/kg and LC50 > 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 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.

c = Active ingredient (not necessarily a specific product)
   has caused wildlife deaths.
 



Table 2. Hazards of Insecticide Sprays Used on Cotton to Wildiife
________________________________________________________________________________________________
			                     Wildlife  Wildlife
Insect	          Insecticide (Brand Name)     hazard	kills	Comments
________________________________________________________________________________________________
Aphids	         bifenthrin (Capture)	       low	no	Aphid control with insecticides
	         dimethoate (Cygon)           high	yes	should be attempted only as a
	         phosphorothioate 	      moderate	no	resort, especially early in
	          (Metasystox-R)                                the season. Dimecron and Bidrin
	         methyl parathion(Penncap-M)  moderate	yes	may be cancelled.
	         phosphamidon (Dimecron,Swat)  high	yes
     	         dicrotophos (Bidrin)	       high	yes
________________________________________________________________________________________________
Beet and fall	 chlorpyrifos (Lorsban)	      moderate	no	See comment on
armyworms	 sulprofos (Bolstar)	      moderate	no	Lannate under bollworm.
		 profenofos. (Curacon)	       low	no
		 thiodicarb (Larvin)	      moderate	no
		 methomyl (Lannate)	      moderate	no
________________________________________________________________________________________________
Bollworm	bifenthrin (Capture)	       low	no	Lannate is very toxic to birds
		cyfluthrin (Baythroid)	       low      no	and mammals. Residues
		cypermethrin (Ammo)	       low	no	disappear quickly. Hazard is
		esfenvalerate (Asana XL)       low	no	greatest when wildlife enter
		lambda cyhalothrin (Karate)    low	no	fields soon after spraying or are
		tralomethrin (Scout X-tra)     low	no	sprayed directly. See Table 1
		suprofos (Bolstar)	     moderate	no	for information on toxicity to
		profenotos (Curacon)	       low	no      fish.
		thiodicarb (Larvin)	     moderate	no
		methomyl (Lannate)	     moderate	no
________________________________________________________________________________________________
Cabbage and	acephate (Orthene)	       low	no	Treatment is generally not
soybean loopers				                        recommended.
________________________________________________________________________________________________
European corn 	bifenthrin (Capture)	       low	no
borer           lambda cyhalothrin (Karate)    low	no
		cyfluthrin (Baythroid)	       low	no
________________________________________________________________________________________________
Spider mites	methidathion (Supracide)     moderate	no
		propargite (Comite)	       low	no
		dicofol (Kelthane)	     moderate	no
________________________________________________________________________________________________
Stink bugs	methyl parathion	     moderate	yes	Known mortality occurred with
		(Penncap-M)			                liquid, not encapsulated,
					                        formulation.
________________________________________________________________________________________________
Thrips	        acephate (Orthene)	        low	no	Bidrin and Dimecron are
		dimethoate (Cygon)	        high	yes	extremely toxic to wildlife.
		dicrotophos (Bidrin)	        high	yes
		phosphamidon (Dimecron, Swat)	high	yes
_______________________________________________________________________________________________
Wildlife hazards:
   high indiicates possible wildlife deaths;
   moderate indicates possible woldlife 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.

Herbicides

Most herbicides used on cotton are only slightly toxic to birds and mammals. One exception is paraquat (Gramoxone). Paraquat is toxic to birds and bird embryos. Some herbicides are highly toxic to fish; these include fluazifop (Fulsilade 2000), fluometuron (Cotoran), oxyfluorfen (Goal), pendimethalin (Prowl), and trifluralin (Treflan).

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 herbcidesi 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 during early spring. If possible, mow on a two-year rotation. For example, mow one side of a ditchbank in the first year and the other side in the second year. This method provides year-round habitats for wildlife. Disking filter strips and field borders, rather than mowing, encourages growth of important wildlife food plants and improves the structure of the habitat for wildlife.

Remember These Tips to Protect Fish and Wildlife Resources

For Further Information

For further information on this topic, contact your county Extension Service agent.

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