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.
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.
To reduce the hazardous effects of granular insecticides on wildlife:
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:
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.
Fungicide use can be reduced by controlling seedling diseases with cultural practices such as proper rotation, timely planting, and proper seed selection.
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.
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.