CORN

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.

Corn fields provide both food and cover for wildlife. During the summer, deer and other wildlife find cover in corn fields. Untilled fields provide nesting areas for bobwhite quail and other birds. During winter, corn fields that have not been tilled after harvest provide about 300 pounds of spilled grain per acre as a food source. When wildlife such as deer, turkey, and quail have access to this unused grain, they are more likely to survive the winter and successfully reproduce the following spring.

Pesticides used in corn production may harm wildlife living in or around corn fields. They can affect wildlife in two ways. First, when an animal is directly exposed to a highly toxic pesticide, it can become sick or die. A study in North Carolina indicated that more than 30 percent of the quail tested were made sick by one aerial insecticide application. Once sick, wild birds may neglect their young, abandon their nests, and become more susceptible to predators or disease.

Second, pesticides affect wildlife indirectly by reducing food supplies and vegetative cover. Populations of gamebirds are reduced when herbicides and insecticides are intensively used. These pesticides can destroy brood cover and reduce insect and plant foods, lowering the survival rate of gamebird chicks.

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

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.

Insecticides

Species that live in and around corn fields are exposed to insecticides when they eat granules and chemical residues on plants or in insects. Wildlife that enter crop fields soon after an insecticide has been sprayed are exposed when they inhale its vapor or when the insecticide contacts their skin or eyes.

Tables 1 and 2 list insecticides recommended in the North Carolina Agricultural Chemicals Manual for use on corn. 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.

Granular Insecticides

Granular insecticides present a serious hazard to birds. Many highly toxic insecticides are formulated as granules, such as fonofos (Dyfonate) and terbufos (Counter). Birds eat granules exposed on the soil surface, mistaking them for food and grit. Ingesting only a few granules of a toxic insecticide can kill a small bird.

To reduce the hazard to wildlife from granular formulations:

• use the least toxic insecticide that will control the insect pest
• fully incorporate granules into the soil.

Incorporation is especially important near field edges where many birds search for food and grit. Disking spilled granules under the soil at row ends significantly reduces wildlife exposure to the granules. If soil incorporation is not possible, consider using a liquid formulation following the guidelines in the next section.

Liquid Insecticides

Several insecticides that are sprayed on corn foliage are toxic to wildlife; these include carbofuran (Furadan), methyl parathion, and methomyl (Lannate). Other foliar insecticides are only slightly toxic to most birds and mammals; for example, malathion, carbaryl (Sevin), esfenvalerate (Asana XL), and permethrin (Pounce or Ambush). However, many of these insecticides are toxic to fish and other aquatic animals (see Table 1).

To reduce danger to wildlife from foliar applications:

• spray only when IPM thresholds are met
• use the least toxic insecticide that will control the insect pest
• minimize drift of insecticides into wildlife habitats.

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. Ultra­low­volume 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

Nematicides commonly used on corn include carbofuran (Furadan), ethoprop (Mocap), and terbufos (Counter). All three are highly toxic and therefore potentially hazardous to wildlife. If granular formulations are used, full incorporation is required on the label. Incorporating spilled granules at row ends greatly reduces the danger to wildlife that feed along the edges of treated fields.

Herbicides

Most herbicides used during corn production are only slightly toxic to birds and mammals. One exception is paraquat (Gramoxone), which is moderately toxic to birds. When paraquat is sprayed directly on bird eggs it can cause abnormal growth of embryos and has been shown to reduce the hatching success of waterfowl eggs. Some herbicides are very toxic to fish, such as pendimethalin (Prowl) and bromoxynil (Buctril). Care should be taken to ensure ponds and streams are not contaminated with herbicides.

Herbicides can harm or destroy wildlife habitats. Herbicide use can often be reduced by employing IPM practices. Keep records of weed problems and use postemergent herbicides only when needed. New postemergent herbicides (such as Accent or Dimension) may help to reduce costs and the total amount of herbicide needed. When applying herbicides, avoid spraying past the outer row of corn because it wastes chemical and can destroy wildlife habitats.

Also, protecting noncrop areas from herbicides is important. Wildlife, especially small game and song birds, benefit from the cover provided by strip habitats. These strips are linear noncrop areas, such as hedgerows, ditch banks, filter strips, field borders, and fencerows. The vegetation in strip habitats provides wildlife valuable cover for nesting, brood rearing, and escaping from predators. These habitats also allow wildlife safe access to corn fields during winter months when these fields provide a good source of food.

Mowing strip habitats also reduces their value for wildlife. When field borders, filter strips, ditch banks, and other fallow areas are mowed during spring and summer, wildlife cover is reduced. Consider maintaining strip habitats by mowing only once per year or less frequently if possible. Mow during early spring only. Mowing alternate sides of strip habitats every other year will ensure that cover will be available to wildlife year­round.

Table 1. Toxicity of Pesticides Used on Corn to Birds,

Mammals, and Fish

Pesticide(Brand Name)	Birdsa	Mammalsa	Fishb
carbaryl (Sevin)	L	L	H
carbofuran (Furadan)	HC	H	H
chlorpyrifos (Lorsban)	H	L	EH
esfenvalerate (Asana XL)	L	L	EH
ethoprop (Mocap)	HC	M	H
fonofos(Dyfonate)	H	H	EH
malathion	L	L	EH
methomy''(Lannate)	H	H	H
methyl parathion	Hc	H	H
permethrin(Ambush, Pounce)	L	L	EH
terbufos (Counter)	H	H	EH

^a Wildlife hazard is based or, the following toxicities:

• H (Highly toxic) = LD50 less than 30 mg/kg and/or LC50 less than 500ppm.
• 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)

^b Fish 96 hour LC50 toxicities are as follows:

• H (Extremely toxic) less than 0.1ppm
• H (Highly toxic) 0.1 to 1.0 ppm
• M (Moderately toxic) 1 to 10 pprn
• L (Low toxicity) greater than 10 ppm.

To convert fish toxicities to pounds of active ingredient per acre foot of water. Multiply bv 2.7.

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

Table 2. Hazards of Insecticides Used on Corn to Wildlife

Insect	Insecticide(Brand Name)	Wildlife hazarda	Killsb	Comments
Billbugs (at planting)	chlorpyrifos 15G (Lorsban) carbofuran 4F (Furadan)	moderate high	no yes	Disk under Lorsban at row ends.
Billbugs (postemergence)	chlorpyrifos 4EC (Lorsban) terbufos 1 5G (Counter) carbofuran 4F (Furadan)	moderate moderate high	no no yes	Fully incorporate Counter granules. Exposed granules are a hazard to birds
Corn earworm (in whorl)	methomyl (Lannate) chlorpyrifos 4EC (Lorsban)	moderate moderate	no no
Gorn leaf aphid	malathion 57EC methyl parathion4EC	low high	no yes	Methyl parathion is highly toxic to birds.
Cutworms (postemergence)	esfenvalerate (Asana XL) permethrin (Pounce, Ambush) chlorpyrifos EC (Lorsban) methyl parathion (Penncap­M)	low low moderate moderate	no no no yes	Directed ground application reduces wildlife hazard Liquid formulation of methyl parathion increases hazard.
Cutworms (preemergence)	chlorpyrifos 1 5G (Lorsban) fonofos 10G,20G (Dyfonate)	low		Fully incorporate granules or use liquid formulations.
European corn borer (first generation)	esfenvalerate (Asana XL) permethrin (Ambush, Pounce) chlorpyrifos 1 5G (Lorsban) methyl parathion (Penncap­M) carbofuran 4F (Furadan)	low low high moderate high	no no no yes yes	Broadcasting Lorsban increases hazard to birds. Furadan is extremely hazardous to birds.
European corn borer (second generation)	permethrin (Pounce) chlorpyrifos 1 5G (Lorsban)	low high	no yes	Broadcasting Lorsban increases hazard to birds.
Grasshoppers	chlorpyrifos EC (Lorsban)	moderate	no	Chlorpyrifos is toxic to fish.
Sod webworm Chinch bug	carbaryl (Sevin)	low	no	Safe. Apply to the base of plants.
True armyworm Corn earworm (in whorl and on foliage)	esfenvalerate (Asana XL) permethrin (Ambush, Pounce) carbaryl (Sevin) methomyl (Lannate) chlorpyrifos 4EC (Lorsban)	low low low moderate moderate	no no no no no	Esfenvalerate, permethrin, and chlorpyrifos are extremely toxic to fish.
Wireworms Corn rootworms	chlorpyrifos 1 5G (Lorsban) terbufos 1 5G (Counter) carbofuran 4F (Furadan) fonofos 10G, 20G (Dyfonate)	moderate moderate high high	no no yes no	Fully incorporate granules, including spills at row ends, to reduce hazard to wildlife.

^a Wildlife hazards

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

^b 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.

Remember These Tips to Protect Fish and Wildlife Resources

• Incorporate IPM practices into your corn production.
• Use proper cultural practices that help to reduce pesticide use.
• Use the pesticide least toxic to fish and wildlife to get the job done.
• Protect field borders and other noncrop habitats from herbicides and insecticides.
• Never spray leftover pesticides into wildlife habitats.
• Fully incorporate pesticide granules, especially spilled granules at the ends of rows.
• Minimize drift when applying chemicals around fish and wildlife habitats by using low­pressure sprays and selecting nozzles that produce large droplets.
• Protect fish ponds and wetlands by avoiding spraying over ponds or drainage ditches.
• Never wash equipment or containers where rinse water could enter ponds or streams.
• Read and follow the instructions on the Pesticide label.

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