Pesticides and Wildlife - Soybeans

Authors:William E. Palmer, Peter T. Bromley, and John R. Anderson, Jr.

North Carolina Cooperative Extension Service AG-463-1

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 fisher- men alone.

Soybean fields provide a good habitat for wildlife. For instance, deer and rabbit eat the forage and use these fields for cover. Quail and their young feed on the insects and weed seeds. During winter, leftover, unharvested grain provides wildlife with a valuable source of food.

Pesticides used on soybean fields can harm wildlife living in or around these fields. For example, direct exposure to toxic pesticides may cause wildlife to become sick or die. A study in North Carolina in 1978 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.

Pesticides can also affect wildlife indirectly; herbicides or insecti- cides can reduce the food and cover that wildlife need in order to survive. Populations of gamebirds decrease when herbicides and insecticides are used intensively. . 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 soybean 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 practces 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 agri-chemicals. For instance, planting soybeans in narrow rows rather than wide rows helps to reduce corn earworm problems in late summer. 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

Many organophosphate and carbamate insecticides that are used on soybeans are highly toxic to wildlife; these include aldicarb (Temik), ethoprop (Mocap), chlorpyrofos (Lorsban), and methomyl (Lannate). Wildlife are exposed to insecticides when they eat granules or chemical residues on plants or in insects. Wildlife that enter fields soon after spraying may also be exposed when they inhale insecticide vapor or when insecticides contact their skin or eyes. Exposure can be substantial. For example, researchers in Virginia tested quail that had been killed by hunters and found that 60 percent of the quail had insecticides in their bodies.

Exposure to organophosphate and carbamate insecticides can disrupt an animal's nervous system. If exposure is great enough, sickness and death occur. The nervous system may not return to normal for 4 weeks following exposure to these insecticides. The effects are additive if an animal is exposed more than once. This means that wildlife are more likely to become sick or die from multiple expo- sures.

Tables 1 and 2 list insecticides recommended in the North Carolina Agricultural Chemicals Manual for use on soybeans. Table 1 rates insecticides accord- ing 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, moder- ate, 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. Insecti- cides rated moderate may also cause death or sickness, although death is unlikely. Insecticides rated low are unlikely to harm wildlife directly.

Granular Insecticides

Granular formulations of insecti- cides are a serious hazard to birds. Some very toxic agri- chemicals, such as aldicarb (Temik) and ethoprop (Mocap), are commonly formulated as granules. Birds eat granules exposed on the soil surface, mistaking them for food or grit. Ingestion of a few granules of a highly toxic insecticide can kill a small bird.

To reduce the danger to wildlife from granular formulations:

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

Incorporation of granules is required on pesticide labels. Disking under granules spilled at row ends is particularly important because birds look for food and grit near the edges of soybean fields and may eat the granules left uncovered at the ends of rows. If soil incorporation is not possible, consider using a recom- mended liquid formulation following the guidelines in the next section.

Liquid Insecticides

Liquid formulations of insecticides used on soybeans are generally less toxic to wildlife than granular formulations. Insecticides such as permethrin (Pounce or Ambush) and esfenvalerate (Asana XL) are only slightly toxic to birds and mam- mals, although extremely toxic to fish.

In contrast, some insecticides are highly toxic to birds and mammals and their use constitutes a hazard to wildlife; these include methomyl (Lannate), methyl parathion, and chlorpyrifos (Lorsban). The threat to wildlife is greatest during and immediately after spray applications. For example, quail entering a recently sprayed soybean field to feed on insects may be killed or made sick by the insecticide.

To reduce danger to wildlife from liquid insecticides:

spray only when IPM thresholds are reached
use the least toxic insecticide that will control the insect pest
minimize drift of insecti cides into wildlife habitats.

Several studies of aerial applica- tions 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 opera- tion.

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 setup, 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 and Fungicides

Nematicides that are often used in soybean fields include fumigants, granules, and liquid formulations. Some nematicides are highly toxic to wildlife and have caused wildlife deaths; these include ethoprop (Mocap) and aldicarb (Temik). Fumigant formulations (such as Telone II) are probably safer for wildlife, based on their short duration of activity and the methods used to apply them. Nematicide granules exposed on the soil surface pose the greatest hazard to wildlife. Therefore, fully incorporate granules immediately after application. Disking under spilled granules at row ends will significantly reduce hazard to wildlife.

Fungicides currently recom- mended for use on soybeans, include metalaxyl (Ridomil, Subdue, Apron), carboxin (Vitavax), and Thiram. These fungicides have a low toxicity to birds and mammals, so they do not present a hazard to wildlife. Thiram, however, is highly toxic to fish.

Table 1. Toxicity ot Common Insecticides and Nematicides
          Used on Soybeans to Birds, Mammals, and Fish
________________________________________________________

Insecticide (Brand Name)      Birds  Mammals  Fish

acephate (Orthene)	        M	L	L
aldicarb (Temik)	        Hc	H	EH
Bacillus thuringieinsis	        NT	NT	L
carbaryl (Sevin)	        L	L	M
chlorpyrffos (Lorsban)	        H	L	EH
esfenvalerate (Asana XL)	L	L	EH
ethoprop (Mocap)	        Hc	M	H
methomyl (Lannate)	        H	H	H
methyl parathon		        Hc	H       H
permethrin (Ambush, Pounce)	L	L	EH
thiodicarb (Larvin)	        H	H	M
tralomethrin (Scout)	        L	L	EH
________________________________________________________
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
                         1000 ppm.
   L(Low toxicity) = LD50 greater than 100 mg/kg and
                     LC50 greater than 1000 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 Soybeans to Wildlife
___________________________________________________________________________________________________
			                       Wildlife Wildlife
Insect	            Insecticide (Brand Name)	hazard	  kills	 Comments
____________________________________________________________________________________________________
Bean leaf 	carbaryl (Sevin)	        low	   no	 Lorsban is toxic to birds and fish.
    beetle      chlorpyrifos (Lorsban)	        moderate   no
____________________________________________________________________________________________________
Beet armyworm	thiodicarb (Larvin)     	moderate   no	
		methomyl (Lannate)	        moderate   no	
		chlorpyrifos (Lorsban)	        moderate   no
____________________________________________________________________________________________________
Corn earworm	esfenvalerate (Asana XL)	low	   no	Asana,Ambush, Pounce, Scout,
		permethrin (Ambush, Pounce)	low	   no	and Lorsban are extremely toxic
		tratomethrin (Scout)	        low	   no	to fish. Lannato is-very toxic to
		carbaryl (Sevin)	        low	   no	birds and mammals.
		methomyl (Lannate)	        moderate   no
		chlorpyrifos (Lorsban)  	moderate   no
		thiodicarb (Larvin)        	moderate   no
____________________________________________________________________________________________________
Grasshopper	acephate (Orthene)	        low	   no	Lorsban is more hazardous than
		chlorpyrifos (Lorsban)	        moderate   no	Orthene.
____________________________________________________________________________________________________
Green           Bacillus thuringiensis  	low	   no	Lannate is the most
   cloverworm	(Bactur, Dipel, others)			        acutely toxic alternative.
		carbaryl (Sevin)	        low	   no	Lannate is toxic to birds
		thiodicarb (Larvin)	        moderate   no	and mammals.
		methontyl (Lannate)	        moderate   no
____________________________________________________________________________________________________
Soybean looper	Bacilluu thuringiensis  	low        no	See comments for corn earworm.
		(Dipel, Javelin, others)
		permethrin (Ambush, Pounce)	low	   no
		methomyl (Lannate)	        moderate   no
		thiodicarb (Larvin)	        moderate   no	
____________________________________________________________________________________________________
Stink bugs	tralomethrin (Scout)    	low	   no	Methyl-parathion encapsulated
		acephate (Orthene)	        low	   no	formulation may be safer than
		methyl parathion (Penncap-M,	high	   yes	EC formulations.
		methyl parathion EC)
____________________________________________________________________________________________________
Velvethean 	Bacfllus thurinigiensis	        low	   no	See comments for corn earworm.
  caterpillar	(Dipel, Javelin, others)
		esfenvalerate (Asana XL)	low	   no
		permethrin (Ambush, Pounce)	low	   no
		tralomethrin (Scout)	        low	   no
		carbaryl (Sevin)	        low	   no
		methomyl (Lannate)	        moderate   no
		chlorpyrifos (Lorsban)	        moderate   no
		thiodicarb (Larvin)	        moderate   no
___________________________________________________________________________________________________
Wildlife hazards:
  high indicates possible wildlife deaths;
  moderate indicates possible wildlife sickness, death less likely;
  low indicates sickness unlikely.

Kills:
  yes indicates wildlife deaths due to use of this 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 soybeans are only slightly toxic to birds and mammals. One exception is paraquat (Gramoxone Extra or Gramoxone Plus), which is moderately toxic to birds and causes abnormal growth of bird embryos when sprayed directly on the eggs. Waterfowl eggs are particularly sensitive to paraquat. Generally, herbicides do not directly affect wildlife. More often, herbicides affect wildlife by damaging their habitats.

When habitats are reduced on a farm, there is a tremendous effect on the wildlife populations there. Wildlife need food and cover to survive. 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 or less frequently, if possible. Mow during early spring only. Consider mowing only one side of a ditch bank or fencerow each year to provide year round cover.

Remember These Tips to Protect Fish and Wildlife Resources

Incorporate IPM practices into your soybean 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 low-pressure 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.

For Further Information

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

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