Pesticides & Wildlife-Small Grains

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

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. Hunters and fishermen in North Carolina spend more than $1 billion pursuing their sport each year.

Small grains provide food and cover to many wildlife species. Birds such as mourning doves feed on small grain seeds planted in the fall. Quail and songbirds feed on insects and other food items in small grain fields during spring. Wildlife also find food and cover in areas adjacent to crop fields, such as hedgerows, unmowed ditch banks, and field borders.

Pesticides used on small grains can harm wildlife. For example, exposure to a highly toxic insecticide can cause sickness or death. Once sick, wildlife may neglect their young, abandon their nests, and become more susceptible to predation and disease. Pesticides can harm wildlife indirectly as well. When herbicides or insecticides are sprayed on field borders and other noncrop habitats, wildlife lose valuable escape cover and food. Studies on game birds have shown that maintaining noncrop areas in wildlife habitat can increase populations.

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

Insecticides

Exposure to organophosphate and carbamate insecticides disrupts an animal's nervous system. Exposure to highly toxic insecticides can lead to sickness and death. The nervous system of the sickened animal may not return to normal for several weeks following exposure. Animals made sick by an insecticide are more likely to die if they are exposed again.

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

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

Pesticide (Brand Name)      Birds*          Mammals*           Fish**

azinphos-methyl (Guthion)     H***             H                EH
carbaryl (Sevin)              L                L                M
carbofuran (Furadan)          H***             H                H

chlorpyrifos (Lorsban         H                L                EH
dimethoate (Cygon)            H***             M                M
Disulfoton (Di-Syston)        H***             H                H

malathion                     L                L                EH
methomyl (Lannate)            H                H                H
methyl parathion              H***             H                H

*Wildlife hazard is based on the following toxicities: 
 H (Highly toxic)  = LD50 less than 30 mg/kg and LC50 less than 500
ppm. 
 M (Moderately toxic)  = LD50 greater than 30 and less than 100 mg/kg
and/or LC50 greater than 5 500 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 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.

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


Table 2.  Hazard of Insecticides Used on Small Grains and Sorghum to
Wildlife

                                       Wildlife
Insect     Insecticide (Brand Name)     hazard*   Kills**  Comments

 Insect Control in Small Grains  

Aphids     disulfoton (Di-Syston)      high       yes      Methyl parathion is
                                                           toxic to bees.
           dimethoate (Cygon)          high       yes      Malathion is the    
           encapsulated methyl                             safest material for
             parathion (Penncap-M)     moderate   no       wildlife. Disulfoton
           methyl parathion            high       yes      is less hazardous when
           malathion                   low        no       applied directly to
                                                           soil.


Cereal     azinphos-methyl (Guthion)   high       yes      Methyl parathion is
           carbaryl (Sevin)            low        no       toxic to bees.    
           encapsulated methyl                             Azinphos-methyl and
            parathion (Penncap-M)      moderate   no       methomyl are toxic to
           malathion                   low        no       wildlife. Sevin and 
           methomyl (Lannate)          moderate   no       malathion are safer 
                                                           for wildlife.


Fall       methomyl (Lannate)          moderate   no       Treat only when IPM
armyworm                                                   thresholds are
                                                           exceeded.


True       carbaryl (Sevin)            low        no       Carbaryl and trichlor-
armyworm   encapsulated methyl                             fon are safest for  
             parathion (Penncap-M)     moderate   no       wildlife. Best results 
           methomyl (Lannate)          moderate   no       occur when tempera- 
           methyl parathion            high       yes      tures are warm and 
           trichlorfon (Dylox,                             caterpillars are    
             Proxol)                   low        no       active.

 Insect Control in Sorghum  

Aphids     dimethoate (Cygon)          high       yes      Malathion is safer  
           malathion                   low        no       than dimethoate.

Cinch bug  carbaryl (Sevin)            low        no

Corn       carbaryl (Sevin)            low        no       Although methomyl is
earworm    chlorpyrifos (Lorsban)      moderate   no       the material of  
Fall       methomyl (Lannate)          moderate   no       choice, it is highly
armyworms                                                  toxic and care should
Webworms                                                   be taken to avoid
armyworms                                                  drift of material
                                                           into wildlife
                                                           habitats.

Sorghum    carbaryl (Sevin)            low        no       Carbaryl has low
midge                                                      toxicity to most birds
                                                           and mammals.


*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

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.

Liquid Insecticides

Carbaryl (Sevin) and malathion present a low hazard to wildlife. Trichlorfon (Dylox, Proxol) is also relatively safe.

To reduce danger to wildlife from liquid insecticides:

• spray only when IPM thresholds are met

• use the least toxic insecticide that will control the insect pest (see Table 1)

• minimize drift of insecticides into wildlife habitats and ponds or streams.

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 the addition of a drift control agent. Ultra-low-volume sprays are more likely to cause drift then low-pressure sprays. Finally, never spray when the wind is blowing faster than 8 mph.

Fungicides

Fungicide use can be reduced by controlling diseases with cultural practices such as longer rotations, timely planting, and careful seed selection (see Extension Service publication AG-419-7, Small Grain Production Guide No. 7, Disease Management.

Herbicides

Wildlife need food and cover to survive. When wildlife habitats on a farm are lacking or of poor value, wildlife populations decline. Noncrop areas adjacent to crop fields, such as ditch banks, field borders, and filter strips, can provide habitat for wildlife if managed correctly. These strip habitats can provide nesting areas, protection from predators, and travel corridors for wildlife.

Several management techniques can be used to improve strip habitats for wildlife. Protect field borders and other habitats from herbicides. Mow strip habitats only once per year, preferably during early spring. If possible, mow on a two- year rotation. For example, mow one side of a ditch bank and filter strip in the first year and the other side in the second year. Disking field borders and filter strips, rather than mowing, stimulates growth of favorable wildlife food plants. Where wildlife are a priority, create filter strips and field borders no less than 12 feet in width. Cost-sharing programs are available to develop filter strips. Filter strips also protect water quality by reducing runoff of pesticides and soil.

Ways to Reduce Pesticide Use

Remember These Tips To Protect Fish and Wildlife Resources

• Incorporate IPM practices into your small grain 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 not 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

Additional publications in the Pesticides and Wildlife series include:

• Soybeans, AG-463-1
• Corn, AG-463-2
• Tobacco, AG-463-3
• Cotton, AG-463-4
• Peanuts, AG-463-5
• Fruit Trees, AG-463-7
• Christmas Trees, AG-463-8

Small Grain Production Guide No. 7, Disease Identification, AG-419-7