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. 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.
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, maintaining proper fertility, 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" level 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 small grains are highly toxic to wildlife;
these include carbofuran (Furadan), dimethoate (Cygon), disulfoton (DiSyston),
methomyl (Lannate), and methyl parathion. Wildlife are exposed to insecticides
when they eat chemical residues on plants or in insects. Wildlife that are in
fields or enter fields soon after an insecticide has been sprayed are exposed
when they inhale vapor or when insecticides contact their skin or eyes. Such
exposure can be substantial. In Virginia, researchers found that 60 percent
of quail harvested by hunters had insecticide residues in their bodies.
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
Granular Insecticides
Granular formulations of
insecticides are a real hazard to birds. Birds eat granules exposed on the soil
surface, mistaking them for food or grit. Just a few granules may be enough
to kill a small bird, such as a quail. Whenever granular formulations are used,
the hazard to wildlife can be reduced by fully incorporating the granules into
the soil. It is especially important to disk under granules spilled at row ends
where birds are likely to search for food
To reduce the danger to wildlife from granular formulations:
Liquid Insecticides
The danger to wildlife
of liquid formulations of insecticides depends mainly on their toxicity and
use. The toxicity of foliarapplied insecticides to wildlife range from low to
high. Methyl parathion, azinphosmethyl (Guthion), disulfoton (DiSyston),
and dimethoate (Cygon) are highly toxic to wildlife and are known to have caused
wildlife death. Methomyl (Lannate) is also highly toxic to wildlife but has
not been reported to cause wildlife mortality.
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:
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.
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. Ultralowvolume sprays
are more likely to cause drift than lowpressure sprays. Finally, never
spray when the wind is blowing faster than 8 mph.
Fungicides
Fungicides used in small
grain fields and sorghum fields include foliar sprays and seed treatments. Fungicides
currently used on small grains and sorghum have a low toxicity to birds and
mammals and do not present a hazard to wildlife. Some fungicides are toxic to
fish; they include mancozeb (Dithane M45, Penncozeb, Manzate 200). Triadimefon
(Bayleton) and propiconazole (Tilt) are only moderately to slightly toxic to
fish.
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 AG4197,
Small Grain Production Guide No. 7, Disease
Management.
Herbicides
Most herbicides used during
small grain production are only slightly toxic to wildlife. One exception is
paraquat (Gramoxone), which is moderately toxic to birds and can cause abnormal
growth of embryos in some bird eggs. Waterfowl eggs are particularly sensitive
to paraquat. Generally, however, herbicides do not directly affect wildlife.
More often, herbicides affect wildlife by damaging their habitats.
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 twoyear 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. Costsharing programs are available to develop filter strips.
Filter strips also protect water quality by reducing runoff of pesticides and
soil.
Table 1.Toxicity of Pesticides Used on Small Grains to Birds, Mammals, and Fish
| Pesticide (Brand Name) | Birdsa | Mammalsa | Fishb |
| azinphosmethyl (Guthion | HC | H | EH |
| carbaryi (Sevin) | L | L | M |
| carbofuran (Furadan) | HC | H | H |
| chlorpyrifos (Lorsban) | H | L | EH |
| dimethoate (Cygon) | HC | M | M |
| disulfoton (DiSyston) | HC | H | H |
| malathion | L | L | EH |
| methomyl (Lannate) | H | H | H |
| methyl parathion | HC | H | H |
aWildlfie hazard is based on the following toxicities:
H (Highly toxic) LD50 less than 30 mg\kg and LC50 less than500 pprn.
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 pprn.
L (Low toxicity) LD50 greater than 100 mg/kg and LC50 greater than 1,000 pprn.
NT (not toxic)
bFish 96 hour LC50 toxicities are as follows:
EH (Extremely toxic) less than Q 1 pprn
H (Highly toxic) 0.1 to 1.0 pprn
M (Moderately toxic) 1 to 10 pprn
L (Low toxicity) greater than 10 pprn
To convert fish toxicities
to pounds of active ingredient per acre foot of water. multiply by 2.7.
cActive ingredient
(not necessarily a specific product) has caused wildlife deaths.
TABLE 2. Hazard of Insecticides Used on Small Grains and Sorghum to Wildlife
Insect |
Insecticide (Brand Name) |
Wildlife
hazarda |
Killsb |
Comments |
| Insect Control in Small Grains | ||||
| Aphids | disulfoton(DiSyston)
dimethoate (Cygon) encapsulated methyl parathion (PenncapM) methyl parathion malathion |
high high moderate high low |
yes yes no yes no |
Methyl parathion
is toxic to bees. Malathion is the safest material for wildlife. Disulfoton is less hazardous when applied directly to soil. |
| Cereal leaf beetle | azinphosmethyl(Guthion)
carbaryl (Sevin) encapsulated methyl parathion (PenncapM) malathion methomyl (Lannate) |
high low moderate low moderate |
yes no no no no |
Methylparathion
is toxic to bees. Azinphosmethyl and methomyl are toxic to wildlife. Sevin and malathion are safer for wildlife. |
| Fall armyworm | methomyl (Lannate) | moderate | no | Treat only
when IPM thresholds are exceeded. |
| True armyworm | carbaryl
(Sevin) encapsulated methyl parathion(PenncapM) methomyl (Lannate) methyl parathion trichlorfon (Dylox, Proxol) |
low moderate moderate high low |
no no no yes |
Carbaryl
and trichlorfon are safest for wildlife. Best results occur when temperatures are warm and caterpillars are active. |
| Insect Control In Sorghum | ||||
| Aphids | dimethoate
(Cygon) malathion |
high low |
yes no |
Malathion
is safer than di methoate. |
| Cinch bug | carbaryl (Sevin) | low | no | |
| Corn earworm
Fall armyworms Webworms |
carbaryl
(Sevin) chlorpyrifos (Lorsban) methomyl (Lannate) |
low moderate moderate |
no no no |
toxic and
care should be , taken to avoid drift of materia into wildlife habitats. |
| Sorghum midge | carbaryl (Sevin) | low | no | Carbaryl
has low toxicity to most birds and mammals. |
aWildlife
hazards:
high indicates possible wildlife deaths;
moderate indicates possible wildlife sickness, deaths less likely;
low indicates sickness unlikely.
bKills:
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 TipsTo Protect Fish and Wildlife Resources