Southeastern U.S. Vegetable Crop Handbook - 2022 - 147

TOXICITY OF CHEMICALS USED IN PEST
CONTROL
The danger in handling pesticides does not depend exclusively
on toxicity values. Hazard is a function of both toxicity
and the amount and type of exposure. Some chemicals are very
hazardous from dermal (skin) exposure as well as oral (ingestion).
Although inhalation values are not given, this type of exposure
is similar to ingestion. A compound may be highly toxic
but present little hazard to the applicator if the precautions are
followed carefully.
Toxicity values are expressed as acute oral LD50
milligrams of the substance per kilogram (mg/kg) of test animal
body weight required to kill 50 percent of the population. The
acute dermal LD50
is also expressed in mg/kg. These acute values
are for a single exposure and not for repeated exposures such
as may occur in the field. Rats are used to obtain the oral LD50
and the test animals used to obtain the dermal values are usually
rabbits.
CATEGORIES OF TOXICITY1
Categories
I
II
III
IV
1 EPA accepted categories.
2
Signal Word
Danger-Poison
Warning
Caution
None2
LD50 Value (mg/kg)
Oral
0 - 50
50-500
500-5,000
5,000
Dermal
0 - 200
200-2,000
2,000-20,000
5,000 20,000
No signal word required based on acute toxicity; however, products in this
category usually display " Caution. "
Read all labels and become familiar with the symptoms
of pesticide poisoning. For help in a pesticide emergency,
seek immediate medical attention and call the appropriate
poison information number on the back cover of this book.
TOXICITY AND LD50 CALCULATIONS WEIGHT
CONVERSIONS
1 ounce (oz) = 28 grams (gr)
1 pound (lb) = 454 grams (gr)
1 gram (gr) = 1,000 milligrams (mg)
1,000 mg = 0.035 oz
1 mg = 0.000035 oz
CONVERSIONS: BODY WEIGHT IN POUNDS (LB)
TO BODY WEIGHT IN KILOGRAMS (KG)
(lb)
(kg)
25 = 11.25
50 = 22.5
75 = 33.75
100 = 45
To determine an exact weight, multiply known body weight
in pounds by 0.45. Example: 100 lb x 0.45 = 45 kg
Note: All the following calculations use a body weight of
100 pounds. To determine the LD50
kilograms; to do this multiply weight in lb by 0.45.
Example: 100 x 0.45 = 45 kg
2022 Vegetable Crop Handbook for Southeastern United States
147
CONVERSION INFORMATION FOR USE
OF PESTICIDES ON SMALL AREAS
LIQUID MATERIALS
Recommended
Rate per acre
1 pint
1 quart
2 quarts
1 gallon
25 gallons
50 gallons
75 gallons
100 gallons
Approximate Rate
per 1,000 sq. ft.
¾ tablespoons
1½ tablespoons
3 tablespoons
6 tablespoons
4½ pints
8 pints
7 quarts
9 quarts
Approximate Rate
per 100 sq. ft.
¼ teaspoon
½ teaspoon
1 teaspoon
2 teaspoons
1 cup
1 pint
1½ pints
1 quart
For dry materials, such universal conversions are not possible
because these materials vary widely in density. You can use
volume measurements such as teaspoons, tablespoons, and cups,
but you must first weigh a tablespoon of each product so that you
will know what volume measurement to use to obtain the desired
weight. Remember that there are 43,560 square feet in an acre.
To convert a per-acre rate to 1,000 square feet, divide the peracre
rate by 43.56. To convert a per-acre rate to 100 square feet,
divide the per-acre rate by 435.6.
, first convert body weight to
Example: A rate of 2 pounds of Dithane DF per acre is desired
for a planting of 1,000 square feet. Divide the per-acre rate of
907 grams (453.6 grams per pound) by 43.56 to get 20.8 grams.
Since Dithane DF weighs about 10 grams per tablespoon, you
would need two tablespoons. Knowing the weight per tablespoon
for each product you work with, you can use a tablespoon for
measuring, rather than weighing.
Insecticide
Furadan
Herbicide
Micro-Tech/Partner
Fungicide
Chlorothalonil
Next, multiply given LD50
Note: LD50
by body weight in kg.
numbers are given by the manufacturer.
Example: LD50 of 11 x 45 kg = 495 mg
Next, to convert milligrams (mg) to ounces (oz), multiply
mg by 0.000035. Example: 495 mg x 0.000035 = 0.017 oz.
The following is a chart of LD50
in terms of
figures converted to ounces for
three commonly used products in the agricultural industry.
Body Weight in Pounds
LD50
11
1,800
10,000
30
0.005
0.9
4.9
60
0.010
1.7
9.5
100
Ounces
0.017
2.8
15.7
0.026
4.3
23.8
0.035
5.7
31.5
150
200
Southeastern U.S. Vegetable Crop Handbook - 2022

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