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Economic Injury Levels of the Red Sunflower Seed Weevil, |
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Economic Injury Levels of the Red Sunflower Seed Weevil, |
Economic injury level (EIL) of the red
sunflower seed weevil on oilseed sunflower can be calculated using the formula developed
by Peng and Brewer (1995) of North Dakota State University:
EIL as number of seed weevils per flower = [cost of
control per acre ÷ market value
of oilseed sunflower per pound] ÷ [loss per insect].
Make sure that the market value is expressed on a $ per pound basis and not on the usual $ per 100 pound basis.
Loss per insect varies with plant population and are as follows: 12.38 (for 18,000 plants per acre), 13.33 (for 20,000 plants per acre), 13.80 (for 21,000 plants per acre), 14.28 (for 22,000 plants per acre), 14.75 (for 23,000 plants per acre), and 15.22 (for 24,000 plants per acre).
For example, the EIL for red sunflower seed weevil at $12 per acre insecticide plus application control cost, $0.07 per pound market value of oilseed sunflower, and 20,000 per acre plant population is:
EIL = [12 ÷ 0.07] ÷ [13.33] = about 13 red seed weevils per flower
EIL is the estimated breakeven point between the value of the damage that you are trying to prevent and the cost of controlling the insect.
Below is a table of calculated EILs in relation to varying costs of control and market values of oilseed sunflower and at 20,000 plant population:
| Market Value ($ per lb) |
Insecticide plus application cost ($ per acre) | |||||||
| 5.00 | 6.00 | 7.00 | 8.00 | 9.00 | 10.00 | 11.00 | 12.00 | |
0.06 |
6 |
8 |
9 |
10 |
11 |
13 |
14 |
15 |
0.07 |
5 |
6 |
8 |
9 |
10 |
11 |
12 |
13 |
0.08 |
5 |
6 |
7 |
8 |
8 |
9 |
10 |
11 |
0.09 |
4 |
5 |
6 |
7 |
8 |
8 |
9 |
10 |
0.10 |
4 |
5 |
5 |
6 |
7 |
8 |
8 |
9 |
0.11 |
3 |
4 |
5 |
5 |
6 |
7 |
8 |
8 |
0.12 |
3 |
4 |
4 |
5 |
6 |
6 |
7 |
8 |
0.13 |
3 |
3 |
4 |
5 |
5 |
6 |
6 |
7 |
0.14 |
3 |
3 |
4 |
4 |
5 |
5 |
6 |
6 |
0.15 |
3 |
3 |
4 |
4 |
5 |
5 |
6 |
6 |
