Cost:Benefit Analysis Chart for First Generation European Corn Borer

Table 14. Cost:Benefit Analysis Chart for First Generation European Corn Borer

____ larvae/100 plants	X 0.2 survival^a	= ___ surviving larvae
____ surviving larvae	÷ 100 plants examined	= ___ larvae/plant
____ larvae/plant	X ____ yield reduction/larva^b	= ___ yield reduction
____ yield reduction	X ____ bushels/A	= ___ bushels loss/A
____ bushels loss/A	X ____ per bushel value	= ___ loss/A
____ loss/A	X ____ proportion control^c	= ___ preventable loss/A
____ preventable loss/A	X ____ cost of control/A	= ___ profit (or loss)/A
^{Cost:Benefit Ratio _________ Economic injury level __________}

Survival of larvae from the first and second instar to the fourth and fifth instars that bore into the plant is estimated to be about 20%. However, survivorship can be as high as 50% or as low as 1%.

Yield loss from European corn borer varies with plant growth stage:
10th leaf stage = 0.059, 16th leaf stage = 0.05 and Pollen Shed = 0.04.

Average proportional control of first generation European corn borer using an insecticide is about 0.72. However, it can vary between 0.50 to 0.90 depending on the product and timing.

Example Calculation

300 larvae/100 plants	X 0.2 survival	= 60 surviving larvae
60 surviving larvae	÷ 100 plants examined	= 0.6 larvae/plant
0.6 larvae/plant	X 0.059 yield reduction/larva	= 0.035 yield reduction
0.035 yield reduction	X 135 bushels/A	= 4.73 bushels loss/A
4.73 bushels loss/A	X $3.00 per bushel value	= $14.18 loss/A
$14.18 loss/A	X 0.72 proportion control	= $10.21 preventable loss/A
$10.21 preventable loss/A	X $15.00 cost control/A	= $4.79 profit (or loss)/A

Cost:Benefit Ration = $15.00/A/$10.21/A = 1.47
(does not pay to implement control)

Economic injury level = 0.88 larvae per plant