Work sheet for Second Generation European
Corn Borer Larvae

Notes: This work sheet only takes into consideration physiological yield losses, not losses due to stalk breakage or ear drop. There are many factors that affect yield loss, such as moisture stress, corn hybrid, and the percent of eggs deposited at the time of scouting. This work sheet is intended to provide general advice on treatment feasibility; it is best to perform further analysis, especially in cases where the economic benefit of treatment is marginal.
   Please type your name:
Default Values*
   A.  Survival rate:   %
   B.  Percent control of corn borer by chemical treatment:  %
   C.  Plant stage at time of scouting:   Silking     Blister     Dough     Dent    
      Note: If plants are at "dent" stage during scouting, there is no need for treatment
Actual Data Sample Data
   1. Yield potential for this field:    Bushels/acre 150   
   2. Estimated price/bushel: $   Price/bushel $   3.50   
   3. Adjusted average number of egg
       masses per plant:		    Egg masses/plant 0.25   
   4. Cost of chemical: $   Cost of chemical/acre $  7.50   
   5. Cost of application: $   Cost of app./acre $  8.00   

*Hints or Explanation for Each Question
A. On average, about 15% of the larvae in an egg mass survive to form a cavity in the plant stem. Survival could be higher or lower depending on environmental conditions.
B. 70% is an average estimate of second generation corn borer control.
C. Choose "Silking" for plants that are silking, or not yet silking. Silking corresponds to a 4% loss per larvae; Blister to a 3% loss, Dough to a 2% loss; and Dent to no loss.
1. What is the expected yield, in bushels per acre?
2. How much do you expect to sell each bushel for?
3. The recommended scouting area of each plant includes the ear leaf, three leaves below and three leaves above. This will find 90% of the egg masses; so you need to increase the average egg masses found per plant by 10% (mulitply the average by 1.10). For example, if 100 plants are examined and 38 egg masses found, the average egg mass found per plant is 0.38, but this is multiplied by 1.10 to adjust for egg masses missed by not counting every leaf. So the adjusted average would be (.38)*(1.10) = .42.
4. What is the cost of the chemical, per acre?
5. What does it cost (per acre) to apply the chemical?