Economic injury level (EIL) is the number of an insect pest on the field
that represents the breakeven point between the cost of control, and the
value of the damage on corn that could be prevented if a control action
is taken against the pest.

    Economic threshold (ET) is the number of an insect pest on the field that
represents the actual time at which control actions must be taken to prevent
the EIL from being reached and exceeded.

    If control measures can be taken without delay, then EIL and ET are one
and the same.  ET recognizes the fact that a lead time is usually needed
from the time damaging insect numbers are detected on the field to the
actual application of a control tactic.

    For most situations, it is recommended that ET be 80% of the EIL.

    Potential damage varies with the timing larvae infested the corn plants.
Corn is most susceptible just before tasseling when 7% yield reduction
may result per larva per plant.  Potential yield reductions by stage of plant
development infested are as follows (on a per larva per plant basis):    

    Use the First Generation ECB Threshold Worksheet developed by
the Department of Entomology at the University of Nebraska to help you
decide whether treating your field against first brood corn borers will be
profitable or not.  Use this worksheet also for univoltine corn borers.

    Use the Second Generation ECB Threshold Worksheet for the
second brood corn borers later in the season in areas with the bivoltine
moth flight.

These worksheets are interactive and quite easy to use.  Make sure to
give UNL credit whenever appropriate.

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                                                                         Prepared and posted  by Mike Catangui on June 19,  2000.
                                                                                                 Revised on 8-2-2000 by Mike Catangui.