Integrated pest management (IPM) should be the basis for all management decisions regarding pests. IPM is a sustainable approach to managing pests. It combines biological, cultural, physical, and chemical control tools that minimize economic, health, and environmental risks. Nonchemical pest management methods, such as resistant varieties, natural biological control, timely tillage and planting, and others, are beneficial in reducing pest status and abundance. The use of these methods always should be considered in developing a sound IPM program. A good IPM program will balance all risks in selecting appropriate control strategies. When pesticides are necessary, economic risks can be minimized by using appropriate pest scouting techniques and economic thresholds (ET) to make pest management decisions. Health risks can be minimized by following all safety directions provided on pesticide labels. Environmental risks can be minimized by avoiding pesticide use when possible, selecting the most appropriate pesticide for each situation, and following all environmental and wildlife safety guidelines on the pesticide label.

In the past, early-planted, short-season corn in the Corn Belt was most attractive to moths that produced first-generation European corn borers. These plantings often were damaged severely. Early-planted corn escaped the second generation because the maturing plants were no longer attractive for egg laying. However, late-planted, short-season corn was highly attractive for egg laying because of its immaturity; consequently, it sustained large numbers of second-generation European corn borer.

Currently, there is a trend to plant long-season corn with heavy fertilization. When planted early, this corn can be attacked by the first generation and may still be attractive to the second generation. This is particularly true in areas of the Corn Belt where irrigation is available and used throughout the growing season; the period for succulent plants is extended. Corn hybrids planted in these areas are usually long-season, planted very early, and planted at a higher population than their neighboring nonirrigated corn fields.

If weather favors larval survival when long-season corn is grown, it may be necessary to treat the field for more than one generation. When light traps or pheromone traps show heavy moth flight and corn is shedding pollen, green silks are present, or the ear is in the milk stage, treatment may be needed to control the second or third generation, depending on the latitude.

To apply economic injury levels and economic thresholds to the European corn borer, the concept of a treatment "window" must be understood. Only larvae that have not bored into the plant can be killed. Consequently, between the time eggs hatch and the time larvae bore into the plant, there is a specific period, or window, when pesticides must be applied to be effective. Egg deposition in a given field may last 3 weeks. Insecticides kill larvae over a relatively short period of time; therefore, they must be applied before all eggs are deposited. If the treatment is delayed, larvae from eggs deposited early in the egg-laying period will enter the plant and will not be controlled effectively by the insecticide. The decision to treat should be based on an estimate of the potential European corn borer population density expected to become established within the stalks.

Timing is one of the most critical aspects of controlling the European corn borer with insecticides. The number and timing of whorl-stage treatments depend on infestation severity and the degree of control desired. For a single application, an insecticide should be applied from 10 to 14 days after initiation of egg laying, which would be 0 to 4 days after the peak. One treatment is usually sufficient on field corn during the whorl stage of corn development, except with very heavy infestations. If two applications are needed for one generation, the first should be applied at 40 to 50 percent completion of egg laying (9 or 10 days after initiation of egg laying), and the second should be applied about 7 days later. Seed corn or other high-value crops may profitably receive two or more treatments. Note any re-entry pesticide label restrictions that advise against rescouting the field without adequate protective equipment.

Various procedures have been advocated to determine application time for control on whorl-stage corn. Some of these procedures have included measuring the percentage of moth emergence and accumulated egg masses per 100 plants. However, percentage fresh whorl feeding and the presence of live larvae in the whorl have proven to be the best criteria for treatment timing. Control can be effective as long as the majority of larvae are in the whorl. Once larvae migrate from the whorl and enter the stalk, control is virtually ineffective. See the previous section for determining cost versus benefit (Table 5) in whorl-stage corn. Treatment after larvae have invaded the stalk will not be satisfactory.

Intensive scouting is necessary to determine application time for control during the tasseling and pollen-shedding stage of corn development. Without scouting and development of an economic threshold for suspect fields, control of the second- or third-generation European corn borer is more difficult. More than one insecticide application may be necessary. The first application should be applied to the corn field when eggs begin to hatch and before larvae begin to bore into leaf midrib, sheath, and collar tissues (see Table 1). Choose an insecticide that will control newly hatched larvae for several days and provide suitable control with one application (Table 7 below). Nonresidual insecticides do not provide control during corn tasseling and silking. If fresh eggs are still observed 7 to 10 days following the first application, a second treatment may be necessary, depending on egg density, presence of live larvae, and a new economic threshold determination. Larvae in the ear tip, sheath, and collar area of field corn cannot be controlled by an insecticide application (see Sweet Corn).

Table 7. Yield increases from five different corn fields receiving one insecticide application for second-generation European corn borer in Iowa (M. E. Rice).

                     Actual         Bushels per acrea
                     ingredient ------------------------------
Year  Insecticide    per acre   Treatedb  Untreated  Increasec
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1991  Penncap-M      0.75       170.5     137.9      32.6
1992  Dyfonate 20G   1.00       200.0     193.1      6.9
1992  Penncap-M      0.75       209.1     199.9      9.2
1993  Pounce 3.2EC   0.15       124.7     115.3      9.4
1993  Lorsban 15G    1.00       113.9     99.2       14.7
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^aYields were taken with a four- or six-row combine and were adjusted to 15.5 percent moisture.
^bTreatments were replicated two to four times in each field.
^cAll yield increases are significantly larger than the untreated check (P = 0.1, FLSD).