. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. AGRICULTURAL LANDS The European corn borer has been an important pest in Illinois since it migrated to the state more than 50 years ago. The average annual loss of corn grain due to corn borer in Illinois was estimated in the 1980s at $50 million. Figure 29 shows the pattern of population fluctuations over the state since 1943. Generally, more than two corn borers remaining in a stalk during the fal
. The changing Illinois environment : critical trends : technical report of the Critical Trends Assessment Project. Man; Pollution; Environmental protection; Ecology; Environmental impact analysis. AGRICULTURAL LANDS The European corn borer has been an important pest in Illinois since it migrated to the state more than 50 years ago. The average annual loss of corn grain due to corn borer in Illinois was estimated in the 1980s at $50 million. Figure 29 shows the pattern of population fluctuations over the state since 1943. Generally, more than two corn borers remaining in a stalk during the fall sampling period represent damaging populations in Illinois corn fields. Of course, when the average for the state is near two per stalk, many fields have many more than the average. Figure 29 demonstrates that the corn borer populations have not declined during the past 10 years. The gypsy moth is a serious defoliator of urban and forest trees in the northeastern United States. In Illinois, the moths have been trapped off and on over the past 20 years, usually in very low numbers. Most have been caught in the northeast part of the state around Chicago (Figure 30). This pest may be estab- lished in this area or the traps may be picking up male moths that have flown far away from areas infested by flightless females. The values in Figure 30 are lower than those found in the heavily infested areas in the Northeast. Based on 1992 trapping, 18 sites comprising 400 acres required treatment in 1993. To establish a viable population, female and male larvae must slowly enter a new region along an invasion front. The wave of infestation is currently moving through Michigan (Figure 31). This wave is expected to reach Shawnee National Forest in southern Illinois in the year 2000. A faster means of migration over long distances can occur when the gypsy moth hitches rides on motorized vehicles that have passed through infested areas. Thus, a recreational vehicle that leaves Michigan in Jul
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