. Boll weevil suppression, management, and elimination technology : proceedings of a conference, February 13-15, 1974, Memphis, Tennessee. Boll weevil, Control, Congresses. 1971 1972 1973 Figure 5.—Seasonal average Heliothis spp. larval densi- ties in cottonfields in the eradication area and in a normal treated area. Lygus: x 3000 09 u2000 < 1000. 1971 1972 1973 Figure 6.—Seasonal average densities of Lygus lineo- laris in cottonfields in the eradication area and in a normal treated area. tion area and the situation reversed itself. Popu- lations were higher in the no-insecticide eradica- t
. Boll weevil suppression, management, and elimination technology : proceedings of a conference, February 13-15, 1974, Memphis, Tennessee. Boll weevil, Control, Congresses. 1971 1972 1973 Figure 5.—Seasonal average Heliothis spp. larval densi- ties in cottonfields in the eradication area and in a normal treated area. Lygus: x 3000 09 u2000 < 1000. 1971 1972 1973 Figure 6.—Seasonal average densities of Lygus lineo- laris in cottonfields in the eradication area and in a normal treated area. tion area and the situation reversed itself. Popu- lations were higher in the no-insecticide eradica- tion area (about 1,400/acre) than in normal area where in-season insecticides were used (about 750/acre). Geocoris (fig. 2) and spiders (fig. 3) and other predator groups showed similar patterns during the 3-year period. A summary of effects on all predators is shown in figure 4. The 1971 predator density was approximately 300/acre in both areas. In 1972, under heavy insecticide pressure, the predator population in the eradica- tion area was approximately 2,000/acre, or ap- proximately 40 °/o as high as the population den- sity of approximately 5,000/ acre in the "normal" area. These data also indicated a reversal of the situation in 1973, when under no insecticides the predators recovered and their populations were approximately 36% higher than in the "normal" area. The summary data of the Heliothis popula- tions (fig. 5) show an inverse relationship to the predator populations. In 1972, under heavy insecticide pressure, the Heliothis population was much higher in the eradication area than in the "normal" area, while in 1973, under no insecticide pressure, Heliothis populations were lower in the eradication area than in the insecti- cide-treated "normal" area. These data support our hypothesis that under no in-season insecticide regimes, the natural enemies of Heliothis spp. will regulate popula- tion fluctuations within levels consi
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