First generation fourth stage (L4) larvae were also collected in 1992 from the four orchards. A total of 30 to 40 individuals was dosed topically (on the leaf in which they were feeding) at the same seven concentrations as used on the adult females. Mortality was assessed after 24 (LD50 values were determined in the same way as described above). Results: The results for chlorpyrifos are reported (see Table 1). The most sensitive LD50 value is 1.6 ng/individual for first generation adult males (from a site with no known insecticidal use). Table 1. LD50 Values for Topical Dosing with Chlorpyrifos for A. orana Sampled from Apple Orchards in Kent, England. LD50 (95% C.I.) INSECTICIDE SITE YEAR (ng LIFE STAGE MANAGEMENT a.i./individual) 1992 6.8 (5.4 8.1) – First generation 1994 12.0 (8.4 17.0) – males 1995 18.2 (14.4 22.9) – Loyterton Farm Intensive Second generation 8.2 (7.2 9.2) – males Second generation 1992 12.5 (10.8 14.4) – females 12.9 (11.4 14.6) L4 larvae – First generation 6.7 (5.8 7.6) – males Second generation 6.3 (5.4 7.0) – Farm 1992 Intensive Second generation 15.0 (13.0 17.5) – females 14.8 (12.1 18.1) L4 larvae – 1994 13.6 (8.7 19.2) – First generation Farm Intensive males 1995 23.2 (18.2 29.6) – generation 2.0 (1.2 2.6) – males Second generation 3.0 (3.2 3.7) – Littlebourne Court males 1992 None Second generation 4.3 (3.4 5.1) – females 4.4 (3.2 5.4) L4 larvae – 1992 1.6 (0.8 2.3) – First generation males 1994 6.8 (3.6 10.4) – Congelow Farm Second generation None 1.9 (0.8 2.8) – males Second generation 2.1 (1.0 3.1) – females
First generation fourth stage (L4) larvae were also collected in 1992 from the four orchards. A total of 30 to 40 individuals was dosed topically (on the leaf in which they were feeding) at the same seven concentrations as used on the adult females. Mortality was assessed after 24 (LD50 values were determined in the same way as described above). Results: The results for chlorpyrifos are reported (see Table 1). The most sensitive LD50 value is 1.6 ng/individual for first generation adult males (from a site with no known insecticidal use). Table 1. LD50 Values for Topical Dosing with Chlorpyrifos for A. orana Sampled from Apple Orchards in Kent, England. SITE INSECTICIDE MANAGEMENT LIFE STAGE YEAR LD50 (95% C.I.) (ng a.i./individual) Loyterton Farm Intensive First generation males 1992 6.8 (5.4 – 8.1) 1994 12.0 (8.4 – 17.0) 1995 18.2 (14.4 – 22.9) Second generation males 1992 8.2 (7.2 – 9.2) Second generation females 12.5 (10.8 – 14.4) L4 larvae 12.9 (11.4 – 14.6) Farm Intensive First generation males 1992 6.7 (5.8 – 7.6) Second generation 6.3 (5.4 – 7.0) Second generation females 15.0 (13.0 – 17.5) L4 larvae 14.8 (12.1 – 18.1) Farm Intensive First generation males 1994 13.6 (8.7 – 19.2) 1995 23.2 (18.2 – 29.6) Littlebourne Court None generation males 1992 2.0 (1.2 – 2.6) Second generation males 3.0 (3.2 – 3.7) Second generation females 4.3 (3.4 – 5.1) L4 larvae 4.4 (3.2 – 5.4) Congelow Farm None First generation males 1992 1.6 (0.8 – 2.3) 1994 6.8 (3.6 – 10.4) Second generation males 1.9 (0.8 – 2.8) Second generation females 2.1 (1.0 – 3.1)
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