Arboriculture & Urban Forestry 43(6): November 2017 killed proportionately more late instars within 48 hours (Fisher’s exact test, P < 0.001; Figure 2A). Both treatments rapidly reduced frass produc- tion, indicating cessation of feeding (Figure 2B). 249 Eastern tent caterpillar on crabapple One-day-old residues of chlorantraniliprole or spinosad gave comparable control of early instar ETC (second and third instar); each significantly reduced survival, frass produc- tion, and defoliation within 24 hours (Table 2). Field-weathered 14-day-old residues of both insecticides also reduced survival and frass production by later (mostly fourth) instars, and chlorantraniliprole also sup- pressed the amount of defoliation caused rela- tive to cohorts in untreated leaves (Table 2). Roseslug sawfly on rose Field-weathered dry residues of chlorantra- niliprole on rose foliage killed roseslug sawfly larvae and prevented feeding damage for at least 14 and 21 days, respectively, signifi- cantly longer than did carbaryl (Figure 3A). Although only about 20% of the larvae on leaves with 21-day-old chlorantraniliprole residues were killed outright, survivors’ feed- ing was completely shut down (Figure 3B). Figure 2. Mortality and frass production (indicative of feed- ing) of cohorts of mid-sized (mostly fifth instar) or large (mostly seventh instar) evergreen bagworms 48 hours after confinement on arborvitae shoots with dry residues of chlorantraniliprole (Chlor) or Bacillus thuringiensis var. Kurstaki (Bt) compared to cohorts on untreated checks (UTC). Upper graph: Both treatments controlled mid-sized larvae but chlorantraniliprole was more effective against late instars (Fisher’s exact test, see text). Lower graph: Both treatments reduced frass production indicating cessation of feeding (F2,77 = 223, F2,67 = 43.1) for mid-sized and large larvae, respectively; both P < 0.001; within size classes, means topped by same letter are not significantly different (LSD, P = 0.05). Lace bugs, aphids, and soft scale crawlers Foliar sprays of chlorantraniliprole were ineffec- tive for residual control of hawthorn lace bugs (Figure 4). In contrast, 1- and 7-days-old resi- dues of bifenthrin gave 95% and 47% control, respectively, relative to mortality in the untreated check (Figure 4A). Chlorantraniliprole sprays also failed to curatively control oleander aphids on swamp milkweed seedlings, whereas bifen- thrin sprays gave >99% control (Figure 4B). Spraying oak twigs and leaves with chlorantra- niliprole near the end of crawler hatch and during crawler settlement did not significantly reduce Table 2. Efficacy of 1- or 14-day-old field-weathered residues of chlorantraniliprole or spinosad for control of early or late instars of the eastern tent caterpillar (Malacosoma americanum) on black cherry foliage. Treatmentz Chlorantraniliprole Spinosad Untreated One-day-old residues versus early instarsy No. surviving (of 10) 2.4 ± 1.2 a 1.6 ± 1.4 a 10.0 ± 0.0 b Frass rating 3.2 ± 0.4 b 2.2 ± 0.4 a 5.0 ± 0.0 c Leaf area eaten (cm2 2.0 ± 0.4 a 1.8 ± 0.5 a 4.6 ± 0.9 b tively. Means (±SE) not followed by the same letter differ significantly (LSD, P < 0.05). x z Rates as in Table 1. Trials were evaluated 24 hours aſter larvae were introduced. y Larval cohorts consisted of second and third instars. ANOVA: F2,12 14-days-old residues versus late instarsx No. alive ) (of 5) 2.6 ± 0.4 b 1.0 ± 0.3 a 4.6 ± 0.4 c Larval cohorts consisted of four fourth instars and one third instar. ANOVA (late instar data): F2,12 frass, and area eaten, respectively. Means (±SE) not followed by the same letter differ significantly (LSD, P < 0.05). Frass rating 3.6 ± 0.2 a 3.8 ± 0.2 a 4.8 ± 0.2 b Leaf area eaten (cm2 36 ± 5 a 46 ± 11 ab 72 ±10 b = 19.4, 21.6, 6.1; P < 0.001, P < 0.001, and P < 0.015 for survival, frass, and area eaten, respec- = 23.2, 8.9, 4.1; P < 0.001, P < 0.001, and P < 0.05 for survival, ) ©2017 International Society of Arboriculture
November 2017
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