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Table 2. Parameter estimates [Equation 1] for the effects of herbicide rate and Leptinotarsa decemlineata population density on weed shoot biomass (standard errors in parentheses).
Herbicide Weed Herbivorya Cb D I50 b R2 RMSE Y90 FRR
g/plant g/plant g ae/ha g/plant g ae/ha
Fluroxypyr Volunteer potato 0 1.8 (0.7) 5.7 (0.8) 29 (11) 2.9 (2.7) 0.5 61 2.19 62
5 0.0 (>100) 4.2 (0.7) 8 (>100) 0.1 (10.2) 0.3 40 2.19 3
10 1.4 (0.3) 4.3 (0.4) 12 (>100) 18.7 (>100) 0.63 17 2.19 13
40 1.1 (0.1) 0.6 (0.3) 17 (38) 10.0 (>100) 0.23 5 2.19 0
Prometryn Volunteer potato 0 3.0 (1.1) 11.2 (1.6) 315 (99) 2.7 (2.4) 0.53 198 3.82 711
5 1.1 (2.0) 8.1 (0.9) 84 (>100) 0.9 (2.1) 0.67 66 3.82 139
10 1.7 (0.7) 4.0 (1.1) 40 (>100) 10.0 (>100) 0.13 113 3.82 31
40 0.8 (0.2) 2.3 (0.3) 15 (>100) 10.0 (>100) 0.53 7 3.82 0
Mesotrione Cutleaf nightshade 0 0c 4.1 (0.7) 12 (26) 0.3 (0.4) 0.56 25 0.82 >105
5 0 2.2 (0.5) 0.1 (2) 0.4 (1.1) 0.47 12 0.82
10 0 1.8 (0.4) 0.1 (2) 0.2 (0.6) 0.36 10 0.82
15 0 0.8 (0.3) 9 (76) 0.2 (0.8) 0.09 5 0.82
Fluroxypyr Hairy nightshade 0 0 8.2 (0.7) 30 (8) 1.2 (0.5) 0.69 29 1.64 187
5 0 7.7 (1.1) 24 (26) 0.5 (0.3) 0.48 59 1.64 >224
10 0 6.8 (0.4) 20 (11) 0.4 (0.1) 0.45 58 1.64 >224
15 0 6.5 (0.6) 4.2 (9.1) 0.4 (0.9) 0.76 20 1.64 >224

aHerbivory level is the number of Colorado potato larvae maintained on plants for the duration of trials.
bC is lower asymptote; D is upper asymptote; I 50 is herbicide rate eliciting 50% response; b is slope at I 50 rate; RMSE is root mean square error;
Y90 quantifies plant response that results in 90% reduction in the absence of herbivory; FRR quantifies the herbicide rate required to reduce the response variable to Y 90 .
cC was set to zero in two trials, reducing [Equation 1] to a 3-parameter model.
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