Table 1: GR50 values for two ALS-inibiting herbicides and atrazine, Crop Sciences, Illinois

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Table 1: GR₅₀ values¹ for two ALS-inhibiting herbicides and atrazine determined for resistant
and susceptible smooth pigweeed biotypes 14 days after treatment.

Herbicide	1x Field Use Rate	Resistant GR₅₀	Susceptible GR₅₀	Resistance Ratio²
Herbicide	lb ai/A	lb ai/A	lb ai/A	R/S
Thifensulfuron	0.004	0.629	0.007	90
Imazamox	0.039	4.49	0.08	56
Atrazine	1.5	4	0.005	800
¹ GR₅₀ values represent the use rates required to achieve 50 percent reduction in plant growth. ² Resistance ratio provides an estimate of the level of resistance and is expressed as the resistant GR₅₀ divided by the susceptible GR₅₀.

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