What size orifice should be used if the current herbicide application results in a double rate?

Using a smaller orifice is appropriate if the current herbicide application results in a double rate. This adjustment is necessary to reduce the volume of herbicide being discharged, ensuring that the application rate aligns with the intended dosage. A smaller orifice will create less flow, effectively lowering the application rate per unit area. By decreasing the orifice size, it helps to minimize the risk of overapplication, which can lead to potential damage to non-target species and adverse environmental impacts.

The other options suggest changes that could either maintain the current application rate or increase it, which would not be advisable if the goal is to correct an over-application situation. Therefore, selecting a smaller orifice provides a practical solution to achieve the desired herbicide application rate effectively.