Which of the following is NOT a reason to avoid adding wetting agents?

The reason to avoid adding wetting agents that stands out is their role in enhancing herbicide efficacy, particularly when applied to crops. Wetting agents can improve the spreading and penetration of herbicides on plant surfaces, which can lead to better absorption and effectiveness. However, this can also have unintended consequences, especially if the target is non-selective.

Considering the other options, increased costs are a tangible factor that can deter the application of wetting agents—resources may be limited, and the additional expense could be unjustifiable in certain situations. Moreover, hard-to-wet crops, such as those with waxy or hairy surfaces, may not absorb herbicides as efficiently if wetting agents are not used, leading to suboptimal results. Also, when discussing weed susceptibility, while application strategies can indeed affect efficacy against weeds, the idea that they are "more susceptible" due to wetting agents does not align with the context of why one would avoid their use.

It's crucial to weigh these factors when making decisions on herbicide applications and understand the implications of using wetting agents in various agricultural scenarios.