Why wouldn't you choose a granular if you were going to treat a tree or lettuce crop?

Choosing granules for treating trees or lettuce crops is often not ideal because granules are designed to be applied to the soil rather than directly to the foliage of plants. When treating crops like lettuce, which have a large leaf surface area, the application needs to ensure that the pesticide effectively adheres to the leaves for adequate coverage and absorption. Granular formulations typically do not adhere well to leaf surfaces, meaning that enough product may not reach the intended target areas.

Additionally, lettuce crops, being leafy vegetables, benefit from products that can effectively cover and penetrate the foliage. Liquid formulations, for instance, are better suited for this purpose as they can more easily coat the leaves and be absorbed. Thus, the efficiency and effectiveness of pest control would be compromised if granules are used in this context, which is why they are not the preferred choice for treating crops such as lettuce.

In contrast, the other options present concerns about cost, root harm, and permits that are less directly related to the primary function of pesticide application on foliage and may not apply in every scenario where granules could technically be used.