Why may granules be an unsuitable choice for treating crops like trees or lettuce?

Granules may be an unsuitable choice for treating crops like trees or lettuce primarily because they do not adhere well to the leaves of these plants. When granules are applied, they tend to fall off or are washed away by rain or irrigation, reducing their effectiveness on the foliage where pests might be present. In contrast, pesticides that are formulated as liquids or sprays are designed to coat the leaves and ensure better contact with both the plant surface and any pests residing on it.

Additionally, factors like the plant structure, leaf surface characteristics, and the need for proper coverage are crucial when considering pesticide effectiveness for leafy crops. Since granules do not penetrate or cover the leaves adequately, this method may not provide sufficient control over pests that linger on the foliage.