Which pesticide application method involves spraying directly onto plant leaves?

The method of applying pesticides that involves spraying directly onto plant leaves is known as foliar spray. This technique is specifically designed to target the foliage of plants, allowing for direct contact between the pesticide and the leaf surface. Foliar sprays are effective because they enable the active ingredients to be absorbed quickly through the plant's leaves, making it a common practice for controlling pests and diseases that affect the above-ground parts of plants.

In contrast, soil injection is a method where pesticides are injected into the soil around the plant’s root zone, which targets underground pests or delivers systemic action, but does not apply to the foliage. Bark spray refers to applying pesticides to the bark of trees, mainly to control pests that reside on or under the bark. Basal spray involves targeting the lower part of a plant's trunk or stem, often used to manage weeds or specific pests, but like bark spray, it does not involve the leaves directly. Thus, foliar spray stands out as the most appropriate method for the described application.