Ornamental and Turf Pesticide Applicators Practice Exam

Horticultural oils are most effective in controlling which of the following pests?

1. Caterpillars, whiteflies, and mealybugs

2. Mites, aphids, and armored scales

3. Thrips and spider mites

4. Adult beetles and locusts

The correct answer is: Mites, aphids, and armored scales

Horticultural oils are particularly effective in controlling pests such as mites, aphids, and armored scales due to their mode of action. These oils work by suffocating soft-bodied insects and disrupting their metabolic processes. When applied properly, horticultural oils coat the surface of these pests, blocking their breathing openings and leading to their eventual death. Mites and aphids have soft bodies, making them susceptible to oil applications, which can inhibit their feeding and reproduction. Armored scales are also effectively controlled by horticultural oils as the oil penetrates their protective coverings, allowing the active ingredient to reach them. In contrast, caterpillars, thrips, and adult beetles have more complex life cycles and tougher exoskeletons or feeding habits that make them less vulnerable to oil applications. For instance, caterpillars generally need different types of insecticides primarily aimed at targeting their digestive systems. Similarly, adult beetles and locusts have hard exoskeletons that provide them with greater resistance to suffocation from oil. Therefore, the specific effectiveness of horticultural oils aligns best with the pests listed in the correct answer, which are all known to be vulnerable to these types of treatments.