Certified Professional Horticulturist (CPH) Practice Exam

Overapplication of which plant nutrient is likely to increase sucking insect problems?

1. Nitrogen

2. Potassium

3. Phosphorus

4. Calcium

The correct answer is: Nitrogen

Overapplication of nitrogen is likely to increase sucking insect problems due to its impact on plant growth and health. When nitrogen levels are excessively high, plants tend to exhibit lush, rapid growth, resulting in tender, succulent tissues. These tender tissues are highly attractive to sucking insects, such as aphids and whiteflies, which thrive on the nutrient-rich, soft plant material. Additionally, excessive nitrogen can lead to imbalances in other nutrients and can make plants more susceptible to stress and disease, further exacerbating pest problems. In contrast, potassium, phosphorus, and calcium play different roles in plant health and are less directly associated with the attraction of sucking insects. Potassium, for example, helps with overall plant vigor and stress resistance and can actually help fortify plant tissues against pests. Phosphorus is crucial for root development and energy transfer, while calcium is important for cell wall structure and overall plant stability, neither of which primarily impacts the attractiveness of plants to sucking insects.