Certified Professional Horticulturist (CPH) Practice Exam

Which of the following are common causes of plant disease on interior plants?

1. Low temperature and artificial light

2. Low light and too frequent watering

3. Aphids and scales

4. Mealybugs and ladybugs

The correct answer is: Low light and too frequent watering

Low light and too frequent watering are significant factors that contribute to plant disease in interior plants. Indoor environments often have limited natural light, which can inhibit a plant's ability to photosynthesize effectively. Insufficient light can weaken plants, making them more susceptible to diseases. Additionally, overwatering is one of the most prevalent issues with indoor plants, leading to root rot, fungal growth, and other conditions that compromise plant health. When a plant is consistently overwatered, the roots can suffocate due to lack of oxygen, creating an environment conducive to pathogens. In contrast, low temperature and artificial light may cause stress to plants but are not as directly linked to causing diseases. Aphids and scales are pests that can lead to plant stress and secondary infections, but they are not causes of disease themselves. Similarly, mealybugs are pests that harm plants, while ladybugs are beneficial insects that help control pests; therefore, they are not a cause of disease. The focus on low light and overwatering encompasses the critical cultivation practices that can lead to plant disease.