Yellows are due to various causes, including lack of soil nutrients, crown or root rot, insects, fungi, and viruses. Virus-yellows cause plants to be stunted and to have yellow, bunchy growth. Flowers may be greenish, aborted, or lacking altogether.
Yellows occur frequently on asters, chrysanthemums, lettuce, and carrots. Control by using healthy plants and by limiting insects and weeds. Use crop rotation and destroy infected plants.
