Managing scales infestation Scales are insects that have a remarkably severe effect on cannabis plants. An infestation will result in the plant showing stunted growth, and consequently very poor yields. Yellowing of the leaves is among the first signs of scale infestation. In very extreme and severe infestations, the plants wilt and eventually die off. Another symptom that the infected cannabis plants will show is the presence of a sticky substance known as honeydew. This substance creates the ...