What is Begonia Aster Yellows Disease?
Aster yellows disease on begonias is caused by a phytoplasma (formerly referred to as a mycoplasma) that is spread by leafhoppers. This bacterium-like organism causes virus-like symptoms in a huge host range of more than 300 plant species in 48 plant families.
Symptoms of a Begonia with Aster Yellows
The symptoms of aster yellows vary depending upon the host species combined with the temperature, age, and size of the infected plant. In the case of aster yellows on begonias, the first symptoms appear as chlorosis (yellowing) along the veins of young leaves. The chlorosis worsens as the disease progresses, resulting in defoliation. Infected plants do not die or wilt but, instead, maintain a rather spindly, less than robust growth habit. Aster yellows may attack part or all of the plant.
Begonia Aster Yellows Control
Aster yellows overwinters on infected host crops and weeds as well as in adult leafhoppers. Leafhoppers acquire the disease by feeding on the phloem cells of infected plants. As early as eleven days later, the infected leafhopper can transmit the bacterium to plants it is feeding on. Throughout the lifecycle of the infected leafhopper (100 days or longer), the bacterium multiplies. This means that as long as the infected leafhopper lives, it will continuously be able to infect healthy plants. The bacterium in the leafhoppers can be quelled when temperatures surpass 88 degrees F. (31 C.) for 10 to 12 days. This means that hot spells lasting for more than two weeks reduce the chances of infection. Since weather cannot be controlled, another plan of attack must be followed. First, destroy all susceptible overwintering hosts and destroy any infected plants. Also, remove any weed hosts or spray them prior to infection with an insecticide. Place strips of aluminum foil between the begonias. This is said to aid in control by disorienting the leafhoppers with the reflection of the light playing against the foil.
