|
|
|
Nursery & Forest
Volume 61 Number 5 Date 05/26/2016 CYLINDROSPORIUM LEAF SPOT - This fungal leaf spot disease was diagnosed on spirea 'Magic Carpet' nursery stock from Douglas County. Symptoms include light yellow leaf lesions that darken and coalesce over time, eventually forming large dead areas on the foliage of infected plants. Thorough sanitation and eliminating overhead irrigation are the recommended controls since CLS is spread by infected leaf litter and splashing water. TOBACCO RATTLE VIRUS - Recent nursery inspections in Iron and Oneida counties found tobacco rattle virus (TRV) on several Dicentra plants. This virus can be easily recognized on bleeding hearts by the bright yellow leaf discoloration it causes on normally green foliage. Tobacco rattle virus infects over 400 plant species, including ornamentals and agricultural crops such as potatoes. There is no treatment for this increasingly common virus and infected plants must be destroyed to prevent TRV from spreading. ROSE MOSAIC VIRUS - This viral disease, caused by a complex of prunus necrotic ringspot virus and apple mosaic virus, was found this month on roses in Price and Vilas counties. Rose mosaic virus (RMV) may not directly kill plants, but infected roses can exhibit small, distorted flowers, poor flower production, early autumnal leaf drop, and reduced vigor and hardiness. Symptoms include yellow or orange zig-zag banding on the foliage that are usually most pronounced during cool weather. Rose mosaic virus chlorosis is generally unlike nutrient deficiency and can be an effective visual diagnostic. This virus is thought to spread through the use of infected root stock, cuttings and scionwood, or possibly through rare natural root grafts. It is generally considered to be non-contagious in the field. Infected plants should be destroyed as there is no cure. GLOEOSPORIUM (AND RMV) ON ROSE - Several of the rose plants in the Price County nursery where rose mosaic virus was found were also infected with gloeosporium leaf spot, or rose anthracnose. Although leaf spot diseases like gloeosporium are usually not as damaging as viruses, they can cause severe defoliation and reduction in plant aesthetics and vigor. The occurrence of this and other fungal leaf spots can be minimized by limiting overhead watering practices, removing fallen diseased leaves and planting resistant varieties. HOSTA VIRUS X - Discounted hosta plants in Douglas County were showing characteristic symptoms of hosta virus X (HVX), namely irregular interveinal color-bleeding that causes hosta foliage to appear mottled and unhealthy. This incurable virus is easily spread via infected sap on cutting tools, and even by animal browsing. Infected plants should be disposed of in the garbage and not composted. -- Tim Allen, DATCP Nursery Inspector 
|
|