Little cherry virus-2 is one of the causes of little cherry disease in western North America. It is transmitted by mealybug insects and causes smaller cherries, higher cull rates, and impacts color, shape, taste and flavor. While some varieties like Bing and Sweetheart can show reduced symptoms in subsequent years, fruit production and quality are never fully restored. Proper control involves managing mealybug vectors with insecticides, using virus-tested rootstock and budwood from certified nurseries, and promptly removing infected trees.

1. Little cherry virus -2 Facts and controls Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

2. Symptoms Small cherries Higher packing house cull percentage Negative impact on color, shape & taste 10.5 row Lambert & Royal Ann Little cherry virus -2 samples Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

3. Symptoms Bing & Sweetheart relatively tolerant Severe symptoms first year of infection Fruit size & color return to NEAR normal, but still reduced Fruit flavor never recovers Replace this picture with picture of Bings and/or Sweethearts with little cherry virus Little cherry virus-2 on ‘Sweetheart’ Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

4. Pathogen Little cherry disease can be caused by one of two agents Little cherry virus -1 Prevalent in Eurasia, but also with limited distribution in North America Insects that transmit this virus are unknown Little cherry virus -2 Most common form of the disease found in western North America Transmitted by at least one species of mealybug Western X disease appears similar Actually caused by special group of bacteria Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

5. Transmission Apple mealybugs spread the little cherry virus-2 Can be controlled with insecticide spray It is highly likely other types of mealybugs transmit the virus, but not confirmed Apple mealybugs Grape mealybugs Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

6. Transmission Transmitted via grafts of non-certified budwood or rootstocks Root grafting can pass virus on to healthy trees Best defense is to plant virus-tested trees from certified nurseries. Click here for a list of certified nurseries Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

7. Control Control mealybug vectors Control wild cherries (bitter cherry) near orchard Immediate & proper removal of infected trees Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

8. Proper tree removal As cut tree limbs start to dry, the insects (and viruses) may move to nearby trees. To prevent vector (and virus) movement. Apply good cover spray of broad spectrum insecticide/miticide to tree about 7 days before cutting. Goal: Prevent the spread of virus Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

9. Proper Tree Removal Or remove trees in winter while insects are dormant. Remove all of the wood from the orchard before mild spring weather. Even though Bing and Sweetheart trees can “bounce back” after virus infection, but they never return to full production. Healthy cherry tree surrounded by trees infected by little cherry virus-2. Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

10. Things to consider Even when you remove an infected tree, the virus may still be a threat Keep an eye on surrounding trees for the next 2 to 3 years If in doubt, have trees tested Newly infected tree may take 2-3 years to show symptoms Symptomatic tree to be removed Root graft

11. Things to consider Ignore the disease and it will continue to spread To nearby trees To your neighbors’ orchards Little cherry disease reduces economic viability of your orchard Decrease in yield Increase in culls Fruit flavor never recovers Above: Cherries with little cherry virus Below: Virus-free Bing cherries Fruit Tree Clean Plant Network; WSU-IAREC, Prosser

12. Questions? Tim Smith WSU Extension Educator 509-667-6540 [email_address] Dr. Ken Eastwell Fruit Tree Clean Plant Network WSU-Prosser IAREC 509-786-9385 [email_address] Fruit Tree Clean Plant Network; WSU-IAREC, Prosser