- IFP & Organics
- Change Log
Causal Agent: We now know that there are at least two viruses causing Little Cherry Disease in British Columbia. Little cherry virus 2 was first detected in British Columbia in the Kootenays in the 1930’s and in the Okanagan in 1969. Little cherry virus 1 was first detected in BC in 1999, but has probably been present for much longer.
Symptoms: Symptoms can be quite variable depending on the variety and strain of the virus present. Little cherry virus 2 symptoms include small fruits which do not ripen fully and have a flat taste. The fruits are half to two-thirds normal size, dull red, and on some varieties may be pointed with flat sides (Fig. 1). Fruit symptoms are most pronounced in the Lambert variety.
Figure 1. Comparison of fruit from a little cherry disease-infected tree (top) to fruit from a clean tree. (BCMA)
Foliage symptoms occur in several varieties including Sam and Lapins with early leaf reddening occurring in late August or September (Fig. 2), but this is not a reliable indicator on mature orchard trees because other factors can cause red leaves. Symptoms of little cherry virus 1 appear to be less severe than for Little Cherry Virus 2 in BC orchards, but this is not well documented.
Figure 2. Leaf symptoms of little cherry disease. (BCMA)
Little cherry virus 2 is spread by the apple mealybug. The virus is also readily transmitted by propagation. It is not transmitted by pollen, seed, soil or by pruning tools. Little cherry virus 1 can also be spread by propagation. The insect vector is not known.
Little cherry virus 2 is present primarily in the Penticton and Creston areas. A few positive trees have also been detected in Summerland and Kelowna in recent years. Little cherry virus 1 appears to be more widely distributed, with positive trees detected from all areas of the Okanagan/Similkameen and Creston valleys.
Avoid planting infected stocks or using budwood from trees that have not been tested for freedom from viruses.
Remove all trees known or suspected to be infected with little cherry disease to limit spread within your orchard. Carefully inspect fruit quality on trees in high risk areas for small fruit symptoms.
Advise the BCMAL Plant Pathologist (Kelowna) of any trees suspected of having little cherry virus. Trees with little cherry virus must be removed under the authority of the B.C. Plant Protection Act, Little Cherry Control Regulation.
Do not interplant cherry trees amongst older cherry trees that may be carrying the virus (symptoms are not always obvious). It is best to remove whole blocks of older cherry trees before replanting to cherry, particularly in orchards or districts with a history of little cherry virus. Note: this will also help to delay introduction of other cherry virus diseases and cankers.
Control apple mealybug. All cherry growers with orchards where little cherry virus 2 has been found should apply recommended sprays, as indicated in the section on mealy bugs, page xx. Growers in areas with a high incidence of little cherry (Penticton, Creston) should also follow the program to protect their trees.
Japanese flowering cherries are symptomless carriers of the little cherry virus. For this reason, it is illegal to grow these ornamental cherries in the Okanagan, Similkameen or Creston Valleys.