Little Cherry Virus

Little Cherry Virus Disease

Little cherry disease is a serious disease of sweet and sour cherry in British Columbia, caused by the Little Cherry Virus (LChV). The disease occurs in areas of the Okanagan and Kootenay valleys, and has been under an official control program for many years.

Symptoms:

Little Cherry Disease primarily affects fruit size and quality. Fruit on infected trees are smaller than normal, poorly coloured, and lacking in flavour. Fruit symptoms are not always uniform, and may appear on only part of the tree. Severity of fruit symptoms varies by variety, although none are immune. Infected trees may be slightly less vigorous, but generally there is no noticable deterioration in the overall health of the tree. A premature leaf reddening occurs in the fall on infected trees of some varieties, including Sam and Lapins.

LChV-infected lapins LChV-infected celeste

LChV-infected Lapins fruit (left); healthy fruit (right) LChV-infected Celeste fruit (left); healthy fruit (right)

LChV-infected Sweethearts Healthy Sweetheart cherries

Smaller, paler fruit on Little Cherry Virus-infected Sweetheart Cherry Healthy Sweetheart cherry fruit

healthy Lapins

LChV-infected Lapins fruit Healthy Lapins fruit

Life Cycle

Little Cherry Disease is spread from tree to tree by the apple mealybug. This pest is usually present at very low levels in commercial cherry orchards and can be difficult to find. It does not fly, but spreads to adjacent trees where branches are close together. The crawler stage of the insect may also be wind-blown for short distances.

Little Cherry Disease can also be spread by propagation of infected stock, including rootstocks and budwood. Most long-distance spread has been by propagation and distribution of infected trees. Ornamental flowering cherries are symptomless carriers of the virus, and can also act as sources of the disease.

Control and Prevention

There is no cure or treatment for little cherry disease. Trees suspected of being infected should be removed. Little Cherry disease is a declared pest under the provincial Plant Protection Act. The Little Cherry Regulation allows for destruction of infected trees, and also prohibits the growth or sale of ornamental flowering cherries in the Okanagan and Creston Valleys.

In areas with little cherry virus, orchardists should be diligent to control the apple mealybug. High mealybug populations can lead to rapid spread of the disease. In orchards with good insect control programs, generally the progression of the disease is very slow.

Be sure new planting stock is certified as virus-tested and from a reliable source.

When replanting cherry blocks it is important to remove all of the old cherry trees from a block before planting new cherry trees. This will help to break the cycle of LChV infection, and is particularly important in areas with known LChV problems. If possible, locate new plantings at some distance (eg. over 10 meters) from older, established cherry orchards to slow the spread of LChV into the new blocks. Isolating new plantings will also reduce the spread of other harmful viruses, which are not uncommon in older cherry trees.

Further Information:

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