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Symptoms can be highly variable and depend on the virus strain and the host species/cultivar infected.
In sensitive Malus cultivars, symptoms can include chlorotic leaf spots and/or ring and line patterns on foliage, asymmetric leaf distortion, premature leaf drop, stunting, terminal dieback, inner bark necrosis and xylem pitting, and local bark necrosis surrounding the inoculum buds (Mink, 1989).
In plum, the virus can cause bark splitting and mild pox symptoms sometimes mistaken for plum pox. Symptoms include brownish-red areas on the bark followed by severe cracking and splitting. Necrosis may proceed to the cambium and can lead to branch die back. The development of the tree is slowed and a vigorous growth of suckers around the tree base occurs (Németh, 1986).
While plum pseudopox, caused by ACLSV infection, decreases the market value of fruit from infected trees, the losses do not compare to those attributable to plum pox virus (Németh, 1986). Symptoms of the disease are usually restricted to sunken spots, bands or rings on the skin of fruit, although in individual trees, leaf symptoms may also occur (Németh, 1986). Fruit symptoms of pseudopox are difficult to distinguish from those of plum pox, but leaf symptoms are more distinct.
The disease known as 'apple ringspot' is believed to be caused by dual infections with ACLSV and a severe strain of Apple stem pitting virus. More details can be found in a separate datasheet on this disease.
Most varieties of sweet cherry and sour cherry are latently infected by ACLSV, although in some cultivars the appearance of necrotic, sunken spots on the fruits has been associated with dual infection by ACLSV and Prunus necrotic ringspot virus (Németh, 1986).
As with other susceptible fruit trees, in peach the virus often causes graft-incompatibility, leading to necrosis and early decline. It can also cause dark-green, sunken spots or wavy lines on peach leaves (Németh, 1986).
In apricot, the virus can cause rosetting as well as fruit symptoms resembling apricot ring pox. The sensitivity of some apricot seedling rootstocks to the virus may also cause graft-incompatibility (Németh, 1986; Hansen, 1995).
The virus can easily be controlled through the use of virus-free (indexed) propagation material (Németh, 1986). When virus-free planting materials are used to initiate a new planting, the stock remains virus-free (Hansen, 1995).
Cultural Control and Sanitary Measures
ACLSV is readily eliminated from apple by thermotherapy (Németh, 1986). Heat treatment of prune trees with bark split symptoms can also lead to elimination of ACLSV and regeneration of some healthy buds (Dunez et al., 1972).
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
Although ACLSV can lead to a wide range of symptoms on various Malus cultivars, many of the commercial apple cultivars are symptomless hosts if grown on seedling rootstocks or on non-sensitive clonal rootstocks (e.g., East Malling, Malling Merton; Smith et al., 1988; Mink, 1989).
However, in Japan, where ACLSV-sensitive rootstocks (e.g., Malus prunifolia var. ringo) are commonly used, trees decline in vigour and can become unproductive within 3 years after top-working with ACLSV-infected cultivars (Németh, 1986; Mink, 1989; Yanase et al., 1990).
In pear, the virus causes pear ring pattern mosaic, essentially affecting the development of young trees, slowing the growth of sensitive varieties by 25-60% and increasing sensitivity to frost (Németh, 1986).
Infection of plum by the strain of ACLSV causing plum bark split severely damages the tree, making maintenance uneconomical (Németh, 1986).