Plum Pox Virus (PPV)
Beginner
This pest affects:
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Scientific Name
Plum Pox Virus (PPV
Identification
Symptom expression is variable and depends on the host, the cultivar, the strain of PPV, the age of the infected tree, and the environment. Symptoms may be observed on only a few leaves or fruit, along one limb, or they may be expressed throughout the entire tree. In some years symptoms may appear in spring and early summer, but fade or disappear during periods of hot weather only to return again when temperatures moderate.
Infected trees rarely die but frequently become less productive as the disease progresses. A measurable decrease in growth has been observed on severely infected trees. Sensitive plum varieties may have bark splitting. Peach and nectarine varieties with showy flowers may display colour breaking on petals.
Leaves
- Light chlorotic or yellow rings, spots, and blotches
- Yellow line patterns along veins, vein clearing, and leaf distortion
- On some cultivars, spots may appear as dead or necrotic tissue, while other cultivars do not express obvious symptoms
Flowers and Fruit
Peach and nectarine
- With some varieties such as Veecling colour breaking symptoms may be evident on blossom petals, exhibiting colour varigation and line patterning
- Faint mottled yellow lines, patches and rings on green fruit
- As the fruit matures and ripens the lines, patches and rings remain yellow, surrounded by the normal blush colour
- Because of the uneven distribution of the virus within the tree, different fruit on the same infected tree may appear symptom-less while other fruit appear severely diseased
- Sugar content may also be reduced in some varieties
- Fruit of some varieties may drop prematurely
- Infected peach fruit ripens a few days earlier with sugar levels being slightly higher
Plum
- Chlorotic lines, dark sunken rings and spots
- Pocked and severely deformed
- Premature fruit drop
- Sugar content is significantly reduced in infected fruit, which becomes pulpy, tasteless and unmarketable
Apricot
- Chlorotic lines, dark sunken rings and spots
- Pocked and severely deformed
- Rings and spots occasionally observed on the pits of infected fruit without external symptoms
- Sugar content is significantly reduced in infected fruit, which becomes pulpy, tasteless and unmarketable
Often Confused With
Peach latent mosaic viroid: fruit are irregularly shaped, flattened, and colorless with cracked sutures and enlarged pits.
Period of Activity
The virus is at its highest concentration in leaves mid-spring through early summer, before temperatures exceed 30ºC. Aphid vectors are usually present between early June and mid-July.
Scouting Notes
Stone fruit trees appear to be most susceptible from mid spring to early summer when migratory aphid vectors are moving through orchards. Older leaves on trees become more resistant to infection by aphid vectors as the season progress. The virus is located in the basal 1/3 of growth of non-elongated spur. Scout susceptible orchards at least twice per season and concentrate on looking for symptoms in the basal leaves of new season growth.
Symptoms often do not appear in infected trees until 2-3 years after infection. By the time symptoms are observed the virus has spread to other trees within the orchard or region. Inspecting trees for symptoms is not a reliable method for detecting all infection within the orchard due to the latency of symptom development and the fact that symptoms may not be less apparent on all varieties.
Threshold
There is no threshold established for PPV. However, as it can be spread rapidly from infected to non-infected trees by aphid vectors, any positive trees should be removed as quickly as possible.
Advanced
This pest affects:
|
|
|
Scientific Name
Plum Pox Virus (PPV
Identification
Symptom expression is variable and depends on the host, the cultivar, the strain of PPV, the age of the infected tree, and the environment. Symptoms may be observed on only a few leaves or fruit, along one limb, or they may be expressed throughout the entire tree. In some years symptoms may appear in spring and early summer, but fade or disappear during periods of hot weather only to return again when temperatures moderate.
Infected trees rarely die but frequently become less productive as the disease progresses. A measurable decrease in growth has been observed on severely infected trees. Sensitive plum varieties may have bark splitting. Peach and nectarine varieties with showy flowers may display colour breaking on petals.
Leaves
- Light chlorotic or yellow rings, spots, and blotches
- Yellow line patterns along veins, vein clearing, and leaf distortion
- On some cultivars, spots may appear as dead or necrotic tissue, while other cultivars do not express obvious symptoms
Flowers and Fruit
Peach and nectarine
- With some varieties such as Veecling colour breaking symptoms may be evident on blossom petals, exhibiting colour varigation and line patterning
- Faint mottled yellow lines, patches and rings on green fruit
- As the fruit matures and ripens the lines, patches and rings remain yellow, surrounded by the normal blush colour
- Because of the uneven distribution of the virus within the tree, different fruit on the same infected tree may appear symptom-less while other fruit appear severely diseased
- Sugar content may also be reduced in some varieties
- Fruit of some varieties may drop prematurely
- Infected peach fruit ripens a few days earlier with sugar levels being slightly higher
Plum
- Chlorotic lines, dark sunken rings and spots
- Pocked and severely deformed
- Premature fruit drop
- Sugar content is significantly reduced in infected fruit, which becomes pulpy, tasteless and unmarketable
Apricot
- Chlorotic lines, dark sunken rings and spots
- Pocked and severely deformed
- Rings and spots occasionally observed on the pits of infected fruit without external symptoms
- Sugar content is significantly reduced in infected fruit, which becomes pulpy, tasteless and unmarketable
Often Confused With
Peach latent mosaic viroid: fruit are irregularly shaped, flattened, and colorless with cracked sutures and enlarged pits.
Biology
There are multiple strains of the virus. The D-strain is the only strain currently present in North America and its host range includes apricot, plum, peach and nectarine as well as several Prunus species including wild plum (P. americana), cherry plum (P. cerasifera), dwarf flowering almond (P. glandulosa), and black thorn (P. spinosa).
The virus spreads between regions through the movement of infected propagating material. The plum pox virus can also spread from infected trees to healthy trees through root grafts but root grafts appear to be a minor method of spread. There is no evidence that the virus can be spread on pruning shears or knives. Once Plum pox becomes established within an orchard the virus spreads from tree to tree by several species of virus-carrying winged migrating aphids.
Aphids can acquire plum pox virus within a few seconds after sampling an infected plant. If they are winged migratory aphids and have found the plant unacceptable for feeding, they may move quickly from the infected plant onto a healthy plant, transmitting the virus in the process. Aphids usually retain the PPV no more than an hour, but retention for up to 1–3 days has been reported. Aphids rapidly lose the virus particles after the next test probe or feeding and must again sample an infected plant to continue to transmit the virus. If the next plant the aphid feeds on is not a PPV host plant, then the virus is destroyed and the aphid is unable to transmit it to additional plants. A single aphid, therefore, cannot transmit the virus to more than one plant following acquisition of the virus.
Transient, non-colonizing, winged aphid species that sample many plants in search of appropriate hosts favour the transmission of plum pox virus. Non-winged colonizing aphids are probably not mobile enough to contribute substantially to the spread.
Period of Activity
The virus is at its highest concentration in leaves mid-spring through early summer, before temperatures exceed 30ºC. Aphid vectors are usually present between early June and mid-July.
Scouting Notes
Stone fruit trees appear to be most susceptible from mid spring to early summer when migratory aphid vectors are moving through orchards. Older leaves on trees become more resistant to infection by aphid vectors as the season progress. The virus is located in the basal 1/3 of growth of non-elongated spur. Scout susceptible orchards at least twice per season and concentrate on looking for symptoms in the basal leaves of new season growth.
Symptoms often do not appear in infected trees until 2-3 years after infection. By the time symptoms are observed the virus has spread to other trees within the orchard or region. Inspecting trees for symptoms is not a reliable method for detecting all infection within the orchard due to the latency of symptom development and the fact that symptoms may not be less apparent on all varieties.
Threshold
There is no threshold established for PPV. However, as it can be spread rapidly from infected to non-infected trees by aphid vectors, any positive trees should be removed as quickly as possible.
Management Notes
Remove infected trees as they are a reservoir of the virus.
Do not import plant material from other areas of the world. Plant only virus-free, certified nursery stock. Do not plant trees that were not propagated with budwood from virus tested, virus free mother trees.
No resistant varieties are currently commercially available in Canada.
There are no anti-virus treatments that can be applied to infected trees. Intensive knock-down insecticide programs controlling aphid vectors have not stopped the spread of PPV in Europe. Insecticides cannot kill immigrating aphids quickly enough to prevent acquisition and transmission, and thus regular sprays do not reduce the spread of PPV.
Oil sprays have demonstrated the reduction in virus transmission and new anti-feeding insecticides may reduce transmission rate.
Some information included above excerpted from;
