Verticillium wilt
Beginner
This pest affects:
Scientific Name
Verticillium dahliae
Identification
Leaves
- In young trees, yellowing and sudden wilting in late summer. Symptoms sometimes progress from the base of the branch upwards
Branches & Wood
- Dieback on one or more branches, usually on one-year-old wood frequently on one side of the tree
- Brownish discolouration or streaking in the vascular tissue of affected limbs, but this symptom is not always apparent in cherry
- Affected trees become unthrifty and may die, however diseased trees often recover spontaneously
- Recovery is more likely when symptoms are mild
- Wilt usually causes death of 30-50% of branches on an affected tree
Often Confused With
Drought: Symptoms occur uniformly throughout tree rather than localized to one limb or one side of the tree
Phytophthora root rot- reddish discolouration at crown and into roots
Nutrient deficiencies- no vascular discolouration; symptoms do not occur only on one side of tree
Peach X disease- no shothole injury on leaves
Period of Activity
Scouting Notes
Above ground wilt symptoms are evident, usually on one side of the tree, during periods of high water demand. Cut wilted shoots and/or limbs to look for vascular discolouration.
Threshold
There is no threshold established.
Photo sources:
- http://www.ipm.msu.edu/diseases/verticillium_wilt;
- https://pnwhandbooks.org/plantdisease/host-disease/peach-prunus-persica-verticillium-wilt
Advanced
This pest affects:
Scientific Name
Verticillium dahliae
Identification
Leaves
- In young trees, yellowing and sudden wilting in late summer. Symptoms sometimes progress from the base of the branch upwards
Branches & Wood
- Dieback on one or more branches, usually on one-year-old wood frequently on one side of the tree
- Brownish discolouration or streaking in the vascular tissue of affected limbs, but this symptom is not always apparent in cherry
- Affected trees become unthrifty and may die, however diseased trees often recover spontaneously
- Recovery is more likely when symptoms are mild
- Wilt usually causes death of 30-50% of branches on an affected tree
Often Confused With
Drought: Symptoms occur uniformly throughout tree rather than localized to one limb or one side of the tree
Phytophthora root rot- reddish discolouration at crown and into roots
Nutrient deficiencies- no vascular discolouration; symptoms do not occur only on one side of tree
Peach X disease- no shothole injury on leaves
Biology
This disease is caused by a soil-borne fungus which invades the tree roots and grows up into the xylem and plugs it causing symptoms in the upper part of the tree. The symptoms progress until the infected shoots die and dry up later in the season. Once temperatures increase in the summer, the fungus dies out in the upper part of the tree and no more shoots die. Although shoot dieback is rarely observed in stone fruit trees older than five years, it is very likely that tree growth and yield will be affected even in the absence of disease symptoms.
Damage is likely to be serious if stone fruit trees are planted in land previously cropped with susceptible plants such as tomatoes, potatoes, peppers, eggplants, strawberries, melons or squash, or if these crops are interplanted in young stone fruit orchards. The fungus can survive in the soil as microsclerotia as well as in debris of previous susceptible crops for many years. It may also overwinter in tree roots.
Verticillium wilt is more common in young orchards, but older trees may also be affected. High populations of pathogenic nematodes in the soil can increase the amount of damage.
Period of Activity
Scouting Notes
Above ground wilt symptoms are evident, usually on one side of the tree, during periods of high water demand. Cut wilted shoots and/or limbs to look for vascular discolouration.
Threshold
There is no threshold established.
Management Notes
Avoid planting sites known to be infested with Verticillium.
Do not intercrop with other susceptible species such as tomatoes, potatoes, peppers, eggplants, strawberries, melons or squash,
Prune out dead wood.
Reduce nitrogen application to produce only 30 cm of terminal growth.
Do not overwater - the disease is more severe in wet soil.
Chemical Control
There are no chemical treatments for trees infected with Verticillium wilt.
Pre-plant soil fumigation will help to reduce the amount of Verticillium in the soil in known-infested sites. Refer to the article on replant disease for more information on fumigation.
Some information included above excerpted from;
- http://www.ipm.ucdavis.edu/PMG/r602101511.html
- http://pubs.aic.ca/doi/pdfplus/10.4141/cjps73-121
- http://cestanislaus.ucdavis.edu/files/111475.pdf
- Integrated Pest Management for Stone Fruits. LL Strand ed.
Photo sources:
- http://www.ipm.msu.edu/diseases/verticillium_wilt;
- https://pnwhandbooks.org/plantdisease/host-disease/peach-prunus-persica-verticillium-wilt