Articles
Epidemiology and management of Botryosphaeria canker and blight of walnut in California
Article number
1420_43
Pages
337 – 344
Language
English
Abstract
The first report of a Botryosphaeria canker in California walnuts was a disease named “melaxuma” on ‘Franquette’ walnuts in the 1915. No additional studies were done on this disease until 2014 when growers reported noticeable reductions in yields.
Botryosphaeria canker and blight is caused by 10 Botryosphaeriaceae species among which Neoscytalidium dimitiatum that was reported in 1956 causing branch wilt of walnut under the old name Hendersonula toruloidea. Infections occur in the spring when rainy weather spreads the pycnidiospores to the susceptible tissues.
Immature fruit, leaf and peduncle scars as well as pruning wounds can be infected while not any disease symptoms and/or signs of the disease can occur on leaves.
Infections on fruit remain latent until late in August when symptoms such as blighting of fruit hulls appears.
Infection from one fruit can move to the neighboring fruit and through the peduncle move into the sustaining spur (parental shoot). As the canker progresses into the spur, it kills both male and female buds, representing the following year’s crop.
Both the blighted fruit and the killing of fruiting buds may partially explain the reduction of walnut yields in California.
Fungicides that control Botryosphaeria panicle and shoot blight of pistachio were tested and were very effective in controlling the Botryosphaeria disease of walnut.
A fungicide efficacy trial will be presented here as an example.
Botryosphaeria canker and blight is caused by 10 Botryosphaeriaceae species among which Neoscytalidium dimitiatum that was reported in 1956 causing branch wilt of walnut under the old name Hendersonula toruloidea. Infections occur in the spring when rainy weather spreads the pycnidiospores to the susceptible tissues.
Immature fruit, leaf and peduncle scars as well as pruning wounds can be infected while not any disease symptoms and/or signs of the disease can occur on leaves.
Infections on fruit remain latent until late in August when symptoms such as blighting of fruit hulls appears.
Infection from one fruit can move to the neighboring fruit and through the peduncle move into the sustaining spur (parental shoot). As the canker progresses into the spur, it kills both male and female buds, representing the following year’s crop.
Both the blighted fruit and the killing of fruiting buds may partially explain the reduction of walnut yields in California.
Fungicides that control Botryosphaeria panicle and shoot blight of pistachio were tested and were very effective in controlling the Botryosphaeria disease of walnut.
A fungicide efficacy trial will be presented here as an example.
Publication
Authors
T.J. Michailides, Shui-Fei Chen, D.P. Morgan, V. Gabri, G. Fiore
Keywords
Botryosphaeria canker and shoot blight, epidemiology, Juglans regia, latent infection, disease management
Groups involved
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