Articles
Anthracnose disease of walnut in California and its management
Article number
1420_45
Pages
353 – 359
Language
English
Abstract
Walnut (Juglans regia) is a major nut crop in California, USA, with approximately 165,000 ha planted.
Among the few fungal diseases affecting walnut in California, anthracnose, caused by Marssonina juglandis, shows only in certain regions and only when there is rain in the spring.
The same pathogen also infects black walnut (Juglans nigra) in Sacramento Valley.
Although the disease was found sporadically in various counties, San Benito Co. has shown endemic levels of the disease with lesion symptoms on both leaves and fruit in rainy springs.
The pathogen overwinters as perithecia formed in dropped leaves on the ground which release ascospores in early spring (April) as the young leaves and fruit start developing.
Although sanitation by removing leaves from the ground is not economically feasible, the disease can be successfully controlled with timely fungicides, starting early in the spring.
The first application is applied when the emerging leaves are half size of the final size of the leaves.
The second and third applications are applied at about 2-3 weeks after the previous application.
Initially fungicides tried were Bordeaux mixture, liquid lime sulfur, Quilt Xcel, Inspire Super, tebuconazole, Topsin-M, Pristine and Syllit.
The most effective fungicides were Luna Experience, Pristine, and Syllit.
The fungicides Bordeaux mixture and liquid lime sulfur showed no efficacy.
More efficacy fungicide trials were tested in subsequent years and will be discussed in detail.
Among the few fungal diseases affecting walnut in California, anthracnose, caused by Marssonina juglandis, shows only in certain regions and only when there is rain in the spring.
The same pathogen also infects black walnut (Juglans nigra) in Sacramento Valley.
Although the disease was found sporadically in various counties, San Benito Co. has shown endemic levels of the disease with lesion symptoms on both leaves and fruit in rainy springs.
The pathogen overwinters as perithecia formed in dropped leaves on the ground which release ascospores in early spring (April) as the young leaves and fruit start developing.
Although sanitation by removing leaves from the ground is not economically feasible, the disease can be successfully controlled with timely fungicides, starting early in the spring.
The first application is applied when the emerging leaves are half size of the final size of the leaves.
The second and third applications are applied at about 2-3 weeks after the previous application.
Initially fungicides tried were Bordeaux mixture, liquid lime sulfur, Quilt Xcel, Inspire Super, tebuconazole, Topsin-M, Pristine and Syllit.
The most effective fungicides were Luna Experience, Pristine, and Syllit.
The fungicides Bordeaux mixture and liquid lime sulfur showed no efficacy.
More efficacy fungicide trials were tested in subsequent years and will be discussed in detail.
Publication
Authors
T.J. Michailides, V. Gabri, D.P. Morgan
Keywords
walnut, anthrachnose, Marsosonia juglandis, sanitation, fungicide
Groups involved
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