ISHS Acta Horticulturae 129: III International Symposium on Small Fruit Virus Diseases
EPIDEMIOLOGY OF VIRUS INFECTIONS IN CENTRAL CALIFORNIA STRAWBERRY FRUITINGS FIELDS |
| Authors: | A. Pisi, A.H. Gold, B. Rogers |
| Abstract:
During the past five years we have studied the commercial strawberry fruiting fields of Central California to determine the kinds of viruses infecting plants in the fields. We also investigated spacial and seasonal patterns of infectioon spread, as well as year to year patterns and sources of virus inoculum. During our surveys we detected only infection by Mild Yellow Edge (MYE), Mootle (M), Crinkle (C), and Tobacco Strike virus (Strawberry Necrotic Shock (TSV)). The same kinds of viruses were detected inall commercial fields except for TSV which was fooound only in the Pajaro variety . In the past year we also detected these viruses in plants comming from two different nursery sources sampledd and indexed before and after planting in the fruiting field. Detection of the above mentioned viruses was accomplished by observing symptoms on plants of indicator strawberry varieties, which were leaf-grafted, each with two leaves taken from individual fruiting field or nursery plants. For our studies in 1981–82, three different plots were chosen in two different ranches planted with the variety Pajaro (C45). Both ranches were located in the Watsonville area; the first on a slope exposed directly to the prevailing ocean winds, the second more inland and more protected by the ocean winds. The three plots chosen (Plots A,C,D) were repeatedly sampled, and each plant in the plot was indexed. Plot A, selected in the field located toward the ocean, consisted of two beds, each one with two rows, each row containing 100 plants. Thus the plot consisted of 400 plants. It was planted in August 1980, sampled and indexed in March, May and August 1981, subsequently in February 1982. The other two plots (Plot C and D), located in a ranch more inland were not adjacent in the field and had plants coming from two different nursery sources. They were planted in August 1980. They consisted of one bed each, with two rows, each row of 100plants. Thus each plot contained 200 plants. They were sampled and indexed in June 1981. We also had the opportunity in 1981 to sample 200 plants from each of two nurseries before they were planted in the field. These nursery plants were randomly removed from boxes which were held in cold storage fo about 9 months. They were poptted in the greenhouse, kept insect-free, were indexxed individually by leaf-grafting, and then transplanted as a plot (Plot e) in the fruiting field. Thus we were able to determine the level of infection of the nursery stock and subsequent pattern of spread from known infected nursery plants. In the plot A, selected in the ranch near the ocean, the virus infection increased considerably from March to May, but it remained almost stable during August 1981 and February 1982. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
