First Time In Finland Research Articles

Occurrence and pathogenicity of Yersinia ruckeri at fish farms in northern and central Finland

Abstract. Salmonid fish at fish farms in northern and central Finland and perch, Perca fluviatilis L., roach, Rutilus rutilus (L.), and whitefish, Coregonus sp., from four lakes in central Finland were studied between 1985 and 1990 for the occurrence of Yersinia ruckeri. The bacteria were found in fish from both areas, but in most cases, only single diseased salmon, Salmo salar L., brown trout, S. trutta L., rainbow trout, Oncorhynchus mykiss (Walbaum), whitefish and perch were encountered and were always connected with stress conditions. One clinical outbreak occured in salmon fingerlings in northern Finland, and the fish were successfully treated with trimethoprim‐sulpha. Monthly monitoring of lake fish revealed two symptomless carrier perch in two lakes. Outwith the main study a moribund perch with yersiniosis was found in a polluted lake, and for the first time in Finland, a rainbow trout was also found to have contracted yersiniosis in a small private pond. Sorbitol‐positive and negative isolates have been found to occur in both moribund and carrier farmed fish, indicating that the sorbitol test is not essential when evaluating the pathogenicity of Y. ruckeri.

The appearance of soil-borne viruses in Finnish plant nurseries II

In the beginning of the 1970’s, the occurrence of soil-borne viruses in 30 Finnish nurseries and experimental fields of garden plants at 3 research stations was mapped. Viruses were isolated on 26.9 % of the 672 plant and soil samples collected. The two most commonly found viruses were tobacco necrosis virus (TNV), 42.5 %, and tobacco rattle virus (TRV), 23.7 %. Tomato black ring virus (TBRV) and raspberry ringspot virus (RRSV) were isolated for the first time in Finland. The abundant occurence of TBRV in 32 samples was due to the abundance of Phlox paniculata samples. RRSV was isolated from only a few samples. The vectors of all of the above-mentioned viruses were found in many samples. The fungus vector of TNV, Olpidium brassicae, was investigated by examining the roots microscopically. The vector of TRV, the Trichodorus sp. nematodes, and the vector of TBRV and RRSV, the Longidorus sp. nematodes, were isolated from soil samples. In addition to the foregoing, tobacco mosaic virus was isolated from 31 samples of 6 nurseries and 2 experimental fields. Viruses were isolated from many weed samples, especially from roots of Senecio vulgaris and Stellaria media. Perennials proved to be virotic. All of the above mentioned viruses, especially TBRV and TRV, were isolated from Phlox paniculata; TBRV was also found in an Astilbe x arendsii sample. Dicentra spectabilis, like Phlox, was commonly infected with TRV. No clear results could be obtained from control experiments.

The appearance of soil-borne viruses in Finnish plant nurseries

In studies conducted by the Department of Plant Pathology of the Agricultural Research Centre, soil-borne viruses were found in soil samples from seven nurseries out of thirteen sampled and from fields at two experimental stations in south and south-west Finland. Tobacco necrosis virus was identified for the first time in Finland in 12 isolates and in addition tobacco rattle virus in 8 isolates. All these isolates were made from 193 soil and plant samples collected in late autumn of 1970. For the first time in Finland the nematode Trichodorus pachydermus Seinhorst was identified from extracts of TRV-infected soil and plant samples.

The resistance of some potato varieties to spraing caused by tobacco rattle virus

TRV was detected and identified for the first time in Finland. According to the information available rattle is an uncommon potato disease in our country. Spraing symptoms were detected in tubers grown in a trial field at Tikkurila in 1968, and during the following years it was possible to make observations on the resistance of 10 varieties to the disease. Sieglinde and Pito were most susceptible followed by Jaakko, Eigenheimer, Olympia and Valtti. Amyla, Record and Realta were fairly resistant and Bintje most resistant.