A total amount of 90 pig tonsil samples were investigated to detect presence of Y.enterocolitica 4/O:3. Samples were collected in two large-scale Latvian slaughterhouses from five pig herds during February and March, 2006. Samples were investigated with direct plating onto selective CIN agar plates according to ISO 10273 method, with subsequent cold enrichment for 2 weeks at 4 deg C in accordance with NMKL 117 method. Y.enterocolitica positive isolates were investigated for pyrazinamidase and lipase activity, indole production and salicine, xylose, trehalose fermentation. Slide agglutination reaction with commercial antisera O:3 was carried out for detection of Y.enterocolitica sevovars. Pathogen was isolated from all five herds with 30% mean prevalence. Incidence of Y.enterocolitica 4/O:3 depending on herd varied from 20 to 45%. High incidence of Y.enterocolitica in pig tonsils indicates that animals are important reservoir of this pathogen in Latvia. Further studies about incidence of Y.enterocolitica pathogenic bioserotypes in pig population and contamination pattern with pathogen in slaughterhouses are needed.

Potato is the second important crop in Latvia. The area covered with potato is about 50 thousand hectares. Potato late blight caused by Phytophthora infestans (Mont.) de Bary is the most serious potato disease. Weather conditions in Latvia are very favourable for the development of potato late blight and it is occuring almost every year. The biology of P.infestans was the subject of a number of authors - plant pathologists. Research results about P.infestans population biology and epidemiology are presented in this review, especially focusing on the changes of pathogen biology.

The leaf spot diseases of bananas and plantains, Sigatoka and Black Sigatoka, caused by Mycosphaerella musicola and M. fijiensis var. difformis are distributed worldwide and only in Central America respectively. Epidemiological studies are described in detail including seventy of the pathogens at different sites and correlation with climatic data. Susceptibilities of different banana and plantain genomic groups were found to be nearly identical for both diseases except that Black Sigatoka is more virulent so that both pathogens occupy the same ecological niche. A method developed to test the susceptibility of musa clones to Black Sigatoka using plantlets derived from shoot tip culture is described