Cellulose fibres are biodegradable. Their biodeterioration results in a reduction of the degree of polymerization and thus textile strength loss. The risk of a microbiogenous decay of such textiles is linked to humidity and therefore to the corrisponding range of application. Cellulosic clothing and furnishings may suffer from humid storage conditions. Awnings, covers and tarpaulins need protection by technical antimicrobials, when moisture is present. Biodegradable geotextiles can be use for plantations on steep slopes against erosion. Microbiological tests can be divided into in-use-conditions, close to the practice tests (e.g. Soil burial test, saturated atmosphere test) and in-vitro test (tests on agar). Some results of soil burial tests, fungus resistance tests and bacterial resistance tests are presented. Tables, references.