JSC Latvia's State Forests and JSC Latvijas Finieris agreements No. 55-91-0080-101-14-89 and 2014/20-IP/PA
The main objectives set for this reporting period was the further investigations of birch experimental plantations planted in years 2014 and 2015 and establishment of an inoculation experiment. The inoculation experiment was set up in order to explore the role of five fungus species on development of stem necrosis on birch seedlings – Alternaria alternata, Botrytis cinerea (teleomorph stage: Botryotinia fuckeliana), Fusarium avenaceum (teleomorph stage: Giberella avenacea), Melanconis stilbostoma, Phoma herbarum. The tested species were chosen from frequently observed and potentially dangerous fungal diseases extracted in previous years from damaged birch shoots both in tree nurseries and newly established plantations.
The two-season survival of autumn-planted birch containerized and plug+1 stock is as good as in conventionally spring-planted areas. The autumn-planting of birch can be recommended as everyday practice for extension of the planting period and for optimization of labour utilization. Comparing to areas prepared with disc trencher, the birch planting on mounds made by excavator can increase the seedling survival on heavy soils with high water table and poor infiltration ability but have no effect on birch growth on light, well-drained soils.
On the base of our investigations, the target height for production of birch plug+1 seedlings is set to about 60 cm with the root collar diameter 7–8 mm to reach the optimal root to shoot ratio. The planting of bigger seedlings is associated with low productivity of planting work and often with inappropriate planting quality due to big root plug.
The first evaluation of inoculation experiment shows that tested fungal diseases are weak pathogens and can be hazardous in case if the seedlings have been exposed to some kind of after-planting stress – drought, heavy weed competition and excessive reduction of root system before the planting. The avoidance of mechanical injuries to the birch seedlings during the management in nursery, transportation and planting is crucial to eliminate the infections that can later cause the stem lesions and dieback of shoots.
