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POSTERS: Cultural control

Aerated steam by the ‘Plant Sauna’ eradicates powdery mildew from strawberry transplants
Arne Stensvand - Norwegian Institute of Bioeconomy Research. Claudio Dias Da Silva Jr.- Escola Superior de Agricultura (Esalq), Universidade de Sao Paulo (USP), Nan-Yi Wang- Gulf Coast Research and Education Center, University of Florida, Chloe Grieu- Norwegian Institute of Bioeconomy Research (NIBIO), Belachew Asa

The ‘Plant Sauna’ is a closed container with an even distribution of aerated steam at a set temperature. It was originally developed in Norway to disinfest greenhouse equipment but is now being adapted to treat strawberry (Fragaria × ananassa) planting material for diseases and pests. Aerated steam from the ‘Plant Sauna’ has successfully been used to eliminate or significantly reduce important diseases in transplants of strawberry. Powdery mildew (Podosphaera aphanis) on strawberry transplants may rapidly reach epidemic levels after planting, and such plants may carry fungicide resistant strains from nurseries. The standard steam treatment of strawberry planting material developed in Florida is a 1-hour pre-treatment at 37°C to increase heat tolerance of the plants, followed by 1 hour at ambient temperature (20-25°C), and then 4 hours at 44°C. In repeated experiments with strawberry plug plants infected with powdery mildew, the disease was completely eradicated. Two hours at 44°C was also sufficient to kill the pathogen. Following the treatments, plants were kept for 21 days under conditions conducive for powdery mildew. There was no regrowth of the pathogen on leaves infested prior to the treatments, and no disease appeared on newly developed foliage. No negative effects on yields following steam treatments have so far been observed. Experiments are continued to pinpoint doses (temperature × time) necessary to manage powdery mildew on strawberry transplants.