Organic PLUS Deliverable 3.4: Lab and field trial evaluation - NORSØK

Summary in the original language of the document

This study tested the efficiency of ozonised water against late blight disease in potatoes. Seed potatoes were infected with late blight and treated with ozonised water. The effect of spraying ozonised water on potato leaves infected with late blight was assessed. A slurry with late blight pathogens was sprayed onto the seed potatoes prior to the planting. Two days later, but before planting, seed potatoes were treated with ozonised water, either for 10 seconds or 3 minutes. At the onset of germination, the leaves were sprayed once a week during the whole growing season with tap water or ozonised tap water. The experimental design was a Split Plot Design with 6 blocks inside 2 main blocks (tap water spray or ozone water spray), each split into 4 experimental plots (1.-4. pre-treatments). The following recordings were done during the growing season:
• Germination level
• Canopy height
• Late blight assessments (twice)
• Yields
The germination level for the different pre-seeding treatments were about the same. This indicates that ozonised water did not affect the germination of the potatoes. The effect on canopy height of spraying leaves with ozonised water was generally small. However, for two of the four pre-treatment groups, the canopy height was somewhat larger for plants sprayed with ozonised water.
In the first late blight assessment, potato leaves sprayed with ozonised water had about 7 % less infection than those sprayed with tap water. This indicates that spraying ozonized water may supress development of late blight on potatoes leaves.
For the yields, small differences between treatments were found. The highest yields were found for potatoes treated with ozonised water for 3 min before seeding and regularly sprayed with ozonised water during the summer.
Although there are some indications that treating seed potatoes and potato foliage with ozonised water may supress late blight disease, the efficiency of this treatment on heavily infected potatoes is not strong enough to be recommended. It may be a useful method to protect potatoes from airborne pathogens of late blight, but that topic was not tested in this study.