Testing the effectiveness of microbial biostimulants to increase the resistance of the variety Chardonnay to “Bois noir” phytoplasma

Microbial strain: Bacillus licheniformis (min. 1×10⁷ cfu/ml) - max. 5%.

pH value: 6.5 – 7.5

UV-resistant, good tolerance to low and high temperatures, no risk of resistance, zero safety period.

Microbial strain: Bacillus thuringiensis spp. kurstaki, Bacillus thuringiensis spp tenebrionis (1×10⁹ cfu/ml), Photorhabdus luminescens (1×10⁹ cfu/ml)

pH value: 6.5 – 7.5

UV-resistant, good tolerance to low and high temperatures, no risk of resistance, zero safety period.

Microbial strain: genus Thiobacillus.

pH value: 7–8

Leaves are discoloured, edges roll downward, leaf blade becomes brittle.

Leaf rolling often results in an angular shape.

Spots form on sun-exposed surfaces of the leaves, which enlarge into bands along the veins. These will gradually cover the entire leaf surface.

Colour of the spots and bands varies with the cultivar: white-fruited varieties usually have creamy-yellow spots and red-fruited cultivars have reddish spots.

Flowers dry out and fruit will not set on initially infected plants.

Bunches on plants that become infected later in the season will become brown and shrivelled.

Fruit will drop very easily with some varieties.

Canes ripen poorly and unevenly, often showing green and brown sections along the cane.

Canes with poorly ripened wood will appear rubbery, often causing a “weeping” appearance.