A mildew infection has already occurred
This spring, the weather was favorable for a downy mildew infection, with the first oily spots appearing on the leaves of the grapevine. At the moment it cannot be seen everywhere, but due to the heavy rains, the disease process could have started anywhere, which must be blocked with the use of sorbents.
All stages of grape mildew infection depend on the presence of liquid water, that is, the fungus needs water for the germination of winter spores, macrosporangium development and grape leaf development, as well as the formation of infectious spores.
We might think that because of last year’s drought, there are no infectious substances on local farms, but unfortunately that is not the case.
In the summer it was possible to quickly stop using the fungicide, but in the fall it rained, and downy mildew affected the axillary buds in many parts of the country. The winter spores formed did not suffer any damage during the winter, and the temperature and humidity were favorable for them.
In the prediction system of BASF, it was indicated that oil spots appeared on leaves from the southern and northern sides of Lake Balaton, which means that the typical incubation period for this time of about 2 weeks has already passed since the first infection. Symptoms appeared en masse in cisgizard, and secondary infection occurred, Up to a few hours of leaf moisture is sufficient. The grapes are now developing rapidly under the influence of heat, their most receptive state of growth, and are expected to bloom in the first third of June. Damage from the current infection is likely to show.
Weather stations indicated the first risk of infection by mid-May, which it certainly did, even if symptoms did not appear everywhere.
There may have been an infection even before the indication, which is evidenced by the spread of downy mildew. It appears very early this year, which could lead to a serious epidemic if there is still enough rain for the fungus. About a month of complete desiccation can stop the spread of the disease.
Now it is not enough to use contact fungicides, absorbable preparations are needed to stop downy mildew (Enervin, Profiler). To prevent the development of resistance, always use a contact agent in addition to a resorbable fungicide!
Preparations containing the active ingredient potassium phosphonate are also suitable for the prevention and treatment of post-infections, but they must be used as a block, three or four times in a row, until the active ingredient nourishes the plant tissues. Examples of such agents are AktyShield and Delan Pro, but they are not freely available, but “Green Book” preparations.