If grapes are covered with a white film, this symptom indicates powdery mildew infestation. The fungus genus Oidium has specialized on grapevines. This is how you fight the infection in the hobby garden.

The classic symptoms

The fungal spores overwinter within the vines in a mycelium. From spring onwards, they lurk here for suitable weather conditions in order to spread. Warm, humid summer weather with cool nights and warm days is particularly convenient for the parasites, because the dew on the leaves promotes germination. The infection can be recognized by these symptoms:

  • in the first stage, a gray-white coating spreads out on all green parts of the plant
  • both the undersides and the tops of the leaves are affected
  • the leaf veins turn dark and the leaves fall off
  • the still green grapes are covered with a mealy, white patina
  • as the process progresses, the grapes burst open and rot

In the case of continuous rain, the infestation pressure decreases, because powdery mildew on vines is dependent on changing weather conditions.

Biological control of white plaque on grapes

At an early stage of infestation, there is a good chance of counteracting powdery mildew on grapes with natural means. Among home remedies, soda has proven to be quite effective. To do this, dissolve 1 heaped tablespoon of soda in 2 liters of water and add 15 milliliters of curd soap or vegetable oil. Fill this mixture into a hand sprayer and treat the infected grapes every 2-3 days.

In addition, milk has proven to be an excellent way to put an end to fungal spores. Dissolved in water in a ratio of 1:5, spray the mixture repeatedly. Alternatively, add 3 sachets of baking soda and 4 tablespoons of vegetable oil to 5 liters of water. After each downpour, the treatment is refreshed until no white film is visible.

preventive measures

These measures make a valuable contribution to preventing the unappetizing growth of white fungus in the first place:

  • an educational system that is as airy as possible
  • Avoidance of nitrogen-stressed fertilization
  • careful pruning in February and green cuttings in summer
  • consistent weed control
  • Targeted selection of resistant grape varieties

tips and tricks

When using biological fungicides, experienced hobby gardeners ensure that the active ingredient is changed in good time. The oidium fungal spores and all conspecifics have the ability to develop resistance to natural pesticides. Consistent anti-resistance management counteracts this.

GTH

Category:

Vegetable garden