Summer is just around the corner and with the arrival of the heat, diseases that affect vine growing are also here. Although their incidence depends on the grape variety and the temperature range, some diseases as downy mildew, powdery mildew or Botrytis bunch rot are more harmful over the summer months. Would you like to learn more about them?
Downy mildew is one of the most known vine diseases, caused by the fungus Plasmopara viticola. It evolves in warm climates (temperatures over 10 ºC) with high humidity, but its incidence increases with rising temperatures. This disease affects all the green organs of the vine, especially leaves and bunches. One of the warnings the vine shows are the spots on the leaves, called “oilspots” because of its oily appearance, along with a white down on the underside. The fungus spores can also infect the bunches, becoming grey and covered in dust. Downy mildew can cause the drying of the leaves, but if the attack happens between flowering and fruit set it can result in the total loss of the bunch.
Powdery mildew, just like downy mildew, is a disease caused by a fungus, Erysiphe necator, that can attack any green organ of the vine. The most favorable climate conditions for its development are temperatures that may vary between 25 to 28 ºC and a relatively high humidity. In case the vine is affected, its leaves get covered by an ash-grey to white powder, just like the bunches. This is where the most important damage is located, since the fungus stops the growth of the grape skin and produces its cracking and the seed drying.
Botrytis bunch rot
Botrytis bunch rot is also caused by a fungus, Botrytis cinerea. It is one of the diseases that causes more damages in humid areas, especially when rains happen during the maturation period of the grape. The fungus penetrates the plant in spring forming conidia that the air or the water disperse. They increase their number until reaching the maximum during the grape ripening or maturity period, which is the most affected organ. Botrytis generates a kind of grey pads on the grapes that will develop into completely covering them, even emptying the inside. This fungus is very dangerous since it severely conditions the quantity and quality of the harvest.
Although they are not the only ones, these three diseases are some of the most dangerous during the summer months. Now you have learnt about them, what can you do to know if your vineyard is safe? All of them show visible signs that reveal that something is wrong, but they may be confusing and not make a correct diagnosis. If you want to get an in-depth knowledge of the microorganisms that inhabit your vines, ask for a WineSeq test and anticipate to them.