Bayer: Botrytis in grapes | Supplier Scene Aug 2020

by | Aug 3, 2020 | Article

The fungus Botrytis cinereal (derived from the Ancient Greek word “botrys”, meaning “bunch of grapes” and the new Latin suffix “-itis”, meaning inflammation) is also commonly referred to as grey mould. It’s a necrotrophic pathogen that induces cell death of its host and lives on dead plant material.

Infection occurs in one of two ways: The pathogen enters the plant tissue through wounds caused by for instance hail, bird or insect damage or it’s latent in the grape and develops once conditions are favourable.

The disease can cause bunch rot close to harvest, resulting in production losses pre- and post-harvest. In wine grapes Botrytis produces enzymes that reduce the flavour, colour and storage quality of wine. In table grapes shelf life is reduced, and sorting and packaging costs are increased.

About the problem

Strands of the mycelium (fungus) produce hard structures called sclerotia which survive on the vine and decaying matter in the soil. The mycelium and sclerotia can survive for up to 20 months under favourable conditions and on various other vegetative growth in or near the vineyard so weed control, for example, also forms part of disease control.

Both these structures can produce spores for new infections. Spores are transported by wind or water to infect vines and the pathogen germinates in as little as one hour. Prolonged wet periods combined with cooler weather in spring give rise to the development of Botrytis. Although temperatures of about 20 ˚C favour development, the pathogen can survive in a temperature range as wide as 1-30 ˚C.

Dense canopies aggravate disease development. Some varieties are also more susceptible due to thinner skin and dense bunch formation which promotes moisture retention. The most susceptible stage is the flowering period. Control during flowering is critical as once the pathogen penetrates the berry control becomes difficult.
Luna
® Privilege offers ideal control during the flowering stage.

Post-veraison is also an infection-prone stage as increasing sugar production and sugar leakage from berries can promote growth of Botrytis on the surface and latent infections inside the berry.

All stages can however be infected.

Control

Certain preventive actions can minimise Botrytis risk.

These include:

  • Plant establishment.
  • Positioning of row direction to optimise airflow through the vineyard.
  • Spacing plants to improve airflow.
  • Using trellising to improve airflow.
  • Correct irrigation selection.

As Botrytis is a weak pathogen a vigorous plant is
more tolerant to infection.

Sanitation

  • Weed control.
  • Removal of old plant debris.

Crop protection

  • When applied during flowering, Luna®Privilege controls Botrytis at several stages of the life cycle, including spore germination, germ tube elongation, mycelial growth and sporulation.
  • Teldor® inhibits germ tube elongation and has a short withholding period.

Botrytis is genetically highly adaptive and is known to develop resistance by means of its genetic mutations. Various modes of action are thus needed to effectively control the pathogen. Optimal timing for application and the correct product for the specific growth stage are critical to obtain the most benefit from your chemicals. Always follow label guidelines.

Symptoms

Typical symptoms include a greyish mould on the grapes, hence the common name grey mould (photos 1 & 2).

Leaf symptoms start as dull green spots turning necrotic (photo 3).

  1. Grey mould  2. Leaf symptoms 3. Grey mould

Handy tip

To detect early symptoms on darker grapes lightly press on the light-brown discolouration of skin. If Botrytis is present the skin simply slips off. Later symptoms are the visible conidiospores visible on the grapes (photo 1). As the disease spreads it can form a “nest” inside the bunches.

Basic programme

 


Teldor
®
(75 ml/100 litres @ 1 000 litres/ha)

Luna®Privilege
(35 ml/100 litres @ 1 000 litres/ha)

Luna® Privilege Registration number L8997 (Act 36 of 1947). Luna® Privilege contains Fluopyram (Caution). Scala® Regisgration number L4972 (Act 36 of 1947). Scala® contains Pyrimethanil (Caution). Teldor® Registration number L6250 (Act 36 of 1947). Teldor® contains Fenhexamid. Luna® Privilege, Scala® and Teldor® are registered trademarks of Bayer AG, Germany. Use strictly according to label instructions.

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