Sustainable Growing

Grey mould – an autumn threat to crops

Krzysztof Fatel
January 16, 2024

Botrytis cinerea (Persoon) – another name for the teleomorph of Botryotinia fuckeliana (de Bary Whetzel), a fungus that causes grey mould and is a polyphage virtually attacking all dicotyledonous plants, including all vegetable crops grown in fields and under shelters. It is among the top ten pathogens in terms of damage to agricultural production. This pathogen overwinters in the form of sclerotia, conidia or mycelium in soil and on plant remains. This fungus infects plants primarily through wounds, as well as directly through undamaged covering tissue. At the first stage of infection, it kills the infected tissue and then colonises it. It forms a dense and highly powdery layer of conidia on dead parts of a plant. Over time, black sclerotia grow that and can survive in soil during winter or periods unfavourable for infection.

Botrytis cinerea grows most rapidly under the conditions of high humidity (RH>85%) and at temperatures of 15-20oC. In general, crops in shelters are at risk throughout the production period, but for many reasons it is on the 25th of July that a period starts when diseases and infections tend to develop. The pathogen described is distinguished by its high variability, for example enabling it to rapidly develop resistance to available fungicides in use.*

Above all, prevention of grey mould in greenhouse crops requires:

  • An active climate to be maintained, including humidity and air temperature, forced air movement and ventilation in the facility, as well as condensation prevention;
  • Meticulous care of plants (to minimise mechanical damage to plants) and carrying out care work, such as leaf cutting under favourable climate conditions indoors, as well as spotting and eliminating infected plants;
  • An appropriate irrigation strategy to keep the root system and plants in good condition, making them generative;
  • Adequate fertilisation (especially using Ca, K, Si);
  • The use of microbial fungicides;
  • The use of chemical plant protection products in the event of intensifying disease symptoms.

Principles of autumn crop irrigation to reduce the incidence and development of grey mould

  • Irrigation START based on plant activity ↓WC as from sunrise 1.5 - 2%
  • Irrigation STOP ↓WC until sunset amounting to a minimum of 3%
  • Daily decrease ΔWC in the humidity of the substrate of at least 8% in August
  • As from September more than 10%
  • WC of the substrate: for tomatoes 60% during the day and 50% at night; for cucumbers: 65%;
  • EC of the substrate at a stable level
  • June / August between 4.0 – 4.5 mS; after plant head cutting – 5.0 – 5.5 mS ECslab- Ecgift = 1.0 or 1.5 mS/cm

An irrigation strategy can affect the reduction of grey mould of crops. As of the end of July, special attention should be paid to irrigation starting and ending times which determine the night drop in the water content. In autumn, night irrigation is an occasional necessity, e.g. due to special weather conditions.

Optimizing nutrition to minimize fruit quality disorders

Maintaining a good nutrient balance in the root zone can help avoid many common fruit quality disorders. Standard feed recipes are available from all analytical laboratories and with a regular analysis of the root zone solution the feed solution can be adjusted so that optimum nutrient ratios are maintained.

Where the magic happens: unlock the potential of data driven decision making

Data science and AI technologies present us with so many opportunities to collect and mine data in the greenhouse. This paper will help you begin your journey to get the best out of your greenhouse data. There’s a bright future ahead!