27 November - Algae and weeds

Slippery pathways - The recent spell of warm weather followed by a wet period has allowed the rapid regrowth of a blue/green algae and bubbly-like appearance on pathways and beds. Called Nostoc commune, this organism makes pathways and beds unsightly as well as slippery. Clean up pathways with Jet 5 or container beds with Mogeton.

Heaters - Calibrate your thermostats with external data loggers or other devices - do not just rely on the temperature readings from the computer system. This will save on fuel and avoid potential damage to crops. Ensure that the fans are fully operational to move the warm air around the structure.

Ventilation - Get tunnel and glasshouse doors and vents open when weather permits. Alter the sequence of automatic watering and apply early in the morning rather than at night to allow foliage to dry out during the day. At temperatures of between 10 degsC and 20 degsC, and a humidity of 100 per cent, Botrytis growth is irreversible after three hours.

Perennial weeds - Apply Roundup to persistent perennial weeds in established woody field-grown crops. Chikara, Dow Shield 400 (EAMU 2013-0514), Sumimax (EAMU 2008-2881) or products containing pendimethalin will provide good dormant season clean-up. However, make sure that soils are moist - not waterlogged - and fine for effective herbicide applications.

Spraying Oil - Apply this product to dormant crops that suffered from mite, mealybug and scale insect attack this season. It is an extremely effective winter wash - a good alternative is Savona. However, avoid applications before, during and after frost.

Trimming - Wait until late winter/early spring before trimming plants to avoid any wounded stems and foliage sitting dormant for a long period of time. Crops will be at greater risk of stem dieback and Botrytis if they are trimmed now.

Cleaning up - Protected nursery stock should still be sprayed with Octave, Rovral WG (EAMU 2011-3200) or Switch during the winter period as precautionary disease treatments. Use an air-assisted sprayer, if possible, to get good penetration. Focus applications on Helleborus, Coronilla, lavenders, helichrysum and hebe this month.

Spraying - Apply at least one fungicide spray on tunnel crops this month using Rovral WG (EAMU 2011-3200), Signum (EAMU 2012-2141), Switch or Octave. Use wetting agents for plants with hairy foliage.

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