23 November - Combatting thrips

Biological control - For winter-long Amblyseius applications for thrip control under glass, apply predator-friendly products such as Majestik or SB Plant Invigorator. Gap-up plants to help predators move through crops. Install yellow sticky traps for monitoring - thrip prefer this colour on dull days.

Protected structures - Tunnels and glasshouses are still providing the right conditions for moth egg-laying as well as aphid, mite and whitefly activity. A few warm days will maintain populations at steady levels for a few more weeks. Begin to include more contact-acting products, which will be more effective as we go into the cooler months ahead. Apollo 50SC can be applied now to control autumn-stage spider mites.

Trimming - Wait until late winter/early spring before trimming plants to avoid 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.

Whitefly - Common chickweed and sow thistles will harbour whiteflies outside and under protection throughout the year. Outdoors, keep weed numbers down by burning off foliage with Roundup. Follow that with a residual mix containing Devrinol and Stomp 400SC (EAMU 2008-2923) to reduce regrowth. Use a hooded sprayer to avoid drift damage.

Ventilation - Open the doors of polythene tunnels on days when the weather permits to reduce the risk of Botrytis. Night-time humidity levels can increase to 100 per cent in closed tunnels so opening the doors for even one hour a day will reduce the risk of infection.

Cleaning up - Protected nursery stock should still be sprayed with Octave, Rovral WG or Switch during the winter period as precautionary disease treatments. Add in a wetting agent for plants with hairy foliage, using an air-assisted sprayer if possible to get good penetration. Focus applications on Helleborus, Cordyline, lavenders, phormium and yucca this month.

Field work - Plough land now, particularly if it is needed for spring planting and prone to waterlogging. Frosts will help to break soils down for better structure next season. If you are in an NVZ, remember that the spreading of organic manures is time-limited. This year there are some date changes of which to be aware, so be sure to check them before you apply.

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