Mist: Check the operation of mist systems now and replace defective parts. The leaf sensors should have a surface that is clean and flat and light sensors should have a clean "window". Nozzles that have last year's algae growth on can be taken out and put in a tank of Jet 5 and cleaned up.
Feeding: Keep feeding programmes on bedding and over-wintered herbaceous going. If we reduce watering in the dull times, use every opportunity to maintain liquid feeding when possible. Watch for Botrytis on plants and Rhizoctonia on bedding with earlier high levels of water application.
Whitefly: Control active populations on non-edible crops with rotational sprays of Chess WG (SOLA 2008-2834), Intercept 70WG, Majestik, Mycotal, Naturalis-L, Nemolt (SOLA 2007-2120), Oberon (SOLA 2004-1718), Savona and SB Plant Invigorator, particularly if you are using biological control. Otherwise, consider Actara (SOLA 2009-2801), Calypso (SOLAs required), Decis (SOLA 2007-1693), Gazelle, Spruzit or Toppel 100EC. Check each label because some of these products can be used on edible crops too. Spraying three times at five-day intervals to ensure all subsequent generations are controlled gives the best adult control programmes. Couraze, Exemptor or Imidasect 5GR granules in growing media provide longer-term control for ornamentals.
Drought: Watch for dry pots within a block even at this time of year. Automatic irrigation systems are notorious for being uneven. Avoid mixing up different compost types on the same area or crops of different size - these all add up to variable watering rates in pots.
Slugs: Emerging Hosta foliage makes a wonderful meal for slugs, which can quickly ruin saleable plants. Use Ferramol, which is much safer to the environment and does not look as unsightly as some of the older products. Another product, Decoy Wetex, while a large pellet, does retain effectiveness even in an outdoor overhead irrigation regime.
Western flower thrip (WFT) larva: As the air temperature starts to rise we can expect the activity of WFT larva on foliage to become more obvious. The tell-tale scratching of the foliage can quickly ruin a perfect plant ready for despatch. Control with Conserve and predators as soon as seen. If left untouched the levels can increase and start to cause growing tip distortion.
Lupins: The seed-borne disease Colletotrichum should be kept under strict control. The tell-tale spiralling of foliage with darkened and fallen stems should be kept under close observation and controlled as soon as it is seen with Cercobin WG (SOLA 2008-1384).
- John Adlam is managing director at Dove Associates www.HorticultureWeek.co.uk/nursery for recent articles