Aphids: Now present on roses, honeysuckle, hebes and a range of herbaceous plants. There are a lot of parasitised aphids, so continue using products such as Aphox, Chess WG, Majestik and SB Plant Invigorator to encourage natural predators. For black cherry aphid, use Actara (SOLA 2008-2801), Chess WG or Gazelle.
Spider mites: Inspect Ceanothus, Choisya, Convolvulus, Fuchsia, Malus, Picea abies, Fraxinus and roses. Hallmark WZT (SOLA 2008-2944) or Talstar 80 Flo are effective outdoors. For protected crops rotate Borneo (SOLA 2008-1216), Dynamec, Masai (protected roses only), Oberon (SOLA 2004-1718) and Sequel (SOLA 2009-3061). Forest nurseries also have Floramite 240SC (SOLA 2008-2851).
Western flower thrip: This pest continues to flourish on ornamentals under protection. Look out for scratch marks on the top side of leaves or distorted tip growth. On close inspection you can see black frass on the leaves. If you tap flower heads over a sheet of white paper, you often find adults fall out of the flower. Repeated introduction of Amblyseius cucumeris gives good control along with timely sprays of Conserve, Dynamec, Naturalis-L and Nemolt (SOLA 2007-2120).
Whitefly: At the first signs of larvae and adults, introduce Encarsia and Eretmocerus. Chess WG (SOLA 2008-2834), Eradicoat, Majestik, Mycotal, Naturalis-L, Nemolt (SOLA 2007-2120), Oberon (SOLA 2004-1718), Savona and SB Plant Invigorator are all safe with IPM products. Apply products three times, five days apart to get all the hatching eggs and break the lifecycle.
Powdery mildew: Check roses, asters, Solidago, hops, hawthorn and oak seedlings. Clean up the white growth with an eradicant product such as Nimrod or food-grade potassium bicarbonate. Add Cyflamid (SOLA 2007-0512) and Switch along with any older favourites.
Eelworm: Angular patches on the lower, older leaves of Weigela, Philadelphus and Buddleja can mean the presence of leaf and stem eelworm. Do not take cuttings from these plants. Vydate 10G applications (SOLA 1993-0020) will reduce the levels of infection from the pest but render plants unsaleable for six weeks.
Apple scab: Monitor scab risk using Mills or Smith tables to calculate optimum spraying times. Also check Pyrus, Sorbus, Crataegus, Pyracantha and Chaenomeles.
- John Adlam is managing director at Dove Associates www.HorticultureWeek.co.uk/nursery for recent articles