26 May - Sawfly & fireblight

Sawfly Aquilegia, robinia, older roses on site, Tilia and others are susceptible. Check for small green caterpillars that will defoliate plants quickly. Spray outdoor crops with Decis, Dimilin Flo or Tracer (EAMU 2008-2908).

Fireblight Check Rosaceae subjects, especially those that bore flowers last year. Prune and burn all suspect plant material. Cold damage and old scab infections produce similar symptoms.

Mulches Apply bark mulch to compost surfaces ensuring good coverage to retain moisture and prevent weed infestation. Coir mats, polythene slips, grit and shredded miscanthus are also available in varying quantities.

Bees Check product labels for specific information on bees and only spray when they are not foraging - early morning or late evening, depending on weather conditions. Notify local beekeepers if spraying flowering crops.

Feeding Change to high-nitrogen liquid-feed products on nursery stock using 2:1:1 on sprinkler systems and 2:0:1 on drip systems. Avoid applications on warm, sunny days to prevent unnecessary scorch. Add the second top dressing of nitrogen to tree crops according to your fertiliser programme, but do not exceed 50kg per hectare of N (150kg/ha ammonium nitrate).

Plant growth regulators (PGRs) Incorporate PGRs as part of your production routine to increase branching, reduce trimming, improve colour and enhance flowering.

Scale insects Control on Aesculus, Camellia, Laurus nobilis, Hedera, Ribes and Taxus with Chess WG (EAMUs required), Decis (non-IPM, EAMU 2014-1011), Hallmark WZT (non-IPM, 2008-2944), Pyrethrum 5EC, SB Plant Invigorator or Spruzit.

Rust Check campanula, fuchsia, hollyhocks, hypericum, iris, mahonia, Mentha, rose and vinca. Protect foliage using Systhane 20EW. Amistar (EAMU 2017-0965), Bumper 250EC (EAMUs required) or Signum (EAMU 2012-2141) will control infections. Products in FRAC group 3 can produce unwanted growth-regulant effects.

Fusarium Apply a preventive spray to dianthus crowns using Cercobin WG (EAMUs required), Octave, Prestop (EAMU 2015-2773), Serenade ASO (EAMUs required), Signum (EAMU 2012-2141), Switch or T34 Biocontrol (EAMUs required). Improve airflow in protected structures and try not to overwater.

Leaf miners Control leaf damage from larval feeding on protected non-edible crops using Dacnusa and Diglyphus wasps or apply Calypso (non-IPM, EAMUs required), Dynamec or Hallmark WZT (non-IPM, EAMU 2008-2944).

John Adlam, Managing director, Dove Associates

HorticultureWeek.co.uk/nursery


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