6 July - Weevils and beetles

Dahlia smut Pale spots usually occur first on the lower leaves during cool, wet conditions. Space crops, improve air circulation and light penetration and reduce leaf wetness periods. Control with Amistar (EAMUs required), Bumper 250EC (EAMUs required), Signum (EAMU 2012-2141) or Systhane 20EW.

Vine weevil Control feeding adults by spraying Chess WG (EAMUs required) or Steward (EAMUs required) during the day and apply Hallmark WZT (non-IPM, EAMU 2008-2944) during late afternoon onto foliage of vulnerable ornamentals for effective control.

Bark-boring beetles Adults lay eggs from July onwards by boring small holes under joints or leaf axils. Eggs hatch and grubs bore into the tree. Suppress adult activity by spraying Decis, Hallmark WZT (EAMU 2008-2944) or Toppel 100 onto stems of vulnerable outdoor-grown trees. Stressed plants seem to attract these types of beetles.

Camellias Continue with liquid feeding for this month only.

Fruit Remove all the fruit from fruit trees before despatch if a non-edible spray programme has been used this season.

Grass weeds For the control of annual meadow grass and some perennial grass weeds, apply Fusilade Max (EAMU 2012-1321) and Laser (EAMU 2017-0473) to a range of outdoor ornamental crops. The optimum time for application is before the tillering of the weeds has started.

Irrigation If aluminium irrigation pipes or irrigators in fields are laid where there are overhead power lines, get staff involved to read the fourth edition of Health & Safety Executive leaflet GS6 for practical advice before getting started.

Mare’s tail Products containing 2,4-D, dicamba or MCPA will give good knock-down control but are safer applied to non-crop areas. Use a hooded sprayer near crops if products containing glufosinate-aluminium are used. With glyphosate, bruise the weed first for better uptake and control.

Iris Control iris corm borers, which cause Erwinia soft rot, using Calypso (EAMUs required), Decis (EAMU 2014-1011) or Gazelle SG.

Scab Warm weather with high humidity increases scab risk on Crataegus, Cydonia, Malus, Prunus, pyracantha, Pyrus and Sorbus. Monitor this risk by using the Mills or Smith tables to calculate optimum spraying times.

Maintenance Service heaters now to check for faults and be ready in time for cooler weather.

SEE HORTICULTURE WEEK'S ARCHIVE OF PEST & DISEASE FACTSHEETS


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