Quick Questions
Can you identify the leaf problem spreading through my pear tree?
Baz Murray, by email The blackening of the leaves is due to the pear blister mite ( Eriophyes pyri), a microscopic gall mite that feeds inside the leaf. Raised blotches start off pink or yellowish-green, but later turn black. It doesn’t affect cropping or the health of the tree, which is just as well, as there are no effective insecticides against mites. If just odd shoots are affected prune them out.
How do I propagate my dendrobium orchid from the small plantlets on the stems?
Margaret Hamilton, by email Under low-light levels, dendrobiums produce new plantlets, known as ‘keikis’, on the main stems. Once three or four roots form, sever the stem 2.5cm (1in) above and below the plantlet and pot into an orchid compost. Keep well watered, but out of direct sun until established.
Is it OK to treat blue mould on my lifted bulbs with sulphur?
Martin Hewitson, by email Sulphur no longer has approval for use as a fungicide. Ensure your lifted bulbs are thoroughly dried off before storing them. Remove any damaged bulbs and any displaying obvious symptoms. Store in trays in a warm, airy location until you replant.
Can I save my pieris?
Michael Wilson, Keighley, W Yorkshire Pieris are more droughttolerant than other ericaceous plants, but you need to increase watering to at least twice a week in summer. They’re prone to pieris lacebug a ack, which bleaches the foliage, but this is associated with lots of debris and stickiness on the underside of leaves.