Q Why are there tiny white or yellowish flecks on the upper surfaces of my grapevine's leaves? The leaves are starting to discolour and there's some fine webbing.
A Your grapevine is being attacked by red spider mite.
Caption: Red spider mite causes grape leaves to discolour.
Q Why are there are white, fluffy blobs on the grapevine's stem and in the leaf axils. There's black sooty mould on some of the leaves too.
A Your plant has got mealybugs.
Caption: Mealybugs get into nooks and crannies on grapevines.
Q Why are there are convex, brown, shell-like scale insects, each up to 5mm long, on the rods, particularly
on relatively new growth.
A They are brown scale.
Caption: Brown scale colonise grap rods.
Q Why do the leaves have a powdery white coating and the fruits have a tough, greyish coating and aren't developing properly.
A The symptoms are caused by powdery mildew.
Q Why are the individual fruits within the bunch of grapes are failing to colour up in the usual way; green varieties remain translucent and black varieties become red. If eaten, these grapes usually .have a rather sour and watery taste. The affected fruits are also starting to shrivel.
A The fruits have got shanking.
Caption: Shanking ruins bunches of grapes.
Q What are the dark-brown lumps that have appeared on the stems. Towards the end of spring, they produce a thick mass of waxy white fibres containing minute eggs. They produce sticky honeydew, which attracts a coating of black sooty moulds on the leaves.
A They are woolly vine scale.
Q Why are the fruits covered in grey fuzz?
A They have grey mould (botrytis).
Caption: Grey mould causes grapes to rot.
Q Why are there raised, blister-like patches on the leaves from mid-spring onwards? The concave area beneath each raised patch has a dense covering of creamy white hairs, which is darkening as the season progresses.
A Your grapevine has vine erinose mite.
Caption: Vine erinose mite affects grape leaves.