Troubleshooting
Knap Hill Scarlet quince problems — and how to fix them
Knap Hill Scarlet quince (Chaenomeles x superba 'Knap Hill Scarlet') is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Fireblight (Erwinia amylovora)
A serious bacterial disease causing shoots and blossoms to wilt and turn brown as if scorched. Remove affected material immediately, cutting 30 cm below visible infection; sterilise tools between cuts. No chemical cure is available.
Brown scale (Parthenolecanium corni)
Oval brown scale insects on stems and branches, causing sooty mould and weak growth. Treat with a plant-oil-based or pyrethrin insecticide in late spring when crawlers are active.
Chlorosis
Yellowing leaves, especially on alkaline soils, indicates iron or manganese deficiency. Apply a sequestered iron foliar feed and acidify the planting area with sulphur chips.
Prevent knap hill scarlet quince problems before they start
Most knap hill scarlet quince issues are care-mismatch, not bad luck. Dial in the basics:
Knap Hill Scarlet quince problems — FAQ
Why is my knap hill scarlet quince fireblight (erwinia amylovora)?
A serious bacterial disease causing shoots and blossoms to wilt and turn brown as if scorched. Remove affected material immediately, cutting 30 cm below visible infection; sterilise tools between cuts. No chemical cure is available.
Why is my knap hill scarlet quince brown scale (parthenolecanium corni)?
Oval brown scale insects on stems and branches, causing sooty mould and weak growth. Treat with a plant-oil-based or pyrethrin insecticide in late spring when crawlers are active.
Why is my knap hill scarlet quince chlorosis?
Yellowing leaves, especially on alkaline soils, indicates iron or manganese deficiency. Apply a sequestered iron foliar feed and acidify the planting area with sulphur chips.