WSU Extension

Hortsense

Rose
 
Disease
Black mold 
Black spot 
Botrytis bud and twig blight 
Brand canker 
Bullheading (cold damage) 
Common canker 
Crown gall 
Downy mildew 
Powdery mildew 
Rust 
Viruses 
Insect
Leafcutting bees 
Leafrollers 
Redhumped caterpillar 
Root weevils 
Rose aphids 
Rose galls 
Rose leafhopper 
Rose midge 
Roseslug 
Spider mites 
Thrips 
Tobacco budworm 
Western spotted cucumber beetle 



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Caption: Rose bullhead
Photo by: R.S. Byther
  
Rose : Bullheading (cold damage)
(revision date: 4/23/2014)


Biology
Bullheads are the most prevalent when temperatures dip to 53-59 degrees Fahrenheit during early flower development. Low temperatures appear to alter metabolic activity, which results in the abnormal appearance of buds and resulting flowers. Flower buds exhibit a flat-topped appearance and weigh more than normal buds with a pointed tip. The number of short petals and petaloids increases, as well as the amount of secondary florets near the bases of flowers. Baccara, Talisman, and cultivars belonging to the Columbia family are especially susceptible.
Management Options


Non-Chemical Management
  • In spring, prune bullheads and allow new flowers to develop in warmer weather.
  • Do not plant in cold areas, and protect roses from frost.
  • Do not fertilize, prune, or water heavily late into the season. This can encourage growth that cannot acclimate well in autumn.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images

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Caption: Rose bullhead
Photo by: R.S. Byther