Post category: Rust diseases
Many kinds of plants have a rust disease caused by a specific fungus. Brown, yellow or reddish spots appear on the undersides of the leaves, often with a pale green or yellow ‘shadow’ on the upper surface.
Most of these diseases are not fatal to the plants affected, but usually spoil the foliage and reduce growth and flowering. Commonly attacked plants include roses, leeks, hollyhocks, carnations, beans, geraniums, mint, poplars and willows.
Rust diseases have a curious habit of appearing every few years for just one season. If they appear more frequently, and the plants are weakened, spraying might be considered. Usually only roses need to be sprayed. Other plants can be replaced.
Rust disease on raspberry
Suitable chemicals include Dithane and Liquid copper. Use these sprays as indicated above, in early summer, when the disease is first noticed – not as a routine. Repeat the spray twice. Rusts are more common in hot years.