Black Spot fungus ( Diplocarpon rosae )
Diplocarpon rosae is a black spot fungus disease which occurs on rose. This disease active in spring during moist and humidity and its infection causes defoliation and black spots on leaves, canes and stems.
It spreads very quickly. This disease is contaminated. Water and wind help this disease to spread. Also, if the infected parts of the plant are not removed and the fallen dead leaves also not collected from the ground it will spread to other leaves and infect other nearby plants.
Therefore, this disease must be treated as soon as spotted. The treatment will not cure the infected parts but will slow the spread of infection to other plants.
However, the Aphids which is also commonly known as Green fly also contribute to the weakening of the plant. Therefore, the rose plant is more susceptible to the black spots fungus.
How to treat Diplocarpon rosae black spot fungus disease
There is no treatment to cure this disease but you can avoid it from spreading or prevent from infecting your plants. Araby
Remove infected leaves or any infected parts of a plants immediately as soon as you spotted.
Cut the infected leaves with scissor as shown in image below:
But make sure do not cut the new shooting leaf and bud as shown in image below.
Through them away or burn them but do not keep them in same area as its germs drift by the wind and infect the nearest plants.
Pick up all the infected fallen leaves from the ground. Through them or burn them. Do not keep them in same area.
Do not water on to an infected parts of plant as this will spread to other leaves and parts of plant because the water as well as wind help this disease to spread.
If you want to, you can apply Neem Oil by spraying on to the plant after removing the infected leaves or other parts of plants or before the disease starts to prevent from getting this disease.
you can use Neem oil also for the treatment of Aphids which are also called Greenfly and Blackfly.