Raspberry Leaf Spot

Overview of raspberry leaf spot

Raspberry leaf spot is perhaps the most common raspberry disease we see in the clinic.

Image of raspberry leaf spot symptoms
Raspberry leaf spot symptoms 

Disease cycle of raspberry leaf spot  

Raspberry leaf spot is caused by a fungus called Sphaerulina rubi.  This fungus overwinters on leaves and canes which then serve as sources of infection in spring.  Young leaves are highly susceptible to this disease, but older spots or lesions produce spores that are readily spread by rain or wind to new tissues throughout the entire season.

Signs and symptoms of raspberry leaf spot

Early infections look like dark green circular spots on new leaves.  As leaves get older, spots become light tan to gray.  Severe infections cause leaves to fall off in late summer and early fall and this may not only reduce your raspberry harvest, but it also makes plants more prone to winter injury.  For pictures, please click on the "Raspberry Leaf Spot" link to the right.

Type of Sample Needed for Diagnosis and Confirmation

The Iowa State University Plant & Insect Diagnostic Clinic can help you to investigate and confirm if you plant has this disease. Please see our website for current forms, fees, and instructions on collecting and packing samples. Contact information for each states diagnostic laboratory for U.S. residents.  If your sample is from outside of Iowa please do not submit it to the Plant & Insect Diagnostic Clinic without contacting us

Management of raspberry leaf spot

Cultural measures that increase air circulation are probably the most effective way to control this disease.  Since this fungus thrives under high humidity conditions, promoting faster drying of leaves and canes after rain can reduce the chances of infection.   The easiest tactic is to start off with properly spaced plants between and within rows, and in established plantings, avoid too many canes per plant. Also, reduce the sources of infection by pruning out old fruiting canes and removing them from the garden.

S. rubi spores produced in lesions are spread by rain and wind-driven rains to young tissues.
S. rubi spores produced in lesions are spread by rain and wind-driven rains to young tissues.
Last reviewed:
October 2021

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on September 1, 2016. The information contained within may not be the most current and accurate depending on when it is accessed.