Rust diseases on raspberries

There are several rust diseases that attack raspberries. Rust diseases often have complicated life cycles that include alternate hosts, and most produce several types of spores. If you see rust diseases on your raspberry crops, it is important to identify which disease is present, so you can manage it effectively.

Late leaf rust (Pucciniastrum americanum)

Crops attacked: Red and purple raspberries

Alternate hosts: White spruce

Symptoms: Pale orange powdery spores on lower leaf surface, upper surfaces develop small yellow areas that gradually turn brown. Severe infections may result in early leaf drop, reduced plant vigor and yield and increased winter injury to infected canes. On fruit, bright orange powder y spore masses develop on infected drupelets.

Control: Prune and trellis raspberries to encourage air movement and rapid leaf drying. Prune out and remove old canes. If possible, remove nearby white spruce which are required for the disease to complete its life cycle. Prebloom applications of Ferbam to raspberries might help reduce infections. Currently there are no other fungicides registered for control of late leaf rust in Ontario.

Comments: Late leaf rust is common in Ontario. While summer-bearing cultivars often escape fruit infections, fall-bearing raspberries tend to develop fruit infections if weather conditions are favourable for disease development. The cultivars Heritage, Jaclyn, and Caroline seem especially susceptible.

Late leaf rust on raspberry leaves

Figure 1. Late leaf rust on raspberry leaves.

Orange rust (Arthuriomyces peckianus and Gymnoconia nitens)

Crops attacked: All raspberry species except red raspberry

Alternate hosts: none

Symptoms: Plants develop symptoms the year following infection. New leaves are stunted, pale and spindly. Bright orange waxy pustules develop on the lower leaf surface, later becoming bright orange and powdery. Infected plants are unproductive.

Control: This disease is systemic - once a plant is infected it is always infected. Remove infected plants, preferably before orange pustules break open and spores spread to more plants. Remove wild black raspberries from adjacent woods and hedgerows.

Comments: Very common on wild black raspberries and blackberries.

Late leaf rust on raspberry fruit

Figure 2. Late leaf rust on raspberry fruit.

Yellow rust (Phragmidium rubi-idaei)

Crops attacked: Red raspberries

Alternate hosts: none

Symptoms: In spring and early summer, yellow pustules appear on the upper leaf surface of young leaves. As summer progresses orange pustules are produced on the lower leaf surface, eventually turning black as the overwintering spores are produced. If infections are early and severe, the disease can cause early leaf drop and reduced winter hardiness.

Control: Purchase clean plants from a certified plant grower. Reduce inoculum by pruning out old canes and cultivating to reduce leaf debris. Several group 3 fungicides, such as Nova, Tilt and Bumper, are registered for control of yellow rust. Apply before symptoms appear.

Comments: This disease is not prevalent in Ontario, although it is common in the Pacific Northwest. Yellow spots on the upper leaf surface can help growers distinguish between yellow rust and late leaf rust, which does not produce symptoms on the upper leaf surface.

Orange rust on black raspberry

Figure 3. Orange rust on black raspberry.

Table 1. Rust diseases of raspberry and black raspberry

Common Name (Scientific Name) Crops Attacked Alternate Host Symptoms Control
Late leaf rust (Pucciniastrum americanum) Red and purple raspberry (common in Ontario) White spruce Orange powdery spores on lower leaf surface, and on fruit. No distinct spots on upper leaf, but eventual necrosis. Crop sanitation, trellising and pruning to assist with quick drying. Remove nearby white spruce.
Orange rust (Arthuriomyces peckianus Gymnoconia nitens) All raspberry species except red raspberry None Bright orange waxy pustules develop on the lower leaf surface, later becoming bright orange and powdery. Remove infected plants. This disease is systemic in plants.
Yellow rust (Phragmidium rubi-idaei) Red raspberry (not common in onatario) None Yellow pustules on upper leaf surface of young leaves. Orange powdery spores on lower leaf surface turning black in late summer. Crop sanitation and use of registered Group 3 fungicides in spring and early summer.

 


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca