Mycosphaerella: varieties and crop protection recommendations

This information was last updated in 2015.

Reducing the risk of this disease can be done by using resistant cultivars and through the use of biocontrol agents and fungicides.

Varieties

No genes showing resistance to Mycosphaerella have been found.

In terms of susceptibility to Mycosphaerella, differences between cultivars are mostly caused by differences in flower size and the general growth habit of the crop.

Some cultivars are more susceptible to stem infection, but not to internal fruit rot.

It is generally thought that cultivars with small flowers are less susceptible to internal fruit rot. Probably because the flowers attract fewer spores, but there is no scientific proof for this.

Development rate

The development rate of the fruits is a factor: cultivars with faster fruit development are less susceptible to internal fruit rot.

The widely-used cultivar Proloog (Rijk Zwaan) can be affected by stem infection, but is not very susceptible to flower infection and internal fruit rot.

Other cultivars

Other suitable cultivars are Laureen and Sheila. You should check with marketing organisations, though, as fruit size tends to be smaller than normal.

New cultivars are being developed and susceptibility to Mycosphaerella is an increasingly important factor in the selection process.

Biocontrol

Mycosphaerella spores take in nutrients from the plant surface when they germinate. Their germ tubes grow on the outside plant surface before infection.

Germination and superficial germ tube growth are phases in which biological control agents can be effective. This happens either by competition for nutrients or by excretion of various metabolites that affect the germ tubes.

Biocontrol agents that induce general disease resistance in the plant can be expected to have some activity against Mycosphaerella.

Commercially available agents

Several biocontrol agents with these modes of action have been developed into commercial products: Prestop (Gliocladium catenulatum), Mycostop (Streptomyces griseoviridis) and Serenade (Bacillus subtilis).

Tests have shown that, of these, only Prestop has some effect against Mycosphaerella.

The only other biocontrol products approved for disease control on cucumber are Coniothyrium (for Sclerotiniacontrol in soil crops) and Ampelomyces (AQ10 for powdery mildew control). 

When using these products, it is important to choose conventional chemical fungicides and insecticides that do not harm these biocontrol agents.

Fungicides

Recent experiments showed some success where Switch is used to control other diseases.

Strobilurins (QoIs) have been effective in the past, but currently control is generally poor because of developing resistance within this group of fungicides.

Not all products have been tested for efficacy against Mycosphaerella.

Mycosphaerella may use the wounds/damage caused by other pests and pathogens for easier entry of the plants.

It seems, in this regard, particularly important to control pests that affect flowers.

Please note that this information was last updated in 2015. Biocidal and plant protection products must only be used in accordance with the authorised conditions of use. Regular changes occur in the authorisation status of biocides and plant protection products. For the most up to date information, please check with your professional supplier, BASIS registered adviser or the Chemical Regulation Division (CRD) of HSE (https://www.hse.gov.uk/crd/) before use.

While the Agriculture and Horticulture Development Board seeks to ensure that the information outlined on this page is accurate at the time of publishing, no warranty is given in respect thereof and, to the maximum extent permitted by law the Agriculture and Horticulture Development Board accepts no liability for loss, damage or injury howsoever caused (including that caused by negligence) or suffered directly or indirectly in relation to information and opinions contained in or omitted from this information.

Authors

This information was originally authored by Aleid Dik and Martin McPherson