Keeping potato vines healthy during the growing season is important. Several diseases can contribute to the early foliar decline, including early blight, brown spot, black dot, and Verticillium wilt, but have you considered if Botrytis is a yield-limiting factor in your fields?  

What is Botrytis? 

Botrytis, also known as grey mould and Botrytis vine rot, is caused by a fungal pathogen, Botrytis cinerea. Botrytis cinerea is opportunistic and easily infects damaged and dying tissues. For this reason, symptoms usually appear at leaf margins, especially leaf tips (Fig. 1), and where infected plant material (Fig. 2), like spent blossoms, has fallen on leaves. 
 
Typical characteristics of leaf lesions include: 

• Wider zones of pale grey are separated by darker, narrow zones (Fig. 2).
• Narrow pale green to yellow zone on the lesion edge (Fig. 2). 
• Shrinking and curling leaves (Fig. 1).
• Grey mycelium and sporulation (moist/humid conditions only) on both sides of the leaf (Fig. 2).

Figure 1. Botrytis symptoms develop on a leaf top in a research trial, ON, 2024.


Figure 2. A Botrytis lesion develops in a research trial where infected grain inoculum has landed on a potato leaflet, ON, 2024.

On stems, light-coloured lesions develop (Fig. 3) and then become hollow and bleached. Mycelium and spores can develop on stems (Fig. 4), and long (one to several centimeters), narrow (a few millimeters), and thin (a few millimeters) black overwintering structures called sclerotia will also develop. Tuber infection is also possible but less common.

Figure 3. Botrytis vine rot lesion developing on a stem in a commercial potato field in PEI, 2024.


Figure 4. Botrytis sporulation on potato stem with Botrytis vine rot in a commercial potato field on PEI, 2024.

This pathogen has a wide host range (more than 200 different plant species!) and survives on dead and dying plant tissues, so it’s always present in the environment.

Which environmental conditions favour Botrytis development?

Botrytis is favoured by humid, moist, and warm conditions:

• Spore production occurs when relative humidity exceeds 90%.
• At temperatures of 18 to 24˚C, a spore can germinate and infect in as little as 5 hours when tissues are wet.
• Growth and spore production declines at temperatures ≥ 28˚C.

 

What can be done to manage Botrytis?

• Improve field air circulation and avoid excessive vine growth.
• Consider irrigating when leaves are already wet (i.e., when dew is present) to avoid extended leaf wetness periods.  
• Manage other foliar diseases and stresses to limit damage to foliage and reduce potential infection points.
• Apply fungicides that target Botrytis – use preventively before infection takes place.
• Ensure good coverage of fungicides – get the product inside the canopy where protection is needed most.

 

Syngenta offers two products that include Botrytis protection:

Bravo^® ZN, a group M fungicide that targets Botrytis vine rot, early blight, and late blight when applied at 0.9L/ac.


Miravis^® Duo, fungicide groups 3 and 7, can be used to control early blight and brown spots and/or suppress Botrytis grey mould and white mould when applied at 0.4L/ac.

For more information, visit Syngenta.ca, contact our Customer Interaction Centre at 1-87-SYNGENTA (1-877-964-3682) or follow @SyngentaCanada on Twitter.

Always read and follow label directions. Bravo^®, Miravis^®, and the Syngenta logo are trademarks of a Syngenta Group Company.