Biological control (Apple canker)

Research has indicated that biological control of leaf scar infection is at least feasible. The tissues of leaf scars become invaded by various host-specific fungi, common primary saprophytes and bacteria.

  • A strain of the naturally occurring fungal organism Trichoderma atroviride is commercially available to UK apple growers as an EAMU authorisation (Vintec 1890/24). It is applied as a spray to dormant trees (crop stage BBCH 97) once all leaves have fallen. It competes with pathogens for space and nutrients, creating an inhospitable environment for pathogens on the plant surface, and is recommended for controlling Neonectria ditissima. Application should be made at temperatures above 10oC and humidity greater than 70%.
  • Experimentally an isolate of Bacillus subtilis was found to be highly antagonistic to N. ditissima when applied to leaf scars immediately after leaf removal.

In a Growing Kent & Medway funded research project led by Niab collaborating with Agrovista and AM Fresh, investigations focused on amending the roots of newly planted commercial apple orchards with arbuscular mycorrhizal fungi (AMF, PlantWorks) and two Trichoderma based biocontrol products (Trianum-P and Vintec), to assess if they might reduce canker. 

AMF are commercially available for use by growers. They have been extensively studied and are believed to improve soil structure, health, and nutrient and water uptake enhancing tree health, tree growth and resistance to pathogen infection (biotic and abiotic stress). Trianum-P (Trichoderma harzianum) is authorised (2026) for use on protected soft fruit crops under permanent protection full-enclosure structures to control fungal diseases. Vintec (Trichoderma atroviride) is authorised (2026) for use on apple to control canker, but as an overall spray application.

Work was also done to increase the populations of AMF in established orchards by sowing wildflowers (known to support AMF activity) and inoculating alleys and tree rows with AMF.

  • Gala trees amended with 50 ml of AMF and 0.2 g of Vintec had five times lower mortality (<1%) three years after planting compared to untreated trees (>5%). This effect was consistent across six commercial orchards.
  • AMF and Trichoderma treatments did not affect the number of mainstem cankers, which likely originated from nursery infections. 
  • AMF amendment did however significantly reduce the number of cankers on the branches. This reduction was most noticeable on sites with the highest canker and tree mortality rates. 
  • The work to increase populations of AMF in established orchards was also conducted and has shown that both wildflowers alone and wildflowers with added AMF increased AMF root colonisation in all orchards.