Oral Presentation Australasian Plant Pathology Society Conference 2025

The effect of composting on the survival of Neonectria ditissima and other horticultural pathogens (119766)

Lizelle Vorster 1 , Reiny Scheper 2 , Rebecca Campbell 1 , Monika Walter 3 , Emily Lillington 1 , Norman Petereit 4 , Brent Fisher 2 , Ian Horner 2 , Caitlin Donahoe 2 , Emma Applegate 2 , Mary Horner 2 , Matthew Arnet 2 , Jack Hosking 2 , Sean Husheer 2 , Nari Williams 2 , Kerry Everett 5 , Cathy de Villiers 5 , Shamini Pushparajah 5
  1. The New Zealand Institute for Plant and Food Research Limited, Motueka, Tasman, New Zealand
  2. The New Zealand Institute for Plant and Food Research Limited, Havelock North, Hawke's Bay, New Zealand
  3. The New Zealand Institute for Plant and Food Research Limited, Te Puke, Auckland, New Zealand
  4. Kono Horticulture, Motueka, Tasman, New Zealand
  5. The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand

 

Corresponding author: Lizelle.Vorster@plantandfood.co.nz

 

The most efficient way to control European canker in apples (caused by Neonectria ditissima), is to remove and burn the infected plant material to prevent further inoculum spread. However, the smoke from burn piles, causes air pollution and health problems. A more desirable, effective and practical disposal method for infected tissue is needed. Firstly, the possibility of eradicating viable canker lesions by static, non-aerated composting was investigated. In one experiment, viable canker lesions were placed into mesh bags and buried in freshly chipped apple wood and leaves in 1 m3 bags. In another experiment, lesions were buried in a compost mound covered with black plastic sheets. These compost mounds were watered occasionally to prevent them from drying out. Temperature loggers were buried with the lesions in all experiments, and both large (~10-50 mm) and small (~1-9 mm) lesions were used. Viable canker lesions in mesh bags were also kept in a refrigerator as a non-composting control. The samples were retrieved at monthly intervals and assessed for viable N. ditissima spores on agar. The refrigerated controls remained viable throughout the experiments. Chipping and composting at relatively low temperatures (32–45°C) killed all European canker spores after 12 months. Secondly, the survival rate of six important horticultural pathogens (N. ditissima, Eutypa lata, Phytophthora cactorum, Xanthomonas arboricola pv. pruni, Erwinia amylovora and Pseudomonas syringae pv. actinidifoliorum) in a forced aerated windrow composting system was investigated. Samples of various substrates were buried in fresh (>70°C) and mid-mature (60–69°C) compost at depths of 10 cm, 30 cm and 1 m. Control samples were kept at 7˚C and 20˚C. None of the pathogens survived being buried in compost for 1 week, regardless of depth or compost type, while all pathogens remained viable in the control treatments. Composting can be used as an effective disposal method of infected plant material, provided the temperature-time conditions to eradicate the pathogens are met.