Neonectria ditissima, the causal agent of European canker in apples, conidia are available year-round in the Tasman region of New Zealand. Spore production and release in apple trees were quantified during natural and artificial rain events. Rain traps captured spores over 18 rain events (July—August 2017) from European canker lesions (excised and in planta) derived from ‘Royal Gala’ picking wound and rasp wound infections. Rain traps were monitored regularly to determine spore release over time. Differences in the number of conidia produced from lesions on the tree and excised lesions re-mounted in the tree were not significant. Lesions arising from picking wounds produced 7.2 times more spores on average than lesions arising from rasp wounds. Most spores were released within the first hour of rain and total spore release followed a logarithmic curve. Rain duration × volume of water determined the rate of conidia release. Excised lesions are suitable to study the effect of biotic and abiotic drivers on spore production.

Nitrogen fertilisers are widely used in apple orchards. However, the effects of various nitrogen sources on growth and sporulation of the fungus Neonectria ditissima, which causes European canker, are not fully understood. The effects of various nitrogen sources commonly used in apple orchards (potassium nitrate, ammonium chloride, ammonium nitrate, ammonium sulphate, Nitrophoska® and urea) on percent germination and germtube growth of N. ditissima conidia were tested in vitro. Nitrogen concentrations below 0.2 mol/L did not significantly affect percent conidial germination; however, concentrations above 0.2 mol/L significantly decreased germination. Germtube growth was also affected, generally decreasing with increased N. Percent germination was influenced by the N source, but germtube growth was not. Very low concentrations of urea were indicated to stimulate germtube growth. Higher concentrations, showed toxic effects on both germination and germtube growth. The presence of exogenous N from various sources did not affect initial germination and growth in the N. ditissima infection process of apple tissues.