How many conidia are required for wound infection of apple plants by <i>Neonectria ditissima</i>

Abstract

A series of experiments using potted plants in a glasshouse detached laterals in the laboratory and trees in the fi eld were undertaken to study wound size and number of Neonectria ditissima conidia required to produce European canker infections on freshlymade branch wounds in the apple cultivars Royal Gala and Scilate Th e wound types were needle and pin injuries rasp wounds and pruning cuts Spore concentrations from 102 to 106 conidia/ml and two inoculation methods (droplet and mist) were used Disease expression varied for the different assay types probably due to the conduciveness for infection of the diff erent incubation conditions Overall there was little eff ect on pathogen colonisation and lesion development based on injury type inoculation method or spore concentration &gt;103 conidia/ml For freshlymade wounds such as pruning cuts or rasp wounds only three conidia were required for infection initiation in the glasshouse under highly conducive conditions 12 conidia in the laboratory on detached shoots and 10 to 30 conidia in the fi eld

How much captan is required for wound protection of <i>Neonectria ditissima </i>conidial infection in apple?

“…Large wounds will be difficult to protect from N. ditissima with captan-based fungicides. The effect of wound size is in agreement with earlier work by Walter et al (2016) showing that the larger the wound, the more infection will occur and the shorter the incubation and latent periods (infection to symptom expression and infection to spore production, respectively). A shorter latent period was also observed for picking and rasp wounds than for leaf scars, with disease assessments completed earlier for the former.…”

“…In each plot, 40 picking wounds on spurs (20 either side of the plot) and 20 one-year-old shoots for rasp wound inoculations (10 either side of the plot) were chosen from different trees at random. Two rasp wounds per one-year-old shoot were made as described by Walter et al (2016). Rasp wounds were included as additional wound controls.…”

Neonectria ditissima conidium production and release in planta

“…In the Tasman district of New Zealand, both spore types are readily produced all year round in older lesions caused by wound infections in apple trees . Recent research has also shown that large wounds are more susceptible to infection Walter et al 2016). Spur lesions resulting from picking wound infections dominate in the Tasman apple-growing district followed by shoot lesions from leaf scar infections .…”

Protection of budding wounds in apple nursery trees from European canker

“…Buddy tape prevented infection of chip-buds with N. ditissima inoculum applied immediately after budding, as well as 1 month after budding when the tape had been exposed to the elements for a month. Walter et al (2016) showed that only 3 to 30 conidia were required to infect wounds of various sizes. In this study, approximately 12,000 conidia were sprayed towards each bud, which ensured that even if most of the inoculum missed the wound, the taped buds were still exposed to a very high (a) (b) Figure 2 Budded 'EMLA 9' apple rootstocks, 3 months after budding with 'Royal Gala' and inoculation with a conidial suspension (2×10 5 conidia /ml) of Neonectria ditissima.…”