EPIDEMIOLOGY OF BROWN ROT (MONILINIA FRUCTIGENA) ON APPLE AND PEAR
X-M XU, AM BERRIE and DC HARRIS
Horticulture Research International, East Mailing, West Mailing, Kent ME19 6BJ, UK
Background and objectives
Materials and methods
Results and conciusions
Brown rot on apple and pear trees first appeared in early-July and increased markedly from late August to harvest. Most of the rots observed on apple and pear resulted from primary infection, all associated with damage caused by birds, insects or growth cracking. The relative importance of these entry sites depended on cultivar, orchard and season. On cv Cox, most of the primary rots were associated with bird damage in 1996; in contrast, in 1997, the proportion of the primary rots associated with growth cracking was higher because of frost injury and unusually high temperatures in the early summer. Brown rot in cv Bramley occurred earlier than in cv Cox. In cv Bramley, earlier rots associated with growth cracking resulted from frost injury or herbicide injury and later originated from bird and insect damage. For pears, most of the primary rots were due to bird damage in both years. More secondary (contact spread) rots were recorded on pear than on apple.
Inoculation of fruits on potted apple trees (cv Cox and Gala) showed that wounding was essential for infection by M. fructigena. The spread from rotting fruit to the subtending spur/shoot occurred within 4 days. The incidence of brown rot depended on the interaction between fruit maturity and wound age: wounds on younger fruits were more resistant to infection than on older fruits and, the older the wound the more resistant it was to infection. Furthermore, the degree of wound age-related resistance was higher on younger fruits than on older fruits. The combined effects of weather, wound age and fruit maturity are currently being investigated.