Non-fungicidal Control of Botrytis Storage Rot in New Zealand Kiwifruit Through Pre- and Postharvest Crop Management
Storage rot of ‘Hayward’ kiwifruit, caused by Botrytis cinerea, became a serious problem in New Zealand during the 1980s, costing the then NZ$200 million industry about NZ$10 million per year. Fruit are healthy at harvest and become infected through the picking wound during postharvest handling. Disease symptoms develop after 4-8 weeks of storage at 0°C. Ethylene produced by a single rotting fruit in a tray can cause the whole tray to soften prematurely. Control attempts with pre-harvest fungicides led to resistance in B. cinerea to dicarboximide and benzimidazole fungicides. In the orchard, B. cinerea is visible mostly on flower petals early in the season, although it occurs on all plant surfaces, in understory weeds and in necrotic kiwifruit leaves. Research into storage rot risk factors revealed a relationship between rot incidence and the incidence of B. cinerea on necrotic leaves in the orchard around harvest time. Orchard populations of B. cinerea were quantified by assessing the incidence of necrotic leaf discs that were colonised by B. cinerea after incubation. From this, a predictive system has been developed that can identify high risk orchards. The botrytis problem has largely been solved by vine management that avoids dense leaf canopies. This prevents the build-up of the necrotic leaf tissue on which B. cinerea multiplies. It was also found that storage rot incidence can be greatly reduced by “curing” the fruit after harvest. This involves storing fruit for 48 h at ambient temperature before cooling. Storage rot incidence is also reduced by harvesting fruit when they are more mature (7-8°Bx), as riper fruit are much less susceptible to botrytis than immature fruit. The botrytis storage rot problem has thus been avoided by a combination of pre-harvest orchard management and postharvest handling practices, without the need for intervention with fungicides.
KeywordsNecrotic Leaf Soluble Solid Concentration Kiwifruit Vine Summer Pruning Fruit Development Period
Thanks are due to Zespri™ Group for permission to summarise and present the data contained in kiwifruit industry reports and to the Foundation for Research Science and Technology for funding research presented in this chapter.
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