Pears: Flesh Spot Decay (FSD) of Japanese Pears

Core Breakdown | Flesh Spot Decay | Internal Browning | Senescent Scald | Watery Breakdown

Occurrence
Japanese pear cultivars such as ‘Shinseiki,' ‘Nijisseiki,' ‘Kikusui,' and ‘Hosui.' FSD is more frequent on large size (300 g) and overmature fruit.

Importance
FSD limits opportunities to grow and market Japanese pears.

Symptoms
Partial browning of spots and/or development of cavities in Asian pear flesh. It appears along and around the vascular bundles when the symptoms are severe, but there is no external indication of the disorder. Generally, FSD is more pronounced above the equator of the fruit (towards the stem end), but it can also be observed all the way down to the calyx. Cavities are usually dry and surrounded by apparently healthy tissue. This disorder can occur in fruit while still on the tree. It is more obvious, however, after 2-6 week cold storage.

Causes
The cause of FSD is still unknown. However, climatic factors, such as a fluctuating hot and cool summer, or high rainfall right before harvest may enhance the incidence of this disorder.

Control
There is no effective way to control FSD since definite causes have not been identified. The problem is the inability to predict or diagnose FSD without cutting the fruit. Further research needs to be done to determine the causes, variety susceptibility in local climates, and other control methods either pre- or postharvest that will reduce FSD symptoms to a commercially acceptable level.

Meanwhile, avoid whenever possible the following conditions that might induce FSD: low crop load - large fruit; later picking - advanced maturity; extreme temperature changes during the maturation season; sunburn; erratic irrigation or precipitation - frequency, amount and timing; harvesting fruit under warm temperatures and cooling the fruit rapidly.

References
Griggs, W. and B. Iwakiri. 1997. Asian pear varieties in California. Univ. of California DANR Publ. 4068, Oakland.

Lallu, Nagin. 1990. Fruit growth, handling and storage, p. 53-74. In A.G. White (ed.). Nashi, Asian pear in New Zealand, DSTR Publishing, Wellington.

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