Xiao (Photo by Brian Charles Clark)

The old saying about one bad apple spoiling the whole bunch is based on a real concern. For Washington’s tree fruit industry, postharvest rot of fruit in storage costs the industry millions of dollars of losses annually.

 
Chang-Lin Xiao, an associate professor of plant pathology and extension specialist at the WSU Tree Fruit Research and Extension Center in Wenatchee, has discovered three previously unknown fungal pathogens in the United States that cause apples and pears to rot in storage.
 
Two were the first reports of the pathogens in the world and were described as a new fungal species. These pathogens are responsible for as much as one-fifth of the losses resulting from postharvest decay in Red Delicious apples and one-third of the losses in d’Anjou pears in Washington.
 
The pathogens colonize while the fruit is still in the orchard and remain latent at harvest, but disease symptoms develop during storage. Xiao has been conducting research to address the biology, epidemiology and control of these diseases.
 
“We’ve found that with appropriate pre-harvest or postharvest fungicide treatments we can significantly reduce the postharvest rot problem,” Xiao said.
 
In addition to those new diseases, Xiao has developed rot-control approaches using reduced-risk fungicides to target all major diseases that commonly affect apples and pears in storage.
 
He advocates improved communication between growers and packers to coordinate pre- and postharvest fungicide applications
to reduce rots as well as to avoid development of fungicide resistance in postharvest pathogens. Pre-harvest treatments with different mode- of-action fungicides can reduce the need for postharvest treatments and reduce the odds that pathogens develop resistance to the treatments.
 
For more information about tree fruit research at WSU, please visit:
http://www.tfrec.wsu.edu/