As we enter the apple harvesting season, taking care to prevent damage to fruit and subsequent rot infections is critical. For apple growers, post-harvest molds like blue mold and grey mold can be persistent problems during storage. Blue mold spores are resilient and can contaminate soil, bins, and storage areas, surviving from year to year. Spores in drench solutions can infect apple wounds, while those in storage rooms can get dispersed when apples enter storage. Blue mold spores are commonly found in bulk bins, field crates, packhouse lines, and storage rooms. Fruit injuries, especially during picking and handling, create entry points for spores, which can lead to rapid fruit decay in a matter of weeks.
When it comes to maintaining the quality of harvested fruits, cultural control practices play a vital role. By implementing these key cultural practices, growers can significantly reduce the risk of storage diseases:
- During harvesting, it’s essential to handle the fruit carefully to prevent bruising and wounds, which can make them susceptible to infection by rot-causing fungi.
- Stem trimming can also help reduce potential wounds.
- The maturity of the fruit impacts its susceptibility to storage diseases. Harvesting the fruit at the proper maturity level can reduce the risk of rot during storage.
- In storage, rot pathogens can move on fruit from the orchard or come from plant and soil debris. Clearing the storage bins of old fruit, leaf litter, prunings, and other dead plant material can help eliminate potential sources of rot pathogens.
- Recent research (Jurick et al. 2023) demonstrated that wood bushel storage bins harbor significantly higher Penicillium (blue mold) spores compared to plastic bins. The rough surfaces and crevices in wood bins likely provide conducive environments for spore survival.
- Warm temperatures encourage pathogen growth. To inhibit their development, keep the harvested fruit cool. Placing the bins in the shade can help maintain cooler temperatures.
- For growers delivering fruit to a packinghouse, reducing the time between harvest and delivery can help maintain the fruit’s quality and reduce the risk of rot during transit.
References and additional resources:
- Jurick WM, Choi M, Gaskins VL, Peter KA, Cox KD. 2023. Would You Like Wood or Plastic? Bin Material, Sanitation Treatments, and Bin Inoculum Levels Impact Blue Mold Decay of Stored Apple Fruit. Plant Dis. 107(4):1177-1182.