Potato pink eye is a disorder that often starts with pink, water-soaked areas around the eyes of the tuber — that’s why it’s called “pink eye.” But as the tuber matures and the skin sets, the pink areas become thickened, corky patches (called bull hide) or show other marks of skin deterioration like flaky scales, or small cracks, or fissures.
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The damaged areas often have an underlying layer of necrotic, reddish-brown tissue that extends just a few millimeters into the tuber flesh.
Causes
Pink eye is a physiological disorder associated with excessive soil moisture (above 95% available soil moisture) along with high soil temperatures (above 70°F) that result in anaerobic conditions around the tuber during the later stages of potato growth. The lack of oxygen results in damage and death of meristematic (actively dividing) cells that produce the tuber periderm (skin), so the resulting periderm is disordered and incomplete. Under normal circumstances, the periderm is a highly effective barrier to pathogens and dehydration. So, tubers afflicted with potato pink eye usually have secondary issues with tuber-rotting diseases and shrinkage in storage.
Pink Eye and Tuber Rots
Potato pink eye is not caused by pathogens. But the anaerobic conditions that lead to pink eye tend to favor the pathogens that cause tuber-rotting diseases like pink rot, soft rot, and Pythium leak. And the compromised periderm is an easier route to infection for pathogens that usually only find entry via wounds. This explains why potato pink eye is commonly associated with tuber diseases, and why the disorder was once thought to be caused by a pathogen. Tuber diseases that are promoted by pink eye can become so severe that they mask the underlying cause.
A New Name for Potato Pink Eye
Pink eye is a terrible name for this disorder. The pink coloration is usually short-lived, and the disorder doesn’t only affect tissues around the eyes. Moreover, the name is too easily confused with pink rot, a tuber disease caused by a soil-borne fungus, Phytophthora erythroseptica. A few years ago, the potato scientists who study pink eye decided to rename it “periderm disorder syndrome,” and they hoped people would start referring to it as “PDS” for short. This name does a better job of conveying the cause of the disorder, but the new name hasn’t really caught on yet.
Potato Pink Eye/PDS Management
Unfortunately, it is difficult to manage disorders, like pink eye/PDS, that depend so much on environmental factors. We can’t stop unwanted rainfall that saturates soils, or heat waves that raise soil temperature. But there are some management strategies that can help to minimize pink eye incidence or severity.
• Cultivar selection. Some potato cultivars are more prone to pink eye than others; Yukon Gold, Pike, Superior, Kennebec, Snowden, Shepody, Russet Burbank, Russet Norkotah, and Clearwater Russet have been noted for higher susceptibility. If you have had problems with pink eye, it might help to try a different cultivar.
• Don’t plant (or harvest) areas prone to waterlogging. Water tends to accumulate in low spots.
and in areas of high compaction such as field entries and untilled headlands. Tubers growing in those areas are more likely to develop potato pink eye.
• Deep tillage. Deep tillage that breaks up compacted areas and improves water drainage should minimize issues with pink eye.
• Canopy cover. A full canopy shades the soil and helps to moderate soil temperatures. Pink eye is often associated with early vine senescence because sunlight reaches the ground and raises the soil temperature. That’s why managing diseases like Verticillium wilt (or early die complex), and other diseases or conditions that cause premature vine death, can also help to reduce pink eye.
• Careful irrigation. Monitor soil moisture levels and avoid over-watering, especially later in the season when tubers are most susceptible to pink eye. Water needs decrease significantly when the vines and roots are senescing, so irrigation should be adjusted accordingly. This is particularly important when growing cultivars that are susceptible to pink eye. In the last several weeks of potato growth, allow soil moisture to deplete to 70-75% of the available water-holding capacity before irrigating. But be careful not to overly dehydrate tubers right before harvest, especially if the cultivar is susceptible to blackspot bruise.
• Assess pink eye incidence at harvest. If you notice a lot of pink eye at harvest, consider packing or processing the crop immediately or limit its time in storage. Secondary problems associated with pink eye, including tuber diseases and dehydration, tend to increase as tubers are kept in storage.
