b'TATER TALES Keeping an Eye on Pink EyeHow to save your potato crop from pink eye.PINK EYE IS a sporadic disorder of potato tubers that may result in a significant loss of quality after harvest. The usual symptoms are pink or light brown, slightly raised areas that are easy to see on moist, freshly dug tubers but difficult to find on dry, unwashed potatoes. The affected areas usually occur around the eyes and at the bud end of the tuber. Severe pink eye affects the tuber flesh, reddish-brown decay extends two to three millimetres into the flesh. The rot may be confused EUGENIA BANKS,with late blight, but the tuber rot caused by late blight is potato specialistusually granular and deeper. If tubers are kept cool and with the Ontario Potato Board dry, the only symptom commonly noticed is scaly, flaky skin over the affected areas. Under extreme conditions, the skin develops corky areas before or after harvest, which make the tubers unmarketable for either freshA potato infected with pink rot harvested with pink, puffy market or processing. Pink eye may also cause skinlesions.PHOTO: EUGENIA BANKScracks when the lesions dry out. This disorder is usuallyVerticillium, do not plant varieties susceptible to pink associated with warm, wet soils at harvest, with non- eye such as Superior, Kennebec, Shepody, Yukon rotated fields and with Verticillium wilt. Gold and Pike.Ed Lulai, a renowned potato physiologist with the Reduce soil compactionCompaction results in United States Department of Agriculture, suggestedpoor drainage that increases susceptibility to tuber replacing the name pink eye with Periderm Disorderdiseases and disorders. To minimize wet soils, Syndrome (PDS). The pinkish skin colour is shortdeep till areas where water tends to collect and lived, not causal and often not present. Pink eye mayareas where soils are usually compacted (e.g., field also be found on the tuber surface, not only aroundentrances or head lands). Deep tillage will open up the eyes, so the name is misleading. Lulais studiesthe subsoil that may be impeding proper drainage are consistent with previous findings which showduring wet weather. Improved drainage will limit PDS is due to the death of actively dividing skin cells.periods when tubers will be oxygen deprived and The cells around the dead areas start to divide andthus more prone to pink eye. Also, avoid using heavy expand, but the resulting divisions are disorderly. Deadmachinery when soils are wet. Minimizing water-cells no longer act as a barrier to tuber infection andsaturated soils wont only reduce the likelihood of dehydration, which results in storage problems such aspink eye but will also help limit the development of soft rot or corky lesions. other tuber diseases or disordersAn easy test for PDS is to put tubers under UVKeep available soil moisture below 95 per cent light. The affected areas will fluoresce blue due toduring tuber maturationThis is tricky; soil the accumulation of suberin compounds in areas ofmoisture shouldnt be depleted too much because disorderly skin growth. desiccated tubers are susceptible to blackspot Growers have no control over the high temperaturesbruising during harvest.and the heavy rains that promote pink eye. However,Test diggingDo test digs before harvest to identify there are things growers can do. The best managementareas with high incidence of pink eye. strategies are:Check low spots, wet areas, and compacted areasPractice crop rotationIt helps to increase organicin particularIf symptoms are minor, tubers may matter an important component of soil health. still be marketable. If pink eye symptoms are severe,Manage Verticillium early dyingEarly dyingtubers will be rejected and should not be stored. reduces canopy coverage and loss of canopy allowsTubers with pink eye are more vulnerable to soft rot soils to warm faster on sunny days, thus leading toin storage.higher temperatures that are more favourable forThere are good and bad pink eye years, just try to do pink eye development. In fields with a history ofwhat you can to avoid a bad year.46SPUDSMART.COM Summer 2022'