October 23, 2004
From: ProMED-mail<promed@promedmail.org>
Source: Boston.com News, 20 Oct 2004 [edited] <link>

New Brunswick potato farmers face heavy losses due to weather, pink rot

About a dozen New Brunswick potato farmers are facing millions of dollars in losses due to last summer's wet weather and a warm autumn. Patton MacDonald, Potatoes New Brunswick executive director, said pink rot, which
has affected 10 to 15 farms this year, might lead some farmers to leave the business. He said that the crop on some farms has been lost.

Dr. Khalil Al-Mughrabi, New Brunswick's potato pathologist, said the problem follows frequent and excessive rain, along with high humidity levels during the growing season. An abnormally warm harvest is making it difficult for growers to cool and dry their storage.

Pink rot causes potato flesh to turn from white to salmon pink. The potato is still safe to eat, but it's difficult to market.

91 potato producers are currently enrolled in the New Brunswick Crop Insurance Program, which covers production losses caused by natural perils beyond a producer's control. They produced about 40 per cent of the 2004 crop. MacDonald said that so far, PR is affecting a relatively small number of the province's estimated 300 potato farms.

[Pink rot [PR] is caused by the fungus _Phytophthora erythroseptica_ [Pe]. PR symptoms are typically observed in tubers, but severe infections may develop foliar symptoms such as wilting, yellowing, and aerial tubers. Infected tubers exude a clear, watery liquid and potato tissues remains intact, but are rubbery. Affected tubers are susceptible to bacterial diseases, especially soft rot caused by _Erwinia carotovora_. Pe lives in soil and can infect any below-ground part of the plant. Disease management strategies include avoiding irrigation in the late growing season, particularly if temperatures stay above 75 deg F. Irrigation management and humidity control are crucial to disease control. Potatoes must be sorted so as to isolate infected tubers from healthy ones. Early curing conditions should be 45-50 deg F during drying. Continuous air flow in storage bins is essential during this period. Resistance of Pe to chemical fungicides such as metalaxyl (Ridomil) and mefenoxam has been reported from several locations in the US and Canada, but the majority of the population remains sensitive. Resistance to PR has been noted from Idaho to Maine and east to New Brunswick.

ProMED-mail has no financial interest in Ridomil or similar compounds.

Links: <http://www.gov.mb.ca/agriculture/crops/potatoes/bda04s07(3-4).html>
<http://vegetablemdonline.ppath.cornell.edu/NewsArticles/Potoato_Pink_Leak.htm> -Mod.DH]