August 21, 2015  CapitalPress.com 9 Idaho late blight outbreak now widespread By JOHN O’CONNELL Capital Press RUPERT, Idaho — High humidity and continued af- ternoon thunderstorms have enabled late blight to prolif- HUDWH LQ SRWDWR ¿HOGV DFURVV a swath of southeast Idaho encompassing eight counties, according to potato researcher Jeff Miller. Miller, with Rupert-based Miller Research, is now ad- vising growers in Minidoka, Power, Bonneville, Bingham, Cassia, Madison, Fremont and Jefferson counties to spray fungicides weekly — RU HYHU\ ¿YH GD\V LI VWRUPV roll in and threaten to further spread the spore load. Typically, Idaho’s hot and dry conditions keep late blight in check. Miller has encouraged one grower with severe infection to kill vines early to limit the spore load. In most cas- es, however, he’s found light infections of the devastating fungal disease are scattered WKURXJKRXW¿HOGVDQGKDYHQ¶W spread in clusters, thanks to rigorous fungicide programs. But the even distribution of lesions — brown patches often surrounded by light- green halos — has prevented growers from controlling the spread by killing vines in iso- lated areas. “As of now, it doesn’t look like the blight is to the point of devastation, but you can ¿QG OHVLRQV DOPRVW DQ\ZKHUH \RXJRLQ¿HOGV´0LOOHUVDLG adding it’s become the worst Idaho late blight outbreak he’s witnessed since 1998. In central Minidoka Coun- ty, where his own research ¿HOGV DUH KH¶V PDSSHG ODWH blight covering 15 miles from north to south and 10 miles from east to west. Minidoka County crop ad- visor Gordon Harper has also increased his growers’ fun- gicide programs to weekly, compared with every 14 days in a normal year, using more costly but effective products, and cutting into their already WLJKWSUR¿WPDUJLQV “This is the worst I’ve seen it as far as widespread and IDLUO\HDV\WR¿QGDQGDVELJ RIDFRYHUDJHDV,¶YHVHHQLW´ Harper said. All late blight samples in the state have tested as U.S. 23, the same strain found in the Blackfoot area after heavy August rains last season. Mill- er suspects the current Eastern ,GDKRRXWEUHDNPDUNVWKH¿UVW time the disease has over- wintered in Idaho volunteers, though Magic Valley’s infec- tions apparently originated from another source. The good news, Miller said, is that U.S. 23, unlike other strains, is sensitive to the systemic fungicide meta- laxyl — though he warns the chemical works in living tissue and would be a poor choice for senescing plants. Miller has found late blight has been much slower to in- IHFW¿HOGVLQZKLFKPHWDOD[\O was applied earlier in the sea- son to control other diseases, such as pink rot. Hoping to ensure an ade- quate chemical supply, Syn- JHQWD RI¿FLDOV KDYH REWDLQHG Idaho emergency labels for Ridomil, which contains meta- laxyl, and Revis as standalone fungicides in potatoes. Power County grower Nate Schroeder, whose crop had late blight last year, has sprayed a special gas in empty storages to rid them of residual spores and plans to treat spuds with phos- phorous acid as they head into storage. He also plans to acid-kill vines to limit chances of spores contaminating tubers at harvest. Though Schroeder has seen no evidence of late EOLJKW LQ KLV ¿HOGV WKLV VHD- son, he’s operating under the assumption that it’s present. He’s sticking with a biweekly John O’Connell/Capital Press spraying program, however. “We’re pretty sure it’s -HII0LOOHUZLWK0LOOHU5HVHDUFKLQ5XSHUW,GDKR¿QGVDSRWDWRSODQWZLWKDEURZQOHVLRQVRUURXQGHGE\ out there because it’s every- DJUHHQKDOR²DV\PSWRPRIODWHEOLJKW/DWHEOLJKWKDVEHFRPHH[WUHPHO\ZLGHVSUHDGLQ0DJLF9DOOH\ DQG(DVWHUQ,GDKRSRWDWR¿HOGVGXHWRDFRQWLQRXVVWULQJRIVWRUPVVXSSRUWLQJDQGUHORFDWLQJVSRUHV ZKHUH´KHVDLG 34-2/#18