Potato Grower

September 2018

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WWW.POTATOGROWER.COM 31 "The Industry Leader In Vent Floor Systems" •Better distribution of air fl ow• •Reduces moisture loss by up to 50%• • Low maintenance • Quick cleanup• •Greater storage yield• •Easy storage loading and unloading for onions and potatoes• Currently being used by: Balcom & Moe-Pasco, WA Hartley Farms-Prosser, WA JC Watson-Wilder, ID Oregon Potato-Fruitland, ID Premier Seed-Pasco, WA Sunset Produce-Prosser, WA Target Ag-Othello, WA If you are ready for the BEST air fl oor system ... Please Contact ... Lynn Tegland • 509-529-4898 1243 Reser Road • Walla Walla, WA 99362 (509) 529-4898 • Fax: (509) 527-0390 doubletconstruction@ymail.com www.doubletconstruction.biz •Better distribution of air fl ow• 167863DouTCon16v.indd 1 11/16/17 8:40 AM 1957-25BioSafe13s.indd 1 5/29/18 9:12 AM P. nicotianae, on the other hand, has been detected this season on both potato and tomato crops in North Carolina. P. nicotianae differs from P. infestans in several ways. While both pathogens can infect foliage and tubers, P. nicotianae is primarily a soil-borne pathogen and can infect plant roots. It also has a broader host range than P. infestans and the ability to generate overwintering survival spores including oospores and chlamydospores in the soil. Foliar infections of P. nicotianae resemble symptoms associated with late blight, including large, water-soaked lesions on leaves and stems. This year, foliar blight was severe on potato; tuber rot has also occurred. P. nicotianae lesions generally do not exhibit sporulation. Due to the tendency of P. infestans to sporulate heavily, lesions caused by P. infestans may show a whitish halo on the underside of the leaf where spores can be observed under a hand lens, but this is not present in all infections. Potato and tomato crops with late blight-like lesions should be carefully checked due to the presence of P. nicotianae, particularly in the Southeast. Samples may be submitted to local extension agents or crop consultants for further analysis. P. infestans P. nicotanae Mefenoxam sensitivity Dominant lineage US-23 sensitive to mefenoxam Mefenoxam resistance reported Disease cycle No soilborne phase Soil oospores and chlamydospores Mating types A1 (US-23) dominant; no oospores currently reported in U.S. A1 and A2 common; oospores present Symptoms on potato Tubers, stems and foliage All parts of plant, including roots Asexual survival stages None Chlamydospores Host range Narrow: potato and tomato Wide: potato, tomato, cit- rus, tobacco, ornamentals P. nicotianae does not spread as rapidly across fields as P. infestans due to lower production of sporangia, but adopting a late blight spray program following label recommendations will help manage both pathogens. Consult the control recommendations on the late blight fact sheet or the 2018 Southeastern U.S. Vegetable Crop Handbook for more information on recommended compounds and spray schedules. It is highly encouraged that samples suspected to be late blight are submitted for genotyping by following instructions on the USABlight website. The disease alert and surveillance system also includes additional information on control methods and a decision support tool for fungicide spraying.

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