b'temperatures between 31o to 34o F (-0.5o stems, and a non-uniform stand in theto1.1o C).Thismayoccurwhilethe field. In the field, hot soil temperature iscrop is still in the ground before harvest, the main cause of seed aging. in transit, or in storage.Little potato disorder or no top:NewChillinginjuryisnotvisibleonthe tubersareproduceddirectlyfromthetuber surface but causes pinkish-red to sprouts, without emergence. reddish-brown or gray discoloration oftheflesh.(Thereddish-browndiscol-orationsymptomiscalledmahogany Freezing injury effects on tuber. (JohnNordgaard, Black Gold Farms)browning). The vascular tissue is very sensitive to Frozen Sprouts chillinginjury.Chilledcellsarenot Freezingtemperatureskillemergingfrozen, and tissues do not break down sprouts.Newsproutsregrowfromrapidly.Little potato tuber disorder or no top.healthy tissue emerging at a 90-degree (Andy Robinson, North Dakota Stateangle to the stem. This delays emergence University/University of Minnesota)Chilled potatoes should not be used for for at least a week and stand is not uni-seed. Cut surfaces do not heal properly, form.andseed-piecedecayislikely.Sprouts Hair Sprouts from chilled potatoes usually die off. High soil temperature toward the end ofthe growing season causes this disorder.Hairsproutdisordermaydeveloponphysiologicallyoldtubersalongwiththe formation of little potatoes resultingin poor stands. Hair sprouting is also asymptom of infection with the black dotfungus. (Fig. 13b)Chillinginjurytotuber.(EugeniaBanks, Ontario Potato Board)Frozensproutdamage.(JohnFreezing Injury Nordgaard, Black Gold Farms)Soil temperatures below 28o F (-2o C) forseveral hours kill the tuber tissue closer Hairsprouts.(SteveJohnson,Physiologically Old SeedUniversityofMaineCooperativetothesoilsurface.Symptomsbecome Seedthataccumulatedmanygrowing Extension)visible as the tubers begin to thaw result- degree days or stressed in the field prioringinfreemoisture(weeping)onthe to harvest, was not properly stored, or Blackhearttuber surface.stressed by excessive handling can pro- Canoccurduringtuberdevelopmentducerecognizablesymptoms.Ithas and/orstoragebythelackofoxygen,Later, cellular breakdown causes the tis- sprouts, or second growth, and/or it can leadingtodark,necroticcavities.sue to turn brown, grey, or black. A dis- be spongy or dehydrated. Planting seed Increasedtemperaturecanintensifytinct line is visible between healthy and with these symptoms can result in miss- blackheart, especially after vine kill andfrozen tissue.ingplants,slowemergence,multiple when soils are saturated. Seed with 20 POTATO GROWER MAY/JUNE 2021'