b'It is difficult to forecast for specific fields due to highly variable geo-environmental conditions, but every year there are periods of high risks for late blight, especially in low lying spots and wind-protected areas and after thunderstorms, when inoculum can travel many kilometers, says Bisht. It is important to scout for the disease in low lying spots and areas close to tree lines or under high tension hydro-power lines, where aerial application of fungicides is difficult.Slow emergence due to cool soils could also have been responsible for higher than normal blackleg and bacterial stem rot incidence in many Manitoba fields last year, while warm and wet conditions at harvest meant many potatoes hadPotato suffering pink rot infection, which was partly responsible forfrom late blight.PHOTO: KHALIL I.some rotting in storage. AL-MUGHRABIGrowers should scout regularly for crop health and pest issues with Bisht recommending they follow the late blight risk forecast, which is posted online at www.mbpotatoes.ca.Based on late blight risk forecasts the fre- Aphid monitoring on seed potato crops willGrowers should inspect seed potatoes within 24 quency of fungicide applications could be extended,continue, says Bisht. Aphids are efficient vectorshours of delivery by cutting a sample of tubers and saving on costs and reducing pesticide usage,of potato viruses from plant to plant, and couldlook for reddish brown dry rot, which is a character-or shortened when the risk is high, says Bisht.eventually affect the seed potato quality, he says.istic of late blight tuber rot.We also post other disease and insect monitoringOften there is an influx of the aphids and leafhop- When growers purchase seed, Al-Mughrabi reports on this site. pers with winds from the south. recommends they have it tested for the absence of Its also important to confirm the cause of anyblighted seed by an authorized provincial service in unrecognized pest issue and samples, which canATLANTIC CANADA GROWERS SHOULDtheir region. Growers should grade seed potatoes be sent to the Manitoba Crop Diagnostic Centre inTHINK ABOUT BLIGHT MANAGEMENT after being cut to remove any late blight infected Winnipeg, Man. for diagnosis.In Atlantic Canada dry conditions resulted in sometubers which can be a potential source of early incidences of early blight during last years growinginfections in the field. They should also disinfect LOOK OUT FOR COLORADO POTATOseason, but low moisture and a lack of inoculumseed cutting equipment frequently and immediately BEETLE AND APHIDS meant diseases like late blight were absent. Inafter cutting, treat seed with a recommended Normally, during warm and dry conditions, insectareas with abundant rain during harvest though,mancozeb-based seed piece fungicide.populations become an issuesurprisinglysome storage diseases such as Pythium leak, pink though, the levels of various insect pests was lowrot, dry rot and soft rot, were found.MANAGING EARLY BLIGHTlast year in Manitoba. For 2020, these diseases could cause issuesFor early blight to occur, alternating dry and wet In potato crops, we conduct monitoring surveysduring the growing and storage seasons, saysweather conditions stresses plants and triggers the for European corn borer, aphids (seed potato crops)Khalil Al-Mughrabi, pathologist at the Potato Devel- disease. To avoid early blight infection, Al-Mughra-and aster leafhoppers. In 2019, we found low levelsopment Centre with the New Brunswick Departmentbi suggests growers plant resistant varieties, use of these pests, says Bisht. of Agriculture, Fisheries and Aquaculture.blight free seed and destroy potential sources of Colorado potato beetles continue to be an in- If weather conditions change and becomeinoculum such as cull piles and volunteer plants.sect pest of concern in some areas of the province,conducive to late blight disease, this disease canIf conditions are favourable for early blight, mainly due to occurrence of populations resistantre-establish itself very quickly, he says. We havegrowers should start a fungicide spray program to commonly used insecticides, says Bisht. Thebeen warning growers in New Brunswick to stay vig- early, before rows fill in, following provincial recom-review of group 4A insecticides is another swordilant and not to let their guards down when it comesmendations, Al-Mughrabi says. Vines should have hanging on loss of options for CPB control. to protecting their crops against late blight. been dead for at least two weeks before harvest to European corn borer (ECB) could continue toCool nights and warm days, with relativepermit tubers to mature, and care should be taken be a minor pest on potatoes. Bisht is one of thehumidity in excess of 90 per cent are conditionsto avoid bruising in handling. Any tubers left on the researchers involved in a new, national monitoringare favourable for late blight development if thesurface of the field should be left to freeze and not program for ECBs in corn and potato crops underinoculum is present. disked or plowed under. the Canadian Food Inspection Agency Plant HealthGood late blight management begins withBalancing fertilizer is important to prevent Initiative and Surveillance Program. planting disease-free seed, Al-Mughrabi says.delayed maturity or increase susceptibility to early SPRING 2020 SPUDSMART.COM 25'