b'What causes most cases of fusarium headWhat challenges exist in regard to cropblight, in your experience? rotations?Historical outbreaks of FHB can be tracedAt least two years before growing a host to several causes: widespread planting ofcrop is crucial. The wheat-canola rotation highly susceptible cultivars; presence ofis not sufficient. Problem is, a producer Kelly Turkington F. graminearum-colonized residue fromneeds a suite of crops they can grow and Research Scientist - Plantprevious crops; presence of corn in rota- market successfully. Pathology tion with small grains; weather favourable AAFC Lacombe for infection. What role does harvest management play?One of Kellys areas ofA number of techniques exist to reduce expertise is studyingHow has it progressed on the Prairies, espe- the potential for downgrading due to FHB management, andcially Alberta? fusarium damaged kernels and/or the previously genetic changesPrior to 2010 in Alberta, we had fairly lowrisk of FHB in subsequent crops. Blowing in the Canadian Fusariumlevels. Fast forward to 2012 and we had aout fusarium damaged kernels from the graminearum population andwatershed year. In 2016 it was a bannerback of the combine is one. In wheat this their effect on pathogenicity,year for FHB from a pathology perspec- helps to improve grade and reduce DON. toxin production, fungicidetive. Eighty-five to 90% of SaskatchewanProblem is, you may be blowing back on sensitivity and disease spread. and Manitoba Canada Western Red Springto the field plant tissues (kernels and head (CWRS) samples had fusarium damagedtissues) that are the most prolific produc-kernels in 2016, respectively, while 33% ofers of wind-dispersed spores. Postharvest Alberta samples had damaged kernels. Ingrain cleaning may avoid this. Harvest Manitoba and Saskatchewan the lions shareweed seed destruction via Australian and of FDKs are due to F. graminearum. ThisCanadian technology may help to lessen pathogen is still not the dominant fusariumthe risk associated with blowing fusarium species in Alberta, with the exception ofdamaged kernels out the back of the durum wheat. In southern Alberta the lionscombine, as it grinds the damaged kernels share of FDKs in durum wheat would bealong with weed seeds. This will help to due to F. graminearum. Unfortunately, thefacilitate decomposition of fusarium dam-picture in the province has been changingaged kernels and associated tissues.over the last five years or so.How can a grower get the most out of fungi-What risk does infected seed present? cide application?Seed is a vehicle for introducing F. gra- Currently the recommendation is to apply minearum and other seedborne pathogensit when 75% of the wheat heads are fully into areas where its never been foundemerged to when 50% of the heads on or was found infrequently. If you have athe main stems have visible anthers. So source of infected residue, it doesnt meanwhat does it mean if you apply fungicide youll have issues with FDK or DON for FHB when 75% of the heads are fully you need to build up infected residue untilemerged? Seventy-five per cent of the you see perhaps at least 25-50% of lowerheads come in direct contact with fungi-stem nodes having detectable levels of F.cide and have some protection, while 25% graminearum. Seed treatments may helpof the heads receive no fungicide and are but dont eliminate potential for seedingnot protected at all.to seedling transmission. If you look at threshold recommendations for seed treat- Does this fit into current fungicide schedules?ments in the U.K., you can have up to 10%My own feeling is if were looking at both seed infected with F. graminearum beforeFDK and DON management, we may need you need to use a seed treatment. Yourto look at a change in mindseta little seed testing report will indicate if you havelater application. That would require a issues with germination and vigour, so youchange in regulations to widen the labels. need to look at those test results in addi- We may need to look at chemistries that tion to any fungal pathogen screens thatprovide a longer level of protection. are done.NOVEMBER 2020 GERMINATION.CA 43'