Fernandez, M.R.

Holzgang, G.

Hughes, G.

Pearse, P.

English

University of Saskatchewan Research Archive

9A9B8A5B6A5A6B4A7A7B2B1A8B1B3AS3BN4B2A3BS3ANFig.1.  Saskatchewan Crop districts and soil zonesGrayBlackBrownDark BrownFusarium head blight in wheat and barley in Saskatchewan in 1998 and 1999M.R. Fernandez, ¹, P.Pearse², G. Holzgang², and G. Hughes³¹Semiarid Prairie Agricultural Research Center, Agriculture and Agri-Food Canada, Swift Current, SK;²Saskatchewan Agriculture and Food, Regina, SK;³ University of Saskatchewan , Saskatoon, SK.Overview of Fusarium Head BlightFusarium Head Blight (FHB), also known as scab or tombstone, has the potential of becomingan important disease in Saskatchewan. Since its de.tection in the early 1990's FHB has slowlyspread westward from the Manitoba border through eastern Saskatchewan.  This spread has had anegative impact on yield and quality.  There are many Fusarium spp. that can cause FHB.  The most important ones are  F.graminearum and F. culmorum.  Fusarium spp. produce mycotoxins some of which are harmfulto humans and livestock.  Due to processing problems and potential food safety concerns,tolerance levels for Fusarium damaged kernels (FKD) are very low.  Water-soaked brownish lesions at the base of glumes are distinctive symptoms of FHB. Salmon pink fungal growth is often present along the edge of the glumes to the base of thespikelet.  Because there often is premature death and/or bleaching of infected spikelets,symptoms of FHB are most noticeable before maturity of the crop.Wheat FDK are often smaller, shriveled, bleached, and might have white to light pink moldon them.  However, in barley, disease symptoms are less obvious.Environment plays a very important role in the incidence of this disease.  Conditions of  highhumidity for a minimum of 12 hours are requiredfor infection.  Relatively high temperatures (about25ºC) favour infection by F. graminearum.Cereals are most susceptible to infection atflowering.  Later infections do not cause as muchdamage as those at flowering.  Cereal residues fromprevious crops colonized by Fusarium spp. are themain source of inoculum for head infections.Fusarium head blight survey in 1998-99A province-wide survey was conducted inSaskatchewan in 1998 and 1999 to determine theincidence and severity of Fusarium head blight(FHB).  Number of fields sampled were 68 barley,107 common wheat and 35 durum wheat in 1998,and 60 barley, 168 common wheat and 42 durumwheat in 1999, covering 18 crop districts (CD) (Fig.1).Heads from 50 plants, at milk to dough stages, were sampled randomly from each field andanalyzed at the Crop Protection Lab of Saskatchewan Agriculture and Food.  Heads wereanalyzed for disease incidence (percent number of heads infected) and severity (percentage ofinfected glumes).A FHB index (percent number of heads affected x mean severity of infection/100) wasdetermined for each field.  An average FHB index was calculated for infected fields in each CD,and for CDs grouped by soil zone (Zone I in Brown, II in Dark Brown and III in Black/Gray soil)(Fig. 1).Kernels from infected heads were surface sterilized in 0.05% NaOCl for 1 minute and platedon potato dextrose agar for identification of Fusarium spp.ResultsFHB levels in common and durum wheat and barley in 1998 and 1999FHB was found in most crop districts surveyed, although mainly at low levels, particularly in1999 (Table 1).  Overall, the percentage number of fields where FHB was detected in 1998 and1999 was 60% and 65% for barley, and 55% and 50% for wheat (common and durum),respectively (Table 2).  Percent fields infected was lowest in Zone I (Brown soil) in thesouthwest, and highest in Zone III (Black/Gray soil) in the east and north. Table 1.  Number of wheat (common and durum) and barley fields where FHB was found in 1998 and 1999,and average FHB index for each Saskatchewan crop district.                                                                                                                                                                                                                                                         Crop District                                                                                 Crop/year       1A      1B    2A     2B     3A    3B     4A    4B   5A    5B     6A    6B    7A    7B     8A    8B    9A      9B   _______________________________________________________________________________________________Wheat (common and durum)  1998#fields/total 7/121 6/6 3/6 9/17 1/2 2/15   -²  2/6 4/4 7/9   8/13 3/8  1/7 5/8 5/7 2/5 2/5    11/12FHB index 3.7 1.6 1.4 1.4  0.2  1.5   na 0.5 8.7 8.6 4.1  1.1  0.2 2.0 0.3 0.4 0.9  1.71999 #fields/total   13/14 3/4 1/7   11/21 1/8 0/14  1/7 0/1 4/6 9/19 8/15 6/16 1/8   2/14  13/15  9/13 11/12  13/16FHB index 1.3 0.6  0.9  0.4    <0.1 na     <0.1 na 1.0  0.8  0.7 1.3  1.6 0.3     0.4  1.1  2.0   1.1Barley   1998#fields/total  2/4  2/2 2/2  2/5 0/3 0/4    -    1/2 4/4 5/7  2/4  2/2 0/2 2/4 8/10 1/3 4/4  4/6FHB index 1.9 0.4 0.3 0.4 na na na  0.1 1.5 0.7  0.5  0.6 na  0.3  0.5  1.5  0.4  8.01999 #fields/total   3/4 2/2 2/2 1/3 1/1 1/2 2/4   -  3/3  8/8 3/6 2/6 0/2 2/4 1/1 3/4 4/5 2/5FHB index 0.4 1.0  0.1  0.5    <0.1 0.3 0.1 na 0.4 1.1 3.7 1.7 na 0.1 3.2 0.6 1.4 0.4                                                                                                                                                                                                 1 Number of fields with FHB/total number of fields sampled.2 not sampled.      Overall, the FHB index was low in 1998 and 1999.  On average, it was lower in 1999 than in1998 (Table 2).  For all crops, the average FHB index was lowest in Zone I and highest in ZoneIII.  It was also lower in barley than in wheat in all soil zones in 1998.  Table 2.  Percent wheat (common and durum) and barley fields infected with FHB in Saskatchewan in 1998 and 1999, and average FHB index for each soil zone.                                                                                                                                      Crop/Year                               Zone I ¹           Zone II           Zone III           Mean       __________________________________________________________________                                                               ----------------------------%-----------------------------Wheat (common and durum)1998% fields infected 20 55 77 55FHB index 0.7 2.5 3.4 2.81999% fields infected 8 47 73 50FHB index 0.6 0.9 1.1 1.0Barley1998% fields infected 9 57 78 60FHB index 0.1 0.7 1.8 1.41999% fields infected 44 52 82 65FHB index 0.2 1.3 1.0 1.0                                                                                                                                      ¹Zone I:Brown soil; II:Dark Brown soil; III:Black/Gray soil.                    Pathogens isolated from infected field cropsThere were more Fusarium spp. in Zones II (Dark Brown soil zone) and III (Black/Gray soilzone) than in Zone I (Brown soil zone) (data not shown).  Fusarium poae was the species mostfrequently isolated from infected heads, and was more common in 1998 than in 1999.  Onaverage for all zones,  F. poae was isolated at a frequency of 36% and 23% (common and durumwheat) and 68% and 40% (barley) in 1998 and 1999, respectively.  In 1998, F. graminearum wasthe second most frequently isolated Fusarium spp. (average of 28% in common and durum wheatand 14% in barley).  However, in 1999 F. graminearum was present at lower levels (2% incommon and durum wheat and 11% in barley).  Conversely, the frequency of F. avenaceum wasmuch lower in 1998 (5% in common and durum wheat and 0.4% in barley) than in 1999 (36% incommon and durum wheat and 23% in barley).  The incidence of F. culmorum was similarin1998 and 1999 (average frequency for both years of <10% in common and durum wheat and<1% in barley).  The most important Fusarium spp. associated with FHB, F. graminearum andF. culmorum, were for the most part absent from Zone I in both years. 0 10 20 30 40 50 60 mm1A 1B 2A 2B 3A-S 3A-N 3B-S 3B-N 4A 4B 5A 5B 6A 6B 7A 7B 8A 8B 9A 9B Crop Districts Second week of July0 10 20 30 40 mm1A 1B 2A 2B 3A-S 3A-N 3B-S 3B-N 4A 4B 5A 5B 6A 6B 7A 7B 8A 8B 9A 9B Crop Districts1998 1999 First week of August0 10 20 30 40 50 60 70 mm1A 1B 2A 2B 3A-S 3A-N 3B-S 3B-N 4A 4B 5A 5B 6A 6B 7A 7B 8A 8B 9A 9B Crop Districts Third week of July0 20 40 60 80 mm1A 1B 2A 2B 3A-S 3A-N 3B-S 3B-N 4A 4B 5A 5B 6A 6B 7A 7B 8A 8B 9A 9B Crop Districts Last week of JulyImpact of weather on development of FHB?In most crop districts, the amount of precipitation in the growing season (June through end ofAugust) was higher in 1999 than in 1998.  In both years, there was precipitation in most cropdistricts during flowering, more in 1999 than in 1998 (Fig. 2).  In 1999, flowering occurred thethird and fourth week of July in the majority of crops, however some may have occurred before(beginning of July) or later (into the first week of August) due to variations in seeding dates andcool weather.  In 1998, flowering in most cases occurred earlier than in 1999 (mostly around thesecond week of July).  Weekly precipitation also varied among crop districts.  Because seeding    Fig. 2. Average weekly total precipitation (mm) for Saskatchewan crop districts for 1998               and 1999.was very spread out in 1999, and to some extent in 1998, it is difficult to reach any conclusionsregarding the impact that precipitation might have had on the development of FHB.  However, itis apparent that the amount of precipitation per se during flowering would not explain differencesin FHB development between 1998 and 1999.   Average temperatures for most crop districts during the period crops would have beenflowering, and afterwards, were lower in 1999 than in 1998, except for the last week of July (Fig.3).  Lower temperatures favoured the development of F. avenaceum, a weak pathogen, over thatof F. graminearum in 1999.  Cooler weather prevalent in most of the province in 1999 might alsoexplain the overall lower levels of FHB in 1999 than in 1998.  16 17 18 19 20 21 22 °C1A 1B 2A 2B 3A-S 3A-N 3B-S 3B-N 4A 4B 5A 5B 6A 6B 7A 7B 8A 8B 9A 9B Crop Districts Last week of July13 14 15 16 17 18 19 20 21 °C1A 1B 2A 2B 3A-S 3A-N 3B-S 3B-N 4A 4B 5A 5B 6A 6B 7A 7B 8A 8B 9A 9B Crop Districts Third week of July14 16 18 20 22 24 °C1A 1B 2A 2B 3A-S 3A-N 3B-S 3B-N 4A 4B 5A 5B 6A 6B 7A 7B 8A 8B 9A 9B Crop Districts Second week of July15 16 17 18 19 20 21 22 °C1A 1B 2A 2B 3A-S 3A-N 3B-S 3B-N 4A 4B 5A 5B 6A 6B 7A 7B 8A 8B 9A 9B Crop Districts1998 1999 First week of August         Fig. 3. Average weekly temperature (ºC) for Saskatchewan crop districts for 1998          and 1999.ConclusionsBased on the provincial surveys conducted in 1998 and 1999, FHB remains present at lowlevels in Saskatchewan and it is for the most part localized in eastern and northern areas.  Thesesurveys also confirmed that the development of this disease is very dependent on environmentalconditions.  Although the establishment of this disease in affected areas is believed to have beencaused by higher levels of precipitation in the last decade, the most optimum conditions for itsdevelopment (high levels of precipitation and temperatures) are not common in most parts ofSaskatchewan during flowering of cereal crops.                                                                                                                                                              The following strategies should be adopted in order to prevent the further spread of FHB inyears where environmental conditions favour its development, and minimize crop losses inaffected areas.Strategies for the control of Fusarium Head Blight1) Choice of variety: At the present time, there are no registered wheat or barley varieties thatare resistant to FHB; however there are less susceptible varieties.  Wheat tends to be moresusceptible than barley.  In general, hard red spring (HRS) wheat is less susceptible than CanadaPrairie Spring, durum or winter wheat.   AC Barrie, AC Cora, Katepwa, AC Majestic, McKenzie,and AC Cadillac are the most tolerant HRS varieties.   Two-row barley also appear to be moretolerant than six-row barley varieties.  Two-row malting varieties with  good tolerance to FHBare AC Metcalfe, AC Oxbow, CDC Stratus, AC Bountiful; CDC Kendall has some tolerance. CDC Sisler is the only six-row malting variety with good tolerance to this disease.  CDC Dawn,Condor, CDC Freedom, CDC Gainer, AC Hawkeye, Phoenix and CDC Silky are hulless varietieswith some tolerance to FHB.2) Crop Rotations: A rotation with corn and small grain cereals can increase FHB.  Rotatingwith a non-cereal crop for a minimum of one year, preferably two years, should help to reduceinoculum. However, a crop rotation with a non-cereal crop may not help to reduce FHB infectionif adjacent cereal fields are infected.  Inoculum for infection could also derive from grassy weeds.3) Clean Seed and Seed Treatment: Use of clean seed is especially important in areas whereFHB is not yet a problem.  Producers should avoid purchasing seed from areas where FHB hasbeen a problem in the past.  Lab testing of seed for possible infection by F. graminearum isrecommended.  Seed treatments, when properly applied, may help control poor germination andseedling emergence caused by seed infection.  However, if the seed is infected with F.graminearum, seed treatments might not prevent the introduction of this pathogen to uninfectedareas.  In any case, treatment of seeds would not provide season long control, as inoculum forinfection of heads comes from crop residues and/or infected grasses.  4) Stubble Management: Fusarium spp. surviving on cereal stubble act as a source ofinoculum in the next season.  Encouraging decomposition of residues through chopping andspreading the straw might help to reduce inoculum.  Burying residue through tillage alsoincreases the decomposition rate.  However, residue buried by tillage can later be brought to thesurface and, if not completely decomposed, be a possible risk of infection. These cultural control measures would have a greater impact when levels of inoculum arelow.  Careful inspection of fields to determine the presence and severity of FHB is veryimportant.  A build-up of inoculum might increase the disease levels and reduce the options forcontrol.  Preventing the spread of FHB through the use of clean seed should be the mostimportant control strategy for areas still uninfected.We gratefully acknowledge the participation in the survey of Saskatchewan Agriculture and Foodextension agrologists, technical assistance from Carla Trail and Shanna Stolhandske, and financialsupport by the Agriculture Development Fund.

Fusarium head blight in wheat and barley in Saskatchewan (1998 and 1999)

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Fusarium head blight in wheat and barley in Saskatchewan (1998 and 1999)

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