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Effects of foliar fungicides on kernel black point of wheat in

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                        Disease control


                  Effects of foliar fungicides on kernel black point
                  of wheat in southern Saskatchewan
                  H. Wang, M.R. Fernandez, F.R. Clarke, R.M. DePauw, and J.M. Clarke



                  Abstract: This study was undertaken to determine the effect of fungicides on the incidence of black point in wheat
                  (Triticum spp.) in southern Saskatchewan, Canada. Experiment 1 was conducted at Swift Current and Indian Head for
                  3 years. Folicur 3.6F (tebuconazole) and Bravo 500 (chlorothalonil) were applied at different growth stages from stem
                  elongation to head emergence. Three spring common wheat (Triticum aestivum) and three durum wheat (Triticum
                  turgidum var. durum) genotypes were used in this study. Experiment 2 was conducted at Indian Head for 3 years.
                  Folicur 3.6F was applied from stem elongation to early milk stage for a durum cultivar. The incidence of black point
                  was very low at Swift Current. Severe black point incidence occurred at Indian Head in 1999, which could be related
                  to low temperature and high rainfall during the grain filling stage. Durum wheat cultivars had higher black point
                  incidence than the common wheat cultivars. Fungicide applications from stem elongation to flag emergence could
                  increase black point infection and it was, in many cases, associated with an increase in kernel mass. Fungicide
                  applications at or after head emergence could reduce the incidence of black point, although this was not consistent.
                  Key words: wheat, black point, fungicide, kernel mass.
                  Résumé : La présente étude fut entreprise afin de déterminer l’effet de fongicides sur la fréquence de la mélanose dans
                  le blé (Triticum spp.) du sud de la Saskatchewan, Canada. L’expérience 1 fut menée à Swift Current et à Indian Head
                  durant 3 ans. Du Folicur 3.6F (tébuconazole) et du Bravo 500 (chlorothalonil) furent appliqués à différents stades de
                  croissance, de la montaison à l’épiaison. Trois génotypes de blé tendre de printemps (T. aestivum) et trois de blé dur
                  (T. turgidum var. durum) furent utilisés dans la présente étude. L’expérience 2 fut menée à Indian Head durant 3 ans.
                  Du Folicur 3.6F fut appliqué de la montaison au stade grain laiteux d’un cultivar de blé dur. La fréquence de la
                  mélanose fut très faible à Swift Current. Une fréquence élevée de mélanose fut observée à Indian Head en 1999, ce
                  qui pourrait être dû aux basses températures et aux pluies abondantes qui ont prévalu pendant le stade de remplissage
                  du grain. Les cultivars de blé dur avaient plus de mélanose que les cultivars de blé tendre. Des applications de
                  fongicides, de la montaison à l’émergence de la feuille étendard, pourraient faire augmenter la mélanose, phénomène
                  associé, dans plusieurs cas, à l’augmentation de la masse des grains. Des applications de fongicides à l’épiaison ou
                  après pourraient réduire la fréquence de la mélanose, quoique les résultats ne furent pas constants.

                  Mots clés : blé, mélanose, fongicide, masse des grains.


                                                                              293
Introduction                                                                         crease. al.: black point of wheat / foliar fungicides
                                                                            into the Wang et If the discoloration penetrates and extends
                                                                            throughout the endosperm, it is referred to as “penetrated
   Black point is common in all wheat growing regions of                    smudge”.
the world (Lorenz 1986). Black point is characterized by a
distinct dark brown or black discoloration of the whole                        Black point of wheat is often associated with the presence
germ and surrounding area. According to the Official Grain                  of Alternaria spp. and Cochliobolus sativus (Ito & Kurib.)
Grading Guide (Canadian Grain Commission 2001), the                         Drechsl. ex Dastur (anamorph Bipolaris sorokiniana (Sacc.
discoloration is considered “smudge” if more than one half                  in Sorok.) Shoem.), although many other organisms have
of the kernel is discolored, or if the discoloration extends                been isolated from affected grain (Conner and Kuzyk 1988a;
                                                                            Fernandez et al. 1994; King et al. 1981; Rees et al. 1984).
   Accepted 27 May 2002.                                                       For common wheat, the poor appearance of wheat with
                                                                            black point damage limits marketing to end users. Discolor-
   H. Wang,1 M.R. Fernandez, F.R. Clarke, R.M. DePauw,                      ation of germ and bran associated with this kernel infection
   and J.M. Clarke. Semiarid Prairie Agricultural Research                  is also a detriment to production of germ and breakfast ce-
   Centre, Agriculture and Agri-Food Canada, P.O. Box 1030,
                                                                            reals (Dexter and Edwards 1997). For durum wheat, black
   Swift Current, SK S9H 3X2, Canada.
                                                                            point incidence has little effect on semolina milling yield,
   1
       Corresponding author (e-mail: wangh@agr.gc.ca).                      spaghetti color, or cooking quality, although an increase in

Can. J. Plant Pathol. 24: 287–293 (2002)
288                                                                                      Can. J. Plant Pathol. Vol. 24, 2002


specks causes aesthetic defects in pasta (Dexter and Matsuo     Materials and methods
1982; Dexter and Edwards 1998).
   Black point discoloration causes loss of grade. In Can-      Experiment 1
ada, black point infected kernels with levels of 10 and 20%        A 3-year experiment was conducted in the Brown soil
for Canadian Western Red Spring common wheat (CWRS)             zone near Swift Current (Swinton silt loam, Orthic Brown
and 5 and 10% for Canadian Western Amber durum wheat            Chernozem; Campbell et al. 1993a) and in the Black soil
(CWAD) are allowed for grade Nos. 1 and 2, respectively.        zone near Indian Head (Heavy clay, Black Chernozem;
Downgrading thresholds for kernels with smudge and pene-        Campbell et al. 1993b) from 1997 to 1999. A factorial, ran-
trated smudge damage are much lower than black point in-        domized complete block design was used. The first factor
fected kernels (Canadian Grain Commission 2001). In the         was genotypes, consisting of three CWRS cultivars (AC
United States, only 2 and 4% black point infected kernels       Domain, Laura, and AC Elsa), two durum cultivars, (Kyle
are permitted for grade Nos. 1 and 2, respectively, for all     and Durex), and an unregistered durum wheat genotype
classes of wheat, except mixed wheat (USDA 1993). In            (DT 665). The second factor was fungicide applications. In
Australia, 5 and 3% of black point and other stained grains     1997, there were four fungicide treatments: a nonfungicide
are permitted for grade No. 1 of Australian Prime hard          control, Folicur 3.6F (39% tebuconazole, a systemic fungi-
wheat and Australian durum wheat, respectively (Australian      cide) applied at stem elongation (early application, Zadoks’
Wheat Board 2000).                                              growth stage, GS 31–32; Zadoks et al. 1974), at head emer-
   Seed is susceptible to infection during filling or matura-   gence (late application, GS 58), and at both stages (dual ap-
tion, particularly at the milk and soft dough stages (Conner    plication). A registered fungicide for the control of leaf
1988). Irrigation or heavy rainfall (Conner 1988), low tem-     spotting diseases in wheat in Canada, Bravo 500 (500 g·L–1
perature, and frosts during kernel development (Fernandez       of chlorothalonil, a contact, protectant fungicide), was
et al. 2000) could increase black point incidence. Conner et    added in 1998 and 1999. There were seven fungicide treat-
al. (1992) reported that high nitrogen application rates in-    ments: a nonfungicide control, Folicur 3.6F sprayed at flag
creased black point incidence in soft white spring wheat.       leaf just visible (early application, GS 37), at head emer-
There are some differences in susceptibility to black point     gence (late application), and at both stages (dual applica-
infection among wheat varieties (Conner and Davidson            tion); Bravo 500 sprayed as the flag leaf ligule just became
1988; Fernandez et al. 2000). Gooding et al. (1993) indi-       visible (early application), at head emergence (late applica-
cated that kernel size could be related to the incidence of     tion), and at both stages (dual application). Folicur and
black point. Ellis et al. (1996) found that some cultivars      Bravo were sprayed at the rate of 336 and 2500 mL·ha–1 of
with larger kernels had higher incidence of black point than    product, respectively, using a water volume of 900 L·ha–1
cultivars with smaller kernels. Lorenz (1986) showed that       for each application. A hand-held compressed-air sprayer
heavier grains were most commonly affected by black point       with an adjustable cone spray pattern tip was used. The
within a grain sample. For triticale, Khetarpal and Agarwal     spray tip was set to give a 75° cone pattern and a medium
(1979) also observed that kernel mass of black point af-        spray droplet size (approximately 250–500 µm). A pre-
fected kernels was significantly higher than that of healthy    mixed amount of spray solution was added to the sprayer,
kernels.                                                        and the tank was repressurized, before spraying each plot.
   Few studies have been done on the impact of fungicide        Each plot was sprayed entirely with care being taken to en-
application on the incidence of black point and results dif-    sure full and even coverage. Plots were grown on wheat
fered. Conner and Kuzyk (1988b) observed that both              summer fallow with four replications. Seeding rates were
triadimenol and triadimefon applied at the end of flowering     250 seeds/m2, which were adjusted according to a germina-
reduced black point incidence for one of two soft white         tion test done prior to seeding. Each plot consisted of 16
spring wheat cultivars. Gooding et al. (1993) found that        rows, 3 m long and spaced 0.23 m apart, with a 1-m-wide
both prochloraz and fenpropimorph applied at flag leaf and      buffer area seeded to faba bean (Vicia faba L.) between
head emergence increased black point incidence in some          plots. Seeding dates were 14 May and 23 May 1997, 12
common wheat cultivars. Ellis et al. (1996) indicated that      May and 26 May 1998, and 26 May and 30 May 1999 at
fungicide applications leading to large increase in kernel      Swift Current and Indian Head, respectively.
mass could increase black point infection. It is widely re-
ported that fungicide applications increase kernel mass         Experiment 2
(Morris et al. 1989; Gooding et al. 1994; McCabe and               At Indian Head from 1997 to 1999, Folicur 3.6F was
Gallagher 1993; Entz et al. 1990).                              used on the CWAD cultivar Kyle in four treatments: a
   In the past decade, there has been an increase in the in-    nonfungicide control; applications at stem elongation and
cidence of leaf spotting diseases and fusarium head blight      head emergence; one application alone at early milk stage
of wheat in southern Saskatchewan, Canada (Fernandez et         (GS 73); and applications at stem elongation, head emer-
al. 1997; Fernandez et al. 2001b). Consequently, there is       gence, and early milk stage. The application rate was
increased pressure on producers to chemically control           336 mL·ha–1 of product with a XR Teejet 8002VS plot
wheat diseases. However, the effect of fungicide applica-       sprayer at 80° angles and a pressure of 276 kPa. Plants were
tion on kernel discoloration in this area is not known. This    grown on wheat summer fallow in 1997 and 1999 and on
study was undertaken to determine the effect of fungicides      wheat stubble in 1998. There were four replications for
and application timing on the incidence of black point          each treatment in a randomized complete block design. Plot
of common and durum wheat genotypes in southern                 size was 9 × 11 m (15 × 16 m in 1997) with 8-m-wide (1-m
Saskatchewan.                                                   in 1997) buffer areas seeded to barley on each side of the
Wang et al.: black point of wheat / foliar fungicides                                                                              289

Table 1. Mean monthly air temperature and precipitation (May–August) at Swift Current and Indian Head, Sask.
                                           Temperature (°C)                                 Precipitation (mm)
                                           1997         1998      1999       1920–1999      1997      1998       1999      1920–1999
Swift Current
May                                        10.2         12.6       9.9       10.9            50.3      38.1       93.9      39.4
June                                       16.3         14.0      14.2       15.3            69.8      90.1       86.4      71.9
July                                       18.1         20.1      16.4       18.6            43.6      37.0       60.3      48.2
August                                     18.7         20.9      18.9       17.6            48.0      35.3       16.8      41.6
Mean temperature or total precipitation    15.8         16.9      14.9       15.6           211.7     200.5      257.4     201.2
Indian Head
May                                         9.6         11.2      10.5       10.8            12.7      49.3       88.5      44.9
June                                       17.4         13.0      14.5       15.6            43.6     174.6      114.6      78.0
July                                       18.2         18.2      16.0       18.7            17.9      22.8       74.6      58.7
August                                     17.6         19.3      16.6       17.5            40.0      39.2       68.2      50.6
Mean temperature or total precipitation    15.7         15.4      14.4       15.6           114.2     285.9      345.9     232.1


plots. Row spacing and seeding rate were the same as ex-                 ing the whole growing season in 1997. In 1998 and 1999,
periment 1. Seeding dates were 23 May 1997, 22 May                       precipitation was above normal, but in 1999, temperature
1998, and 29 May 1999.                                                   was low during the whole growing season and caused a de-
   Grain yields were determined by harvesting plots. The in-             lay in maturity and frost damage to the kernels. The effect
cidence of black point was determined in a sample of 1000                of fungicide treatments on yield was not significant or rela-
kernels (300 in 1997) randomly taken from the harvested                  tively small (Wang et al. 2002).
grain from each plot. Smudge and penetrated smudge damaged
kernels were also counted. Kernel mass was determined on                 Swift Current
a sample of 1000 kernels randomly taken from the har-                      The incidence of black point at Swift Current was very
vested grain. Daily maximum and minimum air temperature                  low. On average, it was less than 1% each year. The highest
and precipitation were recorded for the growing season at a              black point incidence observed was only 3%, which was
weather site located 100–200 m from the test at each loca-               Durex in the nonfungicide control in 1997. Neither smudge
tion. Long-term (1920–1999) weather records were also                    nor penetrated smudge damaged kernels were observed. Be-
collected from those weather sites (Agriculture and Agri-                cause the incidence of black point at Swift Current was too
Food Canada, unpublished data).                                          low to be of practical importance, results from the Swift
   All dependent variables were analyzed using the mixed                 Current experiment were not presented.
model (SAS Institute Inc. 1996) with the REML (restricted
maximum likelihood) option for each location within each                 Indian Head
year with genotypes and (or) fungicide treatments fixed and
replications random. Treatments and genotypes were com-                  1997 — Smudge infected kernels were very few in number
pared with Fisher’s protected least significant differences              and no penetrated smudge damaged kernels were found at
(LSD) based on Student’s t distribution. For experiment 1,               Indian Head in 1997 (data not shown). The genotype effect
the ESTIMATE statement in the PROC MIXED procedure                       (P < 0.001) and fungicide treatment effect (P < 0.01) on
was used to compare durum and CWRS cultivars and early                   black point incidence was significant, but the genotype ×
(at stem elongation in 1997 and at flag emergence in 1998                treatment interaction was not significant (Table 2). Durum
and 1999) and late applications (at head emergence and                   genotypes, especially Durex, had significantly more black
dual applications). If the genotype × treatment interaction              point infected kernels than CWRS cultivars, which were as-
was significant, treatment comparisons were done for each                sociated with heavier kernels (Table 3). Early Folicur appli-
cultivar. “Significance” in the text refers to P < 0.05, if the          cation alone (at stem elongation) tended to have more black
P value is not given.                                                    point infected kernels than treatments including a late fun-
                                                                         gicide application (at head emergence and dual application).
                                                                         Although this increase was small in number for most of the
Results                                                                  cultivars, it was sufficient to result in downgrading for Du-
                                                                         rex and DT 665 according to the Canadian standard for
Experiment 1                                                             CWAD wheat (Canadian Grain Commission 2001). On av-
   Comparisons in long-term (1920–1999) weather data                     erage, black point incidences were 8 and 4% for late and
showed that mean air temperature during the growing sea-                 dual treatments and 11 and 6% for early treatments, for Du-
son (May to August) at Swift Current was similar to those                rex and DT 665, respectively. No fungicidal effect on kernel
at Indian Head, but precipitation at Swift Current was lower             mass was observed.
than Indian Head (Table 1). In general, temperatures were
normal during the 3 years of the study, while precipitation              1998 — Similar to 1997, there were very few kernels with
was higher than average during the early season (May and                 smudge damage and no kernels with penetrated smudge
June) and was normal during the late season (July and Au-                damage at Indian Head in 1998 (data not shown). The geno-
gust) at Swift Current. At Indian Head, it was very dry dur-             type difference, fungicide treatment effect and genotype ×
290                                                                                                     Can. J. Plant Pathol. Vol. 24, 2002

Table 2. Probabilities for the effects of genotype, treatment, and     Table 3. Black point incidence (%) and thousand kernel mass
genotype × treatment interaction on the incidence of black point       (g) at Indian Head in 1997 in experiment 1.
(%), smudge (%), and penetrated smudge (%) and thousand
kernel mass (g) in 1997, 1998, and 1999 at Indian Head in                                                              Black       Thousand
experiment 1.                                                                                                          point       kernel mass
                                                                       Cultivar
                   Black                    Penetrated   Thousand      DT 665                                          5.6         44.9
                   point       Smudge       smudge       kernel mass   Durex                                           9.8         48.5
1997                                                                   Kyle                                            6.3         42.6
Genotype (G)       ***         0.58         —            ***           AC Domain                                       1.4         32.5
Treatment (T)      **          0.42         —            0.24          AC Elsa                                         1.0         32.9
G×T                0.23        0.46         —            0.46          Laura                                           1.8         32.6
1998                                                                   Mean                                            4.3         39.0
G                  ***         0.43         —            ***           LSD (0.05)                                      1.0          0.9
T                  ***         0.45         —            **            Contrast: Durum vs. CWRS                        5.8***      12.7***
G×T                ***         0.48         —            **            Treatment
1999                                                                   Nonfungicide control                            4.8         38.5
G                  ***         ***          ***          ***           Folicur at stem elongation (early)              4.9         39.0
T                  0.25        0.70         0.66         **            Folicur at head emergence (late)                3.4         39.3
G×T                0.89        0.74         0.84         0.97          Folicur at stem elongation + head               4.2         38.9
  **Significant at 0.01 level of probability.                            emergence (dual)
  *** Significant at the 0.001 level of probability.                   LSD (0.05)                                      0.8         ns†
                                                                       Contrast: early vs. late and dual               1.1**       –0.1ns
                                                                         **Significant at the 0.01 level of probability.
                                                                         ***Significant at the 0.001 level of probability.
treatment interaction were significant on both black point               †
                                                                           ns, not significant at the 0.05 level of probability.
infection and kernel mass (Table 2). In general, durum
genotypes had higher incidence of black point and heavier
kernels than CWRS cultivars (Table 4). For both fungi-
cides, early application (at flag emergence) significantly in-         Experiment 2
creased black point infected kernels for all durum                        The effect of fungicide treatments on yield was not sig-
genotypes compared to nonfungicide controls and resulted               nificant in each year (data not shown). Incidences of black
in downgrading according to the Canadian standard for                  point, smudge, and penetrated smudge of the nonfungicide
CWAD wheat (Canadian Grain Commission 2001). Effects                   control were similar to that in experiment 1 at Indian Head
of early fungicide applications were not consistent for                each year. The effect of Folicur treatments on the incidence
CWRS cultivars, although black point incidence increased               of black point was significant at the level of P < 0.10 in
in most cases. Similar to 1997, treatments including a late            each year (Table 6). In 1997, treatments including an appli-
fungicide application (at head emergence and dual applica-             cation at the early milk stage reduced black point incidence
tions) tended to have lower incidence of black point com-              (P < 0.10). In 1998 and 1999, fungicide applications at and
pared with early applications (at flag emergence) for all              before head emergence tended to increase both black point
cultivars and the difference was significant for four geno-            incidence and kernel mass (P < 0.10). Although treatment
types (DT665, Durex, AC Domain, and Laura). Treatment                  differences in the incidence of black point were at a low
effects on the incidence of black point were not sufficient to         level of significance (P < 0.10), the difference in number
result in downgrading or upgrading for CWRS cultivars.                 was high and downgrading or upgrading effects occurred in
For durum wheat, the increase in the incidence of black                each year. Similar to experiment 1, Folicur applications had
point by any fungicide treatment was always associated                 no significant effect on incidences of smudge or penetrated
with an increase in kernel weight. Treatments of late and              smudge damage (data not shown).
dual Bravo applications tended to have lower black point
incidence and lower kernel weight for Durex and DT 665                 Discussion
compared with other fungicide treatments.
                                                                          The environment had a major impact on the incidence of
1999 — At Indian Head in 1999, the incidence of black                  black point. Swift Current always had less black point inci-
point was very high, and kernels with smudge and pene-                 dence than Indian Head. Low temperature and high rainfall
trated smudge damage were observed (Table 5). This could               during the period of grain filling resulted in severe kernel
be associated with low temperature and high rainfall during            discoloration.
grain filling and frost damage before maturity (Fernandez et              Durum wheat genotypes consistently had more black
al. 2000). Similar to 1997 and 1998, durum genotypes had               point kernels than the common wheat cultivars. Fernandez
higher incidence of kernel discoloration and heavier kernels           et al. (2001a) indicated that the high black point incidence
than CWRS cultivars (P < 0.001) (Table 2). Treatment ef-               in durum genotypes could be related to their white seed
fects were not significant on kernel diseases but significant          color. It might be also related to their heavier kernels com-
on kernel mass (P < 0.01). Fungicide applications at flag              pared with CWRS cultivars. Gooding et al. (1993) and Ellis
emergence tended to increase kernel mass.                              et al. (1996) found a positive relationship between black
Wang et al.: black point of wheat / foliar fungicides                                                                                     291

Table 4. Black point incidence (%) and thousand kernel mass (g) at Indian Head in 1998 in experiment 1.
                                                                       DT 665   Durex           Kyle         AC Domain   AC Elsa       Laura
Black point
Nonfungicide control                                                    5.6      8.4              3.9         4.8         1.3           6.6
Folicur at flag emergence (early)                                       8.3     24.3              6.6         5.5         3.5           7.0
Folicur at head emergence (late)                                        7.0     10.1              4.8         2.5         2.0           3.7
Folicur at flag emergence + head emergence (dual)                       5.0      9.3              5.5         3.4         2.1           3.3
Bravo at flag emergence (early)                                         7.7     13.1              6.1         3.4         2.0           9.6
Bravo at head emergence (late)                                          4.2      5.6              4.5         2.6         1.2           5.0
Bravo at flag emergence + head emergence (dual)                         4.8      4.9              5.9         2.3         2.0           5.2
Mean                                                                    6.1     10.8              5.3         3.5         2.0           5.8
Treatment LSD (0.05)                                                    1.0
Cultivar LSD (0.05)                                                     0.9
Contrast: early vs. late and dual                                       2.8**   11.2***           1.2ns†      1.8***      0.9ns         4.0***
Kernel mass
Nonfungicide control                                                   43.3     40.4            39.4         31.3        30.0          31.5
Folicur at flag emergence (early)                                      44.6     44.0            43.2         31.9        33.4          31.3
Folicur at head emergence (late)                                       45.2     44.9            41.8         31.3        32.5          32.0
Folicur at flag emergence + head emergence (dual)                      44.0     45.5            42.6         31.7        32.6          31.8
Bravo at flag emergence (early)                                        44.0     43.0            43.0         33.9        31.6          31.5
Bravo at head emergence (late)                                         41.8     40.1            38.6         30.5        31.4          31.1
Bravo at flag emergence + head emergence (dual)                        41.4     39.7            41.0         30.6        32.1          30.7
Mean                                                                   43.5     42.5            41.4         31.6        31.9          31.4
Treatment LSD (0.05)                                                    0.9
Cultivar LSD (0.05)                                                     0.8
Contrast: early vs. late and dual                                       1.2*     1.0ns            2.1**       1.9*        0.4ns        0.0ns
  *Significant at the 0.05 level of probability.
  ** Significant at the 0.01 level of probability.
  ***Significant at the 0.001 level of probability.
  †
    ns, not significant at the 0.05 level of probability.

           Table 5. Black point (%), smudge (%), and penetrated smudge (%) incidence and thousand kernel mass (g) at
           Indian Head in 1999 in experiment 1.
                                                                                                           Penetrated    Thousand
                                                                 Black point           Smudge              smudge        kernel mass
           Cultivar
           DT 665                                                11.5                    4.8                0.8          34.8
           Durex                                                 10.3                    3.8                0.7          34.1
           Kyle                                                  12.9                    3.1                0.6          31.6
           AC Domain                                              5.6                    1.6                0.1          28.5
           AC Elsa                                                6.6                    3.9                0.6          30.0
           Laura                                                  9.7                    3.0                1.1          25.8
           Mean                                                   9.4                    3.4                0.7          30.8
           LSD (0.05)                                             2.2                    1.0                0.3           0.8
           Contrast: durum vs. CWRS                               4.3***                 1.1***             0.1ns†        5.4***
           Treatment
           Nonfungicide control                                   8.3                    3.0                0.6          30.0
           Folicur at flag emergence (early)                      9.6                    3.3                0.7          31.1
           Folicur at head emergence (late)                       9.8                    3.6                0.7          30.7
           Folicur at flag emergence + head                      11.1                    3.7                0.8          31.6
             emergence (dual)
           Bravo at flag emergence (early)                         8.2                   3.0                0.5          31.1
           Bravo at head emergence (late)                          9.3                   3.4                0.6          30.3
           Bravo at flag emergence + head                          9.7                   3.5                0.6          30.9
             emergence (dual)
           LSD (0.05)                                             ns                    ns                  ns            0.9
           Contrast: early vs. late and dual                     –1.1ns                –0.4ns              –0.1ns         0.2ns
             ***Significant at the 0.001 level of probability.
             †
               ns, not significant at the 0.05 level of probability.
292                                                                                                       Can. J. Plant Pathol. Vol. 24, 2002

Table 6. Black point incidence (%) and thousand kernel mass                 Campbell, C.A., Curtin, D., Brandt, S.A., and Zentner, R.P. 1993a.
(g) of Kyle at Indian Head in experiment 2.                                    Soil aggregation as influenced by cultural practices in Sas-
                                                                               katchewan. II. Brown and Dark Brown Chernozemic soils. Can.
                                                  1997        1998   1999      J. Soil Sci. 73: 597–612.
Black point                                                                 Campbell, C.A., Moulin, A.P., Curtin, D., Lafond, G.P., and
Nonfungicide control                                7.1        6.9   16.1      Townley-Smith, L. 1993b. Soil aggregation as influenced by
Folicur at stem elongation         + head           5.7       11.4   24.5      cultural practices in Saskatchewan: I. Black Chernozemic soils.
  emergence                                                                    Can. J. Soil Sci. 73: 579–595.
Folicur at early milk                               3.6        6.7   12.3   Canadian Grain Commission. 2001. Official grain grading guide.
Folicur at stem elongation         + head           4.0        4.6   16.1      Vol. 4. Wheat. Canadian Grain Commission, Winnipeg, Man.
                                                                               pp. 1–61.
  emergence + early milk
                                                                            Conner, R.L. 1988. Influence of irrigation timing on black point
Mean                                                5.1        7.4   17.3
                                                                               incidence in soft white spring wheat. Can. J. Plant Pathol. 9:
Treatment LSD (0.10)                                2.4        4.3    8.0
                                                                               301–306.
Thousand kernel mass                                                        Conner, R.L., and Davidson, J.G.N. 1988. Resistance in wheat to
Non-fungicide control                             40.8        37.9   34.3      black point caused by Alternaria alternata and Cochliobolus
Folicur at stem elongation         + head         41.6        40.5   37.6      sativus. Can. J. Plant Sci. 68: 351–359.
  emergence                                                                 Conner, R.L., and Kuzyk, A.D. 1988a. Black point incidence in
Folicur at early milk                             42.0        39.8   32.9      soft white spring wheat in southern Alberta and Saskatchewan
Folicur at stem elongation         + head         40.1        39.4   34.9      between 1982 and 1987. Can. Plant Dis. Surv. 68: 27–31.
  emergence + early milk                                                    Conner, R.L., and Kuzyk, A.D. 1988b. Effectiveness of fungicides
Mean                                              41.1        39.4   34.9      in controlling stripe rust, leaf rust, and black point in soft white
Treatment LSD (0.10)                              ns†          1.7    3.0      spring wheat. Can. J. Plant Pathol. 10: 321–326.
  †
      ns, not significant at the 0.05 level of probability.                 Conner, R.L., Carefoot, J.M., Bole, J.M., and Kozub, G.C. 1992.
                                                                               The effect of nitrogen fertilizer and irrigation on black point in-
                                                                               cidence in soft white spring wheat. Plant Soil, 140: 41–47.
point incidence and kernel mass among some wheat                            Dexter, J.E., and Edwards, N.M. 1997. The Implications of Fre-
cultivars (Triticum aestivum L.).                                              quently Encountered Grading Factors on the Processing Quality
   The association between increased kernel mass and in-                       of Common Wheat. The 101st Association of Operative Millers
creased black point incidence caused by fungicide applica-                     Trade Show, 1997, Nashville, Tenn. Grain Research Laboratory,
tions was found by other studies (Ellis et al. 1996). Ellis et                 Canadian Grain Commission, Winnipeg, Man. Contrib. M212.
al. (1996) indicated that a larger and wider kernel caused by               Dexter, J.E., and Edwards, N.M. 1998. The Implications of Fre-
fungicide application could lead to a more open floret al-                     quently Encountered Grading Factors on the Processing Quality
lowing greater access to the germ end of the grain and,                        of Durum Wheat. The 102nd Association of Operative Millers
therefore, providing a greater opportunity for kernel infec-                   Trade Show, 1998, Phoenix, Ariz. Grain Research Laboratory,
tion. Producers, who are using fungicides to control leaf                      Canadian Grain Commission, Winnipeg, Man. Contrib. M231.
diseases, should be aware of the possible risk of increasing                Dexter, J.E., and Matsuo, R.R. 1982. Effect of smudge and black
the incidence of black point.                                                  point, mildewed kernels, and ergot on durum wheat quality. Ce-
                                                                               real Chem. 59: 63–69.
   Some fungicide applications at or after head emergence,
                                                                            Ellis, S.A., Gooding, M.J., and Thompson, A.J. 1996. Factors in-
especially for Bravo, inhibited the development of black
                                                                               fluencing the relative susceptibility of wheat cultivars (Triticum
point disease. Similar results were observed by Conner and                     aestivum L.) to black point. Crop Prot. 15: 69–76.
Kuzyk (1988b). Ellis et al. (1996) suggested the use of late                Entz, M.H., Van Den Berg, C.G.J., Lafond, G.P., Stobbe, E.H.,
fungicide applications targeted at the head to control black                   Rossnagel, B.G., and Austenson, H.M. 1990. Effect of late-
point infection. Late fungicide applications aimed at con-                     season fungicide application on grain yield and seed size distri-
trolling diseases, such as fusarium head blight, may be ben-                   bution in wheat and barley. Can. J. Plant Sci. 70: 699–706.
eficial to reducing the incidence of black point.                           Fernandez, M.R., Clarke, J.M., DePauw, R.M., Irvine, R.B., and
   The significant genotype difference in susceptibility to                    Knox, R.E. 1994. Black point and red smudge in irrigated
black point infection indicated that selecting cultivars resis-                durum wheat in southern Saskatchewan in 1990–1992. Can. J.
tant to kernel discoloration would be an efficient measure to                  Plant Pathol. 16: 221–227.
control this disease.                                                       Fernandez, M.R., DePauw, R.M., Clarke, J.M., Zentner, R.P., and
                                                                               McConkey, B.G., 1997. Tan spot in Western Canada. In Pro-
Acknowledgements                                                               ceedings of the International Helminthosporium Workshop, 9–
                                                                               14 Feb. 1997. Edited by E. Duveiller, H.J. Dubin, J. Reeves,
  This work was supported by a Western Grains Research                         and A. McNab. CIMMYT, Mexico. pp. 73–79.
Foundation grant and the Agriculture and Agri-Food Can-                     Fernandez, M.R., Clarke, J.M., and DePauw, R.M. 2000. Black
ada Matching Investment Initiative. Technical assistance by                    point reaction of durum and common wheat cultivars grown un-
D. Kern, Y. Chen, D. Green, and O. Thompson is greatly                         der irrigation in southern Saskatchewan. Plant Dis. 84: 892–894.
appreciated.                                                                Fernandez, M.R., DePauw, R.M., and Clarke, J.M. 2001a. Reac-
                                                                               tion of common and durum wheat cultivars to infection of ker-
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