287 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: firstname.lastname@example.org). 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. 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