The control of dry bean anthracnose through seed treatment and the correct application timing of foliar fungicides

Crop Protection 37 (2012) 81e90

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The control of dry bean anthracnose through seed treatment and the correct application timing of foliar fungicides C.L. Gillard a, N.K. Ranatunga a, *, R.L. Conner b a b

University of Guelph Ridgetown Campus, 120 Main Street, Ridgetown, ON, Canada N0P 2C0 Morden Research Station, Agriculture and Agri-Food Canada, Morden, MB, Canada R6M 1Y5

a r t i c l e i n f o

a b s t r a c t

Article history: Received 15 July 2011 Received in revised form 15 February 2012 Accepted 20 February 2012

In 2005 and 2006, a study was carried out to control anthracnose of dry bean (Phaseolus vulgaris L.), caused by Colletotrichum lindemuthianum, using DCT (diazinon þ captan þ thiophanate-methyl) and Apron Maxx (metalaxyl-m þ fludioxonil) seed treatments and the foliar application of pyraclostrobin and azoxystrobin fungicides under low and high disease pressure at Exeter, ON and Morden, MB. Four single fungicide application timings at the 5th trifoliolate (A), 1st flower (B), full flower (C) and 10 days after full flower (D) were compared to three sequential application timings (A þ C, B þ C and B þ D). The experimental setup was a randomized complete block design with four replicates. Data on disease ratings for leaf veins and pods, plant maturity, dockage, pick, seed weight, yield and return on investment (ROI) were collected. For seed treatments, DCT provided superior disease control on leaf and pod tissue under low and high disease pressure. The combined effect of seed treatments and foliar spray timings improved plant health, extended crop maturity and increased yield over seed treatments alone. The sequential fungicide treatments were superior to the single fungicide treatments in most environments. Under moderate to severe disease pressure, two fungicide applications and a seed treatment are required to maximize economic returns for the grower. Ó 2012 Elsevier Ltd. All rights reserved.

Keywords: Anthracnose Colletotrichum lindemuthianum Phaseolus vulgaris Fungicides Seed treatment Timing

1. Introduction Dry bean (Phaseolus vulgaris L.) is vulnerable to anthracnose Colletotrichum lindemuthianum (Sacc. & Magnus) Briosi & Cavara disease in Canada, as well as in many other bean producing areas in the world. The disease can cause complete yield losses for susceptible bean cultivars when severely infected seed is planted under favourable weather conditions (Pastor-Corrales and Tu, 1989). Disease spread from an infected plant is limited by the distance of splashing rain drops. Therefore, the spread of the disease from field to field is largely due to the planting of infected seeds (Tu, 1981). Planting of disease free seed produced under strictly controlled conditions is an effective strategy to control bean anthracnose and has been adopted in various bean crop production regions (Tu, 1988; Pastor-Corrales and Tu, 1989). The emergence rates of infected seedlings is cultivar dependant (Conner et al., 2006, 2009) and can result in the rapid spread of the disease from infected seedlings early in the growing season (Conner et al., * Corresponding author. Tel.: þ1 (0) 112266639402. E-mail addresses: [email protected], [email protected] (N.K. Ranatunga). 0261-2194/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2012.02.009

2006). Disease severity rises as the rate of seed-borne infection (Conner et al., 2009) and the lesion size in the infected seed increases (Tu, 1983). Fungicide seed treatment is widely used to manage seed-borne infections. Its benefits are most clearly seen under environmental conditions that are favourable for the disease development (Bradley, 2008). Seed treatments are effective in controlling anthracnose on seed with slight or moderately sized anthracnose lesions, but are less effective on more severe infections (Tu, 1988). In soybean, seed treated with metalaxyl þ azoxystrobin or fludioxonil þ mefenoxam had increased plant establishment and yield in the presence of a wide range of soil-borne diseases (Bradley, 2008). Until recently, DCT (diazinon 6% þ captan 18% þ thiophanate-methyl 14% w/w) has been the most commonly used registered seed treatment compound in Canada for bean anthracnose control, since thiophanate-methyl is effective against the disease (Tu, 1996). Genetic resistance has been successfully utilized to control anthracnose, but the high levels of pathogenic variation within C. lindemuthianum have hindered the use of resistant varieties in many bean producing countries (Pastor and Tu, 1989). Planting disease free seed (Dillard and Cobb, 1993), along with a 2e3 year crop rotation with non-host crops to reduce inoculum level from

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infested debris (Dillard and Cobb, 1993; Schwartz et al., 2005), the use of resistant cultivars (Ntahimpera et al., 1996) and fungicide seed treatments (Trutmann et al., 1992) are all proven strategies for controlling bean anthracnose. In Ontario, growers have historically managed dry bean anthracnose with seed treatments (Tu, 1988). More recently, seed treatments were combined with a foliar fungicide (Pynenburg et al., 2011) to provide more season-long disease control. A sequential application of foliar fungicides, with the time of application based on crop and disease development stages, is an effective strategy for dry bean anthracnose management, improving yields, seed quality and economic returns (Conner et al., 2004; Gillard et al., 2012). However, even the best sequential fungicide application allows for a significant amount of disease development, under certain environmental conditions. Growers require an integrated approach to the chemical control of anthracnose in dry beans, in order to maintain a successful disease management program. The development of an integrated approach for controlling bean anthracnose using seed treatments and foliar fungicides, with the timing of fungicide application based on disease development stages, has not been reported in the literature. Therefore, this study was conducted to determine the combined effects of two seed treatments and various application timings of two foliar fungicides on anthracnose levels, seed yield, seed quality and economic returns-on dry bean under two levels of disease pressure. 2. Materials and methods 2.1. Experimental sites and seed preparation A series of experiments were carried out in Canada at two locations in Exeter, ON and one location in Morden, MB in 2005 and 2006. Mixtures of seed with and without visible anthracnose lesions were used to modify the anthracnose pressure in order to create low and high disease pressure in separate experiments, as the presence of visible anthracnose lesions on seed usually leads to an increase in disease pressure (Conner et al., 2006). The seed was obtained from previous studies, and was sorted using a Sortex electric eye (model 425BF, Gunson Sortex Ltd., London, England) into unblemished (no lesions) and blemished (with lesions) lots. The susceptible navy bean cultivar Aspen was used at the Exeter location in 2005, but it was replaced with the susceptible navy bean cultivar AC Kippen in 2006, due to seed supply issues. For the Morden location, the susceptible pinto bean cultivar AC Pintoba was used in both years. Low infection experiments (E1, E3 and M1) used 100% unblemished seed, while a mixture of 50% unblemished and 50% blemished seed was used for the high infection experiments (E2, E4 and M2). The experiments E1 and E2 were planted in 2005, and E3, E4, M1 and M2 were planted in 2006. 2.2. Treatments The two seed treatments evaluated were Apron Maxx RTA (metalaxyl-m þ fludioxonil, 3.8 þ 2.5 g ai ha1) from Syngenta Crop Protection Canada Inc., Guelph, ON and DCT (diazinon þ captan þ thiophanate-methyl, 6% þ 18% þ 14% w/w, 197.6 g ai ha1) from Norac Concepts Inc., Guelph, ON. The seed treatments were combined with seven application timings of two strobilurin class fungicides; pyraclostrobin (BASF Canada Inc., Mississauga, ON) and azoxystrobin (Syngenta Crop Protection Canada Inc., Guelph, ON). Pyraclostrobin and azoxystrobin were evaluated in separate experiments at the Exeter location at the rate of 100 and 125 g ai ha1 respectively, while pyraclostrobin alone was evaluated at the Morden location. Pyraclostrobin is considered nonsystemic, while azoxystrobin is considered xylem systemic

(Bartlett et al., 2002). Fungicide application timing included four single timings at 5th trifoliolate (A), 1st flower (B), full flower (C) and 10 days after full flower (D) and three sequential timings at A þ C, B þ C and B þ D. Treatments were compared to three controls (Table 1). The non-infected sprayed (NIS) control had pyraclostrobin or azoxystrobin applied every two weeks, respective to the fungicide experiment, starting at the A timing of fungicide application. Infected control (IC) and non-infected control (NIC) were not sprayed with any fungicide. The two non-infected controls used certified seed of the same cultivar. 2.3. The experimental design and field lay out The experimental design of all of the experiments was a randomized complete block design (RCBD) with 17 treatments (two seed treatments  seven timings of fungicide applications and three controls) and 4 replications (Table 1). The Exeter experimental units consisted of 3 rows 6.0 m long and spaced 0.43 m apart. After emergence, the rows were trimmed to a 5 m length. One border row was seeded on each side with soybean, to reduce the spread of disease from plot to plot. The seeding rates were 22 and 19 seeds m1 for the white beans and soybeans, respectively. A five-row cone-seeder with John Deere Max Emerge planter units was used for seeding the trial. In the Morden experiments, each experimental unit consisted of 4 rows spaced 0.3 m apart and 5.4 m in length, which was later trimmed to 5.0 m. The seeding rate was 13.5 seeds m1. Four row soybean plots were planted between the bean plots and at the ends of the bean plots to reduce the spread of anthracnose between plots. A custom built four row plot planter, referred to as a “Cab Seeder” with double disk openers and 10 cm rubber wheel packers was used to seed the experiments. 2.4. Fungicide application At Exeter, fungicides were applied using a CO2 pressurized back pack sprayer with three 10-002 Billericay Air Bubble nozzles (Agratech, Rossendale, Lancashire, UK) spaced at 50 cm, with the spray solution applied at 346 kPa using 200 L ha1 water. At Morden, the fungicides were applied using a tractor mounted three point hitch sprayer equipped with Teejet 8004 XRT nozzles (Teejet Technologies, Wheaton, IL) spaced 50 cm apart, using 200 L ha1 of water at a pressure of 277 kPa. The dates of planting and fungicide applications for all the experiments are shown in Table 2. 2.5. Disease rating Ten plants from each plot were randomly selected and visually assessed for leaf vein and pod disease. Leaf vein ratings were conducted at 5th trifoliolate (6 week after planting (WAP)) and mid flower (9 WAP) stages by visually estimating the percentage of the Table 1 Treatments allocated for the anthracnose seed treatment and fungicide (pyraclostrobin and/or azoxystrobina) timing experiments in 2005 Exeter and 2006 Exeter and Morden. Seed treatment

Single sprayb timing

Sequential spray timingb

Control

1. Apron Maxx 2. DCT

1. A 2. B

1. A þ C 2. B þ C

3. C

3. B þ D

1. Infected Control (IC) 2. Non Infected Sprayed (NIS) 3. Non Infected Control (NIC)

4. D a

Azoxystrobin was used only at Exeter location. A e 5th trifoliolate stage, B e 1st flower stage, C e full flower stage and D e 10 days after full flower. b

C.L. Gillard et al. / Crop Protection 37 (2012) 81e90 Table 2 Crop stage and date of fungicide application for six experiments in 2005 and 2006. Year

2005

2006

Locationa e date of planting E1 e June 9 E2 e June 9 M1 e June 10 E3 e June 10 E4 e June 10 M2 e May 31

83

ROI ¼ ((Seed Yield  Dockage  2(Pick))*$0.46/kg)  Fungicide Cost  Fungicide Application Cost.

Crop stage and date of fungicide sprayedb A July July July July July July

21 21 14 14 14 14

B

C

D

Aug 3 Aug 3 Aug 3 July 22 July 22 Aug 3

Aug 6 Aug 6 Aug 8 July 28 July 28 Aug 8

Aug Aug Aug Aug Aug Aug

2.8. Statistical analysis 11 11 12 6 6 12

a A e 5th trifoliolate stage, B e 1st flower stage, C e full flower stage and D e 10 days after full flower. b E1, Exeter 2005 100% unblemished seed; E2, Exeter 2005 50% unblemished and 50% blemished seed; E3, Exeter 2006 100% unblemished seed; E4, Exeter 2006 50% unblemished and 50% blemished seed; M1, Morden 2006 100% unblemished seed; M2, Morden 2006 50% unblemished and 50% blemished seed.

leaf vein area on the underside of the leaves that was discoloured purple to black from disease symptoms. The percentage of the pod area that covered with anthracnose lesions was visually estimated at mid flower (9 WAP) and early pod formation (11 WAP) stages to determine the pod disease ratings. 2.6. Maturity and harvesting data Plant maturity was determined by the number of days from planting to 95% physiological maturity of the pods in an experimental unit. Harvesting was done using a small plot combine (Hege 140 Wintersteiger Inc., Salt Lake City, UT at Exeter and Wintersteiger Nurserymaster, Austria at Morden). The seed from each plot was weighed and the seed moisture content was measured using a Dickey-John GAC2100 moisture meter (Dickey-John, Auburn, IL). Then the seed was passed through a Clipper cleaner (Blount/Ferrell-Ross, Bluffton, IN) equipped with a 0.397 cm  1.905 cm screen and reweighed. Dockage was defined as any material or split/ undersized seed below the standard quality intermixed in a sample of seed (Canadian Grain Commission, 2011), and was estimated as the difference between the seed weight before and after cleaning, calculated as a percent. After the dockage was removed, pick was estimated as the percentage of seed which was discoloured by anthracnose in a random sample of 100 seeds. The dry bean industry uses a larger sample size (minimum 500 g) to determine pick, but this was not practical for this study.

An analysis of variance (ANOVA) was performed on the data using PROC MIXED (SAS version 9.1, SAS Institute Inc, Cary, NC). Fixed effects included seed treatment and fungicide application timing. Random effects included environment (location and/or different disease pressure experiments), rep (environment) and the interactions of environment with the fixed effects. In order to satisfy the assumptions for normality, based on the highest ShapiroeWilk statistic, an appropriate transformation was selected for each variable analyzed. The interaction of environment  seed treatment  fungicide spray treatment was used to determine if environments could be combined for analysis. Data was pooled into ‘groups’ when there was no significant interaction for environment  seed treatment  fungicide application timing. In order to satisfy the assumptions of normality, the raw data from each data ‘group’ was transformed, based on the highest ShapiroeWilk statistic. A log transformation was used for the disease severity values for the leaf veins at E2, E3 and E4 sites, on pod disease severity at all E sites at 9 WAP and on pick at M1 site of the pyraclostrobin experiment, and disease severity on leaf veins and pods at all E sites at 9 WAP, plant maturity at E1, E2 and E3 sites and dockage at all E sites of the azoxystrobin experiment. A square root transformation was used for the values for disease severity on leaf veins at E1 at 9 WAP, disease severity on pods at E3 site at 11 WAP, yield at E1 and E2 sites, dockage at all E sites, pick at E1 and M2 sites of the pyraclostrobin experiment and yield at E1 and E2 sites, seed weight at E1 and E2 sites and pick at E1 and E2 sites of the azoxystrobin experiment. An arcsine square root transformation was used for disease severity on the leaf veins at E3 and E4 sites at 6 WAP, disease severity on the pods at M1 and M2 sites and plant maturity at E1 and E2 sites of the pyraclostrobin experiment, and disease severity on leaf veins at E4 site at 6 WAP of the azoxystrobin experiment. Transformed means were back transformed to their original scale for presentation. Contrast treatment comparisons were carried out for the different treatment combinations. Significant differences between two means in a contrast were determined using the F-value. 3. Results

2.7. Yield assessment and return on investment (ROI) 3.1. Climatic conditions and disease pressure After seed cleaning to remove dockage, the gross yield for each plot was adjusted to standard storage moisture of 18% and converted to kg ha1. The marketable yield was calculated by subtracting the dockage and pick from the gross yield. Dockage was removed as a straight percentage. However, for pick, the percentage was doubled to allow for the loss of the poor quality seed and to account for the cost of removing such seed at the grain processing plant. The remaining marketable seed yield was multiplied by the market price of $0.46 kg1 to calculate a gross value ha1. Average crop insurance values from 2005 to 2006 were used to computing the market price (Agricorp, 2006). The ROI ($ ha1) was calculated by subtracting the costs for fungicides and fungicide application from the gross value ha1. The manufacturer average retail price in 2006 for pyraclostrobin ($41.75 ha1) and azoxystrobin ($53.08 ha1) was used to calculate the fungicide cost, and the application cost was set at $20 ha1. Calculations of yield, dockage, pick and crop value mimicked the grading standards used by the Ontario dry bean industry for commercial production as much as possible. ROI was computed using the formula:

Environmental conditions at Exeter created two distinct microenvironments in 2005 and 2006, which directly influenced disease development (Table 3). In 2005, hot and dry weather conditions prevailed during the early growth stages at the E1 and E2 sites, which enhanced plant growth and suppressed disease development. This was followed by several precipitation events during the flowering period which enhanced disease development, resulting in moderate anthracnose symptoms by harvest. In contrast, frequent precipitation and moderate temperatures occurred in 2006, which enhanced disease development throughout the growing season and resulted in severe anthracnose symptoms in the experiments at sites E3 and E4. The differences in environmental conditions played a large role in determining the level of disease pressure at the experimental sites, more so than the initial differences in seed infection levels. Therefore, for discussion purposes, sites E1 and E2 were considered as low disease pressure sites, while E3 and E4 sites were considered as high disease pressure sites. At the Morden location, heavy precipitation at the end of

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Table 3 Environmental conditions for six experiments in 2005 and 2006. Parameter

Month

Exeter 2005

Exeter 2006

Exeter meana

Morden 2005

Morden 2006

Morden meanb

Monthly total precipitation (mm)

May June July August September

68 29 128 94 65

28 30 78 91 60

82 79 81 68 109

82 167 64 33 48

47 42 17 40 44

69 91 72 68 48

Mean daily temperature ( C)

May June July August September

11.9 21.9 21.7 20.9 18.0

14.3 19.0 22.2 20.8 15.4

13.1 18.4 20.5 19.9 16.1

10.8 18.0 20.6 18.5 15.3

13.0 19.1 22.2 20.1 14.2

12.2 17.3 20.1 19.3 13.7

a b

28 year mean (1978e2006). 30 year mean (1981e2010).

June resulted in severe flooding of some of the plots and forced the abandonment of both experiments in 2005 (Table 3). In 2006, temperatures were above average from late June to the end of the summer, and precipitation was low from planting until the beginning of August, which resulted in low disease pressure in both experiments. 3.2. Disease severity on leaf veins Disease severity on leaf veins was very low at 6 WAP and differences were only observed under higher disease pressure conditions at the E3 and E4 sites in the pyraclostrobin experiment (Table 4) and at the E4 site in azoxystrobin experiment (Table 5). At these sites, the IC had higher disease severity than the NIS and NIC, as well as the average of the fungicide treatments. The DCT treatments had lower disease severity scores than the Apron Maxx treatments, for both experiments at the E4 site at 6 WAP. Disease severity increased by 9 WAP at all of the E sites, and the IC had a higher disease rating than the NIS and the NIC at all sites (Tables 4 and 5). The NIS had lower diseases severity than the NIC at 9 WAP at E3 and E4 sites. At 9 WAP, the average of the fungicide treatments had lower ratings of leaf vein infection than the IC at all E sites, in both the pyraclostrobin and the azoxystrobin experiments. DCT had significantly lower disease severity than Apron Maxx at the E1, E2 and E4 sites in the pyraclostrobin experiment and at the all E sites in the azoxystrobin experiment. Among the single fungicide

application timings in 2005, the A timing gave a lower disease rating than B, C and D timings at E1 and E2 sites at 9 WAP in both experiments. In 2006, the B and C timings gave the lowest disease ratings in the pyraclostrobin experiment at E4 site (Table 4), and in the azoxystrobin experiment at E3 and E4 (Table 5). Among the sequential timings, A þ C had a lower disease rating than B þ C and B þ D at E2 site, while A þ C and B þ C had lower ratings than B þ D at E4 site at 9 WAP when pyraclostrobin was applied (Table 4). In the azoxystrobin experiment, A þ C gave the lowest disease rating at both E1 and E2 sites at 9 WAP, and B þ C had lower disease rating than B þ D timings at E3 and E4 sites (Table 5). A comparison of the single and sequential timings at 9 WAP showed that sequential timing provided better control of anthracnose on the leaves at E3 and E4 sites when pyraclostrobin was applied (Table 4), and at 11 WAP at all E sites when azoxystrobin was applied (Table 5). 3.3. Disease severity on pods The IC consistently had higher disease ratings on pods than the NIS at all sites, and higher ratings than NIC at sites E1 and E2 in both experiments and at E3 site in the pyraclostrobin experiment (Tables 5 and 6). The NIC constantly had higher disease severity on pods than NIS at high disease pressure sites and at 11 WAP at low disease pressure sites (E1, E2). The IC had higher disease severity on pods than the average of the fungicide treatments, at all sites. DCT was more effective in reducing anthracnose severity on the pods

Table 4 Contrasts comparing dry bean anthracnose severity on leaf veins (6 WAP and 9 WAP) for DCT and Apron Maxx treated seed with various timings of pyraclostrobin at Exeter ON. Treatment comparison

Disease severity on leaf veins (%) 6 WAP E1

a

IC vs NIS IC vs NIC NIS vs NIC IC vs Treated DCT vs Apron Maxx b Timing A vs Timing B Timing A vs Timing C Timing A vs Timing D Timing B vs Timing C Timing B vs Timing D Timing C vs Timing D Timing AC vs Timing BC Timing AC vs Timing BD Timing BC vs Timing BD A,B,C,D vs AC,BC,BD

0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.0

9 WAP E3a

E2 vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0

0.3 0.3 0.0 0.3 0.0 0.1 0.1 0.1 0.0 0.0 0.1 0.0 0.0 0.0 0.1

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

0.0 0.0 0.0 0.1 0.1 0.0 0.1 0.1 0.1 0.1 0.1 0.0 0.1 0.1 0.0

0.8 0.8 0.0 0.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

E4a vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

0.0** 0.0** 0.0 0.0** 0.0 0.0 0.0 0.1 0.0 0.1 0.1 0.0 0.0 0.0 0.0

2.9 2.9 0.0 2.9 0.1 0.2 0.2 0.2 1.4 1.4 1.0 0.1 0.1 1.2 0.9

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

0.0** 0.0** 0.0 0.8** 1.5** 1.4** 1.0* 0.9* 1.0 0.9 0.9 1.2** 0.9 0.9 0.7

E1s

E2l

E3l

E4l

11 vs 1** 11 vs 2** 1 vs 2 11 vs 2** 1 vs 2** 0 vs 1* 0 vs 1** 0 vs 2** 1 vs 1 1 vs 2 1 vs 2 1 vs 2 1 vs 2 2 vs 2 1 vs 1

52 vs 10** 52 vs 2** 10 vs 2 52 vs 14** 5 vs 22** 1 vs 12** 1 vs 15** 1 vs 27** 12 vs 15 12 vs 27 15 vs 27* 2 vs 16** 2 vs 23** 16 vs 23 14 vs 13

49 vs 0** 49 vs 6** 0 vs 6* 49 vs 1** 0 vs 2 3 vs 1 3 vs 0 3 vs 6 1 vs 0 1 vs 6 0 vs 6 0 vs 0 0 vs 0 0 vs 0 2 vs 0*

69 vs 0** 69 vs 27** 0 vs 27** 69 vs 7** 4 vs 10** 16 vs 3** 16 vs 3** 16 vs 27* 3 vs 3 3 vs 27** 3 vs 27** 0 vs 0 0 vs 2** 0 vs 2** 12 vs 1**

Note: Data transformation carried out for analysis and back transformed means are presented; l, log transformation; a, Sin1; s, Square root. *,** Denotes significance at P < 0.05 and P < 0.01, respectively. a Abbreviations: IC, Infected Control; NIS, Non Infected Spray þ Pyraclostrobin; NIC, Non Infected Control; E1, Exeter 2005 low infection; E2, Exeter 2005 high infection; E3, Exeter 2006 low infection; E4, Exeter 2006 high infection. b Timing: A, 5-6 trifoliolate (V5); B, first flower (R1); C, mid flower (R2); D, early pod (R4).

C.L. Gillard et al. / Crop Protection 37 (2012) 81e90

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Table 5 Contrasts comparing dry bean anthracnose severity on leaf veins (6 WAP and 9 WAP) and pods (9 WAP and 11 WAP) for DCT and Apron Maxx treated seed with various timings of azoxystrobin at Exeter ON. Treatment comparison

Disease severity on leaf veins (%) 6 WAP E1,2,3

a

IC vs NIS IC vs NIC NIS vs NIC IC vs Treated DCT vs Apron Maxx b Timing A vs Timing B Timing A vs Timing C Timing A vs Timing D Timing B vs Timing C Timing B vs Timing D Timing C vs Timing D Timing AC vs Timing BC Timing AC vs Timing BD Timing BC vs Timing BD A,B,C,D vs AC,BC,BD

1.0 1.0 0.0 1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

E4 0.0 0.0 0.0 0.0 0.2 0.0 0.0 0.3 0.0 0.3 0.3 0.0 0.1 0.1 0.0

Disease severity on pods (%) 9 WAP

a

2.3 2.3 0.0 2.3 0.2 0.4 0.4 0.4 0.5 0.5 1.0 0.8 0.8 1.1 0.8

E1,2 vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

0.0** 0.0** 0.0 0.9** 1.7** 0.5 1.0 1.3 1.0 1.3 1.3 1.1 1.5 1.5 1.1

l

46 vs 3** 46 vs 5** 3 vs 5 46 vs 12** 6 vs 17** 5 vs 20** 5 vs 12** 5 vs 16** 20 vs 12 20 vs 16 12 vs 16 2 vs 13** 2 vs 16* 13 vs 16 13 vs 10*

9 WAP E3,4

l

11 WAP

l

71 vs 0** 71 vs 26* 0 vs 26** 71 vs 14** 10 vs 17** 32 vs 5** 32 vs 12** 32 vs 34 5 vs 12 5 vs 34** 12 vs 34** 4 vs 2 4 vs 7 2 vs 7* 21 vs 4**

l

E1,2

E3,4

46 vs 6** 46 vs 6** 6 vs 6 46 vs 15** 8 vs 22** 5 vs 22** 5 vs 17** 5 vs 20** 22 vs 17 22 vs 20 17 vs 20 4 vs 16** 4 vs 19 16 vs 19 16 vs 13

46 vs 2** 46 vs 29 2 vs 29** 46 vs 17** 16 vs 20** 31 vs 9** 31 vs 17* 31 vs 31 9 vs 17 9 vs 31** 17 vs 31* 8 vs 6 8 vs 15 6 vs 15* 22 vs 10**

E1,2 64 64 16 64 23 24 24 24 20 20 39 19 19 19 32

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

E3,4 16** 36** 36** 27** 31** 20 39** 46** 39** 46** 46 19 21 21 19**

49 vs 3** 49 vs 56 3 vs 56** 49 vs 20** 18 vs 24 41 vs 16** 41 vs 23** 41 vs 34 16 vs 23 16 vs 34** 23 vs 34 13 vs 4 13 vs 13 4 vs 13 29 vs 10**

*,**

Denotes significance at P < 0.05 and P < 0.01, respectively. Note: Data transformation carried out for analysis and back transformed means are presented; l, log transformation; a, Sin1. a Abbreviations: IC, Infected Control; NIS, Non Infected Spray þ Azoxystrobin; NIC, Uninfected Control; E1, Exeter 2005 low infection; E2, Exeter 2005 high infection; E3, Exeter 2006 low infection; E4, Exeter 2006 high infection. b Timing: A, 5-6 trifoliolate (V5); B, first flower (R1); C, mid flower (R2); D, early pod (R4).

than Apron Maxx at all sites except E3 and E4 sites at 11 WAP in azoxystrobin experiment. Among the single application treatments in the azoxystrobin experiments, the A timing resulted in lower disease severity on pods than the B, C and D timings at E1 and E2 sites at 9 WAP, and the A and B timings were superior to the C and D timings at 11 WAP (Table 5). At the E3 and E4 sites, timings B and C had lower disease severity on pods than the A and D timings at 9 WAP and 11 WAP. For the sequential timings at 9 WAP, A þ C was superior to B þ C at E1 and E2, while B þ C was superior to B þ D at E3 and E4 (Table 5). No differences were observed for disease severity on pods between the sequential timings at 11 WAP. For the pyraclostrobin experiments, the A timing had better control of disease severity on pods over the B and D timing at 9 WAP at E1 and E2 sites, but was only better than the D timing at 11 WAP. Generally, the B and C timing had lower disease severity on pods at 9 WAP and 11 WAP at E3 and E4 sites than the other single application

treatments, and A, B and C provided equal control of disease severity on pods at the M1 and M2 sites. Contrasts comparing sequential timings at 9 WAP showed that the A þ C timing was better for reducing disease severity on pods than B þ C at E1 and E2 sites, and B þ C was better than B þ D at E3 and E4 sites. No differences were observed between the sequential timings at any site at 11 WAP. The sequential fungicide timings had lower disease severity on pods than the single fungicide timings at all sites except at E1 and E2 sites at 9 WAP in both experiments. 3.4. Plant maturity Contrast comparisons in the pyraclostrobin and azoxystrobin experiments show that the NIS matured 6e8 days later than the IC under low disease pressure at E1 and E2 and 3e5 days later under high disease pressure at E3 (Tables 7 and 8). Similar differences were

Table 6 Contrasts comparing dry bean anthracnose severity on pods (9 and 11 WAP) for DCT and Apron Maxx treated seed with various timings of pyraclostrobin at Exeter ON and Morden MB. Treatment comparison

Disease severity on pods (%) 9 WAP

a

IC vs NIS IC vs NIC NIS vs NIC IC vs Treated DCT vs Apron Maxx b Timing A vs Timing B Timing A vs Timing C Timing A vs Timing D Timing B vs Timing C Timing B vs Timing D Timing C vs Timing D Timing AC vs Timing BC Timing AC vs Timing BD Timing BC vs Timing BD A,B,C,D vs AC,BC,BD *,**

11 WAP

E1,2l

E3,4l

E1,2

34 vs 6** 34 vs 2** 6 vs 2 34 vs 8** 3 vs 12** 2 vs 9* 2 vs 8 2 vs 11* 9 vs 8 9 vs 11 8 vs 11 3 vs 8* 3 vs 12 8 vs 12 7 vs 8

54 vs 1** 54 vs 29 1 vs 29** 54 vs 12** 8 vs 16** 26 vs 11 26 vs 6** 26 vs 34 11 vs 6 11 vs 34** 6 vs 34** 3 vs 1 3 vs 7 1 vs 7* 19 vs 4**

73 73 15 73 20 23 23 23 21 21 31 16 16 18 29

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

15** 52** 52** 24** 28** 21 31 39** 31* 39** 39* 18 19 19 18**

E3s

E4

M1,M2a

54 vs 0** 54 vs 31** 0 vs 31** 54 vs 7** 6 vs 9* 17 vs 7** 17 vs 5** 17 vs 18 7 vs 5 7 vs 18** 5 vs 18** 2 vs 2 2 vs 2 2 vs 2 12 vs 2**

40 vs 0** 40 vs 42 0 vs 42** 40 vs 16** 14 vs 19** 37 vs 25** 37 vs 13** 37 vs 31 25 vs 13** 25 vs 31 13 vs 31** 4 vs 0 4 vs 4 0 vs 4 27 vs 3**

4 4 0 4 0 0 0 0 1 1 1 0 0 0 1

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

0** 0** 0 1** 1** 1 1 2** 1 2 2** 0 1 1 0**

Denotes significance at P < 0.05 and P < 0.01, respectively. Note: Data transformation carried out for analysis and back transformed means are presented; l, log transformation, a, Sin1; s, Square root. a Abbreviations: IC, Infected Control; NIS, Non Infected Spray þ Pyraclostrobin; NIC, Non Infected Control; E1, Exeter 2005 low infection; E2, Exeter 2005 high infection; E3, Exeter 2006 low infection; E4, Exeter 2006 high infection; M1, Morden 2006 low infection; M2, Morden 2006 high infection. b Timing: A, 5-6 trifoliolate (V5); B, first flower (R1); C, mid flower (R2); D, early pod (R4).

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Table 7 Contrasts comparing dry bean plant maturity, seed yield, seed dockage and seed weight for DCT and Apron Maxx treated seed with various timings of pyraclostrobin at Exeter ON and Morden MB. Treatment comparison

Plant maturity (days after planting)

Yield E1,2s

a

E3

E1,2 a

IC vs NIS IC vs NIC NIS vs NIC IC vs Treated DCT vs Apron Maxx b Timing A vs Timing B Timing A vs Timing C Timing A vs Timing D Timing B vs Timing C Timing B vs Timing D Timing C vs Timing D Timing AC vs Timing BC Timing AC vs Timing BD Timing BC vs Timing BD A,B,C,D vs AC,BC,BD

78 78 86 78 86 85 85 85 86 86 83 87 87 87 84

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

86** 82* 82* 85** 84** 86 83* 82** 83* 82** 82 87 86 86 86**

86 86 91 86 90 89 89 89 89 89 90 91 91 91 89

E3 1

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

91** 87 87** 90** 90 89 90 89 90 89 89 91 91 91 91**

p

kg ha

%

925 vs 1750** 925 vs 1521** 1750 vs 1521 925 vs 1532** 1631 vs 1434** 1703 vs 1527 1703 vs 1327** 1703 vs 1341** 1527 vs 1327 1527 vs 1341 1327 vs 1341 1799 vs 1518* 1799 vs 1509 1518 vs 1509 1474 vs 1609*

89 64 66 14 28 27

19

9

E4

kg ha

1

1143 1143 2829 1143 2614 2259 2259 2259 2553 2553 2611 2640 2640 2932 2394

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

% 2829** 2156** 2156** 2559** 2502 2553* 2611* 2151 2611 2151** 2151** 2932* 2764 2764 2779**

M1,2 1

p

148 89 31 124 13 16

19 21 11

16

p

kg ha

%

571 vs 2875** 571 vs 1045** 2875 vs 1045** 571 vs 1955** 2177 vs 1733** 1154 vs 1936** 1154 vs 1998** 1154 vs 1281 1936 vs 1998 1936 vs 1281** 1998 vs 1281** 2493 vs 2534 2493 vs 2287* 2534 vs 2287* 1592 vs 2438**

404 83 175 242 26 68 73

51 56 9 11 53

3775 3775 3658 3775 4016 3883 3883 3883 4216 4216 3977 4209 4209 3626 3998

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

3658 3931 3931 3962 3908 4216 3977 3917 3977 3917 3917 3626 3906 3906 3914

*,**

Denotes significance at P < 0.05 and P < 0.01, respectively. p Difference in percentage between two contrasts of the yield values. Note: Data transformation carried out for analysis and back transformed means are presented; a, Sin1; s, Square root. a Abbreviations: IC, Infected Control; NIS, Non Infected Spray þ Pyraclostrobin; NIC, Non Infected Control; E1, Exeter 2005 low infection; E2, Exeter 2005 high infection; E3, Exeter 2006 low infection; E4, Exeter 2006 high infection; M1, Morden 2006 low infection; M2, Morden 2006 high infection. b Timing: A, 5-6 trifoliolate (V5); B, first flower (R1); C, mid flower (R2); D, early pod (R4).

observed between the IC and the average of the fungicide treatments. Plant maturity data was not collected for the E4, M1 and M2 sites. DCT delayed plant maturity by as much as two days, compared to Apron Maxx. Compared to later fungicide application timings, a single application of fungicide at the A or B timing provided resulted in a 2e4 day delay in maturity in the pyraclostrobin experiment, and a 3 day delay in maturity in the azoxystrobin experiment. The sequential fungicide timings matured 2e3 days later than the single timings in both experiments at all sites. 3.5. Seed yield Contrast comparisons of the NIS and the IC showed that NIS produced a 65e89% higher yield at E1 and E2, and a 148e404%

higher yield at E3 and E4 (Tables 7 and 8). Yield increases due to planting of disease free seed (NIC) were 64e70% at E1 and E2, and 83e99% at E3 and E4, when compared to IC. Yield differences between the NIS and the NIC were 31e175%. The average of all fungicide treatments produced a yield increase of 53e66% at E1 and E2, and 124e242% at E3 and E4, compared to the IC. Seed treated with DCT yielded 13e26% more than Apron Maxx, in seven of eight environments. Under low disease pressure (E1 and E2), a single fungicide application at the A timing resulted in a 27% and 28% yield increase over the C and D timings in the pyraclostrobin experiment, respectively, and a 19% yield increase over the D timing in the azoxystrobin experiment. Under high disease pressure (E3 and E4), the B and C timings produced a 13e73% yield increase over the A timing, and a 19e71% yield increase over the D timing. For the

Table 8 Contrasts comparing dry bean plant maturity, seed yield, seed dockage and seed weight for DCT and Apron Maxx treated seed with various timings of azoxystrobin at Exeter ON. Treatment comparison

Plant maturity (days after planting)

Yield E1,2

E1,2l a

IC vs NIS IC vs NIC NIS vs NIC IC vs Treated DCT vs Apron Maxx b Timing A vs Timing B Timing A vs Timing C Timing A vs Timing D Timing B vs Timing C Timing B vs Timing D Timing C vs Timing D Timing AC vs Timing BC Timing AC vs Timing BD Timing BC vs Timing BD A,B,C,D vs AC,BC,BD *,**

79 79 85 79 84 83 83 83 83 83 82 85 85 85 82

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

**

85 84* 84 83** 82** 83 82 80* 82 80* 80 85 84 84 84**

86 86 89 86 90 88 88 88 89 89 88 90 90 90 88

E3,4

kg ha1

E3l vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

**

89 86 86** 89** 89** 89** 88* 88 88 88** 88 90 92 92** 91**

Seed weight (g 100 seed1)

Dock (%)

s

%p **

855 vs 1415 855 vs 1455** 1415 vs 1455 855 vs 1306** 1396 vs 1216** 1440 vs 1228 1440 vs 1284 1440 vs 1210** 1228 vs 1284 1228 vs 1210 1284 vs 1210 1425 vs 1299 1425 vs 1245 1299 vs 1245 1293 vs 1323

65 70 53 15

19

kg ha1

%p **

579 vs 2592 579 vs 1150** 2592 vs 1150** 579 vs 1764** 1875 vs 1653** 1241 vs 1936** 1241 vs 1704** 1241 vs 1131 1936 vs 1704 1936 vs 1131** 1704 vs 1131** 2007 vs 2268 2007 vs 2059 2268 vs 2059 1503 vs 2111**

348 99 124 205 13 56 37

71 51

40

E1,2l

E3,4l **

15 vs 2 1 15 vs 8* 2 vs 8** 15 vs 6** 5 vs 6** 5 vs 3 5 vs 12** 5 vs 11** 3 vs 12** 3 vs 11** 12 vs 11 4 vs 2 4 vs 3 2 vs 3 8 vs 3**

E1,2s **

21 vs 2 21 vs 13* 2 vs 13** 21 vs 8* 7 vs 9** 13 vs 6** 13 vs 8** 13 vs 14 6 vs 8 6 vs 14** 8 vs 14** 6 vs 4* 6 vs 5 4 vs 5 10 vs 5**

13 13 15 13 15 15 15 15 14 14 15 15 15 15 15

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

E3,4 15** 15** 15 15** 14** 14* 15 14* 15 14 14 15 15 15 15

15 15 17 15 16 16 16 16 17 17 16 17 17 17 16

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

17** 15 15** 16** 16 17 16 15 16 15** 15* 17 17 17 17**

Denotes significance at P < 0.05 and P < 0.01, respectively. p Difference in percentage between two contrasts of the yield values. Note: Data transformation carried out for analysis and back transformed means are presented; l, log transformation, s, Square root. a Abbreviations: IC, Infected Control; NIS, Non Infected Spray þ Azoxystrobin; NIC, Non Infected Control; E1, Exeter 2005 low infection; E2, Exeter 2005 high infection; E3, Exeter 2006 low infection; E4, Exeter 2006 high infection. b Timing: A, 5-6 trifoliolate (V5); B, first flower (R1); C, mid flower (R2); D, early pod (R4).

C.L. Gillard et al. / Crop Protection 37 (2012) 81e90

87

sequential fungicide treatments, relatively minor differences were detected in only the pyraclostrobin experiment. Contrasts comparing the single and sequential timings showed that the sequential application of fungicides produced yield increases of between 9 and 53%, in six of eight environments. No differences were observed between treatments for seed yield at the M1 and M2 sites, which was likely due to low disease levels.

E4 sites. A comparison of the sequential timings showed that A þ C had a higher seed weight than B þ C at the E1 and E2 sites. The sequential timings had higher seed weight than the single timings at all E sites. The experiments at the Morden location produced no treatment differences for seed weight, due to low disease pressure.

3.6. Dockage

The NIS had lower pick than the IC at all sites, and lower pick than the NIC at all of the E sites (Tables 10 and 11). The NIC had lower pick than the IC, under lower disease pressure (E1, E2, M1, M2). The average of the fungicide treatments had a lower pick than the IC at all sites, while DCT produced a lower pick than Apron Maxx under lower disease pressure in both experiments. A contrast comparing the single fungicide application timings showed that timing A and B had the lowest pick at E1 and E2, while timing B and C had lowest pick at E3 and E4 sites. Timing D had a higher pick value than all other timings at M1 and M2. No differences in pick were measured between the sequential timings at any site, but the sequential timing had lower pick values than the single timings at all sites.

The dockage results discussed will focus on the Exeter location, due to a lack of treatment response at the Morden location. In both experiments, the NIS and the NIC had lower dockage than the IC, while the NIS had lower dockage than NIC (Tables 8 and 9). The average of the fungicide treatments also had lower dockage than the IC. DCT had a lower dockage than Apron Maxx at all sites in the azoxystrobin experiment, but at only one site in the pyraclostrobin experiment. Under lower disease pressure, a single fungicide application at timings A or B had the lowest dockage, but under higher disease pressure, timings B and C had the lowest dockage. For the sequential timings, B þ C timing had the lower dockage than the A þ C timing at three of eight sites. In addition, the sequential applications produced lower dockage than the single applications, in all of the Exeter environments. 3.7. Seed weight The NIS had higher seed weight than the IC at all E sites, and higher seed weight than the NIC only at E3 and E4 sites. The seed weight of the NIC was higher than the IC at E1 and E2 sites. The average of the fungicide treatments had a higher seed weight than IC at all the E sites, while DCT had a higher seed weight than Apron Maxx at E1 and E2 only. In the azoxystrobin experiment, seed weight at the A timing was higher than the B and D timing at E1 and E2, while the B and C timings were higher than D at E3 and E4 sites. There were no differences in seed weight among the sequential application timings, but the sequential timings had higher seed weights than the single timings at E3 and E4 sites. In the pyraclostrobin experiment, the A timing produced a higher seed weight than the C and D timing at E1 and E2 sites. The B and C timings produced higher seed weights than the A timing at E3 and

3.8. Pick

3.9. Return on investment (ROI) The ROI results presented will focus on the four E sites, due to a lack of treatment response at the Morden location. The NIS had the highest ROI while the IC had the lowest ROI at all sites (Tables 11 and 12). The difference in ROI between treatments ranged from $235e$825 ha1. The NIC had a higher ROI than the IC at four sites, but had a lower ROI than the NIS at all eight sites. Compared to the IC, the average of the fungicide treatments increased the ROI by $177e179 ha1 in the azoxystrobin experiment, and $455e469 ha1 in the pyraclostrobin experiment. The difference in ROI between DCT and Apron Maxx ranged from $95 ha1 in the azoxystrobin experiment to $106e137 ha1 in the pyraclostrobin experiment. For the single fungicide application timings, timings A and B increased the ROI by $215e346 ha1, compared to timings C and D under low disease pressure. Timing B and C increased the ROI by $168e292 ha1, compared to the timing A and D under high disease pressure. In both instances, higher returns were recorded for the pyraclostrobin experiment. There were no differences in ROI

Table 9 Contrasts comparing dry bean anthracnose severity on dockage and seed weight for DCT and Apron Maxx treated seed with various timings of pyraclostrobin at Exeter ON and Morden MB. Treatment comparison

a

IC vs NIS IC vs NIC NIS vs NIC IC vs Treated DCT vs Apron Maxx b Timing A vs Timing B Timing A vs Timing C Timing A vs Timing D Timing B vs Timing C Timing B vs Timing D Timing C vs Timing D Timing AC vs Timing BC Timing AC vs Timing BD Timing BC vs Timing BD A,B,C,D vs AC,BC,BD *,**

Seed weight (g 100 seed1)

Dock (%) E1s

E2s

E3s

E4s

M1,2

E1,2

14 vs 1** 14 vs 10** 1 vs 10** 14 vs 3** 3 vs 3 1 vs 2 1 vs 3** 1 vs 8** 2 vs 4** 2 vs 8** 4 vs 8 1 vs 1 1 vs 1 1 vs 1 5 vs 1**

19 vs 1** 19 vs 6** 1 vs 6** 19 vs 5** 5 vs 5 3 vs 1** 3 vs 11** 3 vs 13** 1 vs 11** 1 vs 13** 11 vs 13* 2 vs 1** 2 vs 1 1 vs 1 7 vs 1**

11 vs 1** 11 vs 6** 1 vs 6** 11 vs 3** 3 vs 3 4 vs 3 4 vs 2* 4 vs 6 3 vs 2 3 vs 6** 2 vs 6** 2 vs 1 2 vs 2 1 vs 2 4 vs 2**

24 vs 2** 24 vs 13** 2 vs 13** 24 vs 6** 5 vs 7** 13 vs 6** 13 vs 5** 13 vs 10* 6 vs 5 6 vs 10** 5 vs 10** 4 vs 3 4 vs 4 3 vs 4 9 vs 3**

4 4 5 4 5 5 5 5 4 4 4 5 5 5 5

13 13 16 13 16 16 16 16 15 15 15 16 16 15 15

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

5 4 4 5 5 4 4 5 4 5 5 5 5 5 5

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

E3,4 16** 15** 15 15** 15** 15 15* 15** 15 15 15 15* 16 16 16**

15 15 17 15 17 16 16 16 17 17 17 17 17 17 17

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

M1 17** 16 16** 17** 17 17* 17** 17 17 17 17 17 17 17 18**

43 43 42 43 43 43 43 43 42 42 42 43 43 43 42

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

M2 42 43 43 42 42 42 42 42 42 42 42 43 43 43 43

41 41 41 41 42 42 42 41 41 41 41 42 42 42 42

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

41 41 41 42 41 41 41 41 41 41 41 42 42 42 42

Denotes significance at P < 0.05 and P < 0.01, respectively. Note: Data transformation carried out for analysis and back transformed means are presented; s, Square root. a Abbreviations: IC, Infected Control; NIS, Non Infected Spray þ Pyraclostrobin; NIC, Non Infected Control; E1, Exeter 2005 low infection; E2, Exeter 2005 high infection; E3, Exeter 2006 low infection; E4, Exeter 2006 high infection; M1, Morden 2006 low infection; M2, Morden 2006 high infection. b Timing: A, 5-6 trifoliolate (V5); B, first flower (R1); C, mid flower (R2); D, early pod (R4).

88

C.L. Gillard et al. / Crop Protection 37 (2012) 81e90

Table 10 Contrasts comparing dry bean anthracnose severity on pick for DCT and Apron Maxx treated seed with various timings of pyraclostrobin at Exeter ON and Morden MB. Treatment comparison

Pick (%) E1s

E2

E3,4

a

37 vs 3** 37 vs 24** 3 vs 24** 37 vs 7** 4 vs 10** 4 vs 3 4 vs 6** 4 vs 19** 3 vs 6** 3 vs 19** 6 vs 19 2 vs 2 2 vs 1 2 vs 1 11 vs 2**

42 vs 3** 42 vs 21** 3 vs 21** 42 vs 12** 12 vs 13 12 vs 5** 12 vs 27** 12 vs 30** 5 vs 27** 5 vs 30** 27 vs 30 6 vs 2 6 vs 4 2 vs 4 19 vs 4**

45 45 10 45 22 35 35 35 26 26 24 16 16 14 29

IC vs NIS IC vs NIC NIS vs NIC IC vs Treated DCT vs Apron Maxx Timing A vs Timing Bb Timing A vs Timing C Timing A vs Timing D Timing B vs Timing C Timing B vs Timing D Timing C vs Timing D Timing AC vs Timing BC Timing AC vs Timing BD Timing BC vs Timing BD A,B,C,D vs AC,BC,BD

Treatment comparison

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

M1l 10** 42 42** 24** 26 26* 24** 32 24 32 32* 14 18 18 16**

6 6 0 6 1 1 1 1 2 2 1 1 1 1 2

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

M2s 0** 0** 0 2** 2** 2 1 4** 1 4* 4** 1 1 1 1*

5 5 1 5 1 1 1 1 1 1 1 0 0 1 2

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

1** 0** 0 1** 2** 1 1 4** 1 4** 4** 1 1 1 1*

*,**

Denotes significance at P < 0.05 and P < 0.01, respectively. Note: Data transformation carried out for analysis and back transformed means are presented; l, log transformation, s, Square root. a Abbreviations: IC, Infected Control; NIS, Non Infected Spray þ Pyraclostrobin; NIC, Non Infected Control; E1, Exeter 2005 low infection; E2, Exeter 2005 high infection; E3, Exeter 2006 low infection; E4, Exeter 2006 high infection; M1, Morden 2006 low infection; M2, Morden 2006 high infection. b Timing: A, 5-6 trifoliolate (V5); B, first flower (R1); C, mid flower (R2); D, early pod (R4).

between the sequential fungicide timings at any site. The ROI for the sequential timings was 9e13% less than the NIS under low disease pressure, and 27e56% less than the NIS under higher disease pressure. The additional return from two fungicide applications, compared to one application ranged from $83e179 ha1 in the azoxystrobin experiment, to $210e338 ha1 in the pyraclostrobin experiment. 4. Discussion This study demonstrates that the use of an appropriate seed treatment followed by the application of a fungicide at the correct Table 11 Contrasts comparing dry bean seed pick and seed quality and crop value for DCT and Apron Maxx treated seed with various timings of azoxystrobin at Exeter ON. Treatment comparison

a

IC vs NIS IC vs NIC NIS vs NIC IC vs Treated DCT vs Apron Maxx b Timing A vs Timing B Timing A vs Timing C Timing A vs Timing D Timing B vs Timing C Timing B vs Timing D Timing C vs Timing D Timing AC vs Timing BC Timing AC vs Timing BD Timing BC vs Timing BD A,B,C,D vs AC,BC,BD *,**

ROI ($ ha1)

Pick (%) s

Table 12 Contrasts comparing dry bean seed quality and crop value for DCT and Apron Maxx treated seed with various timings of pyraclostrobin at Exeter ON and Morden MB.

E1,2

E3,4

34 vs 6** 34 vs 25 6 vs 25** 34 vs 16** 14 vs 18* 15 vs 10 15 vs 31** 15 vs 30** 10 vs 31** 10 vs 30** 31 vs 30 9 vs 8 9 vs 10 8 vs 10 22 vs 9**

42 42 18 42 32 41 41 41 31 31 32 30 30 26 36

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

E1,2 18** 44 44** 32* 32 31* 32* 41 32 41* 41* 26 25 25 27**

109 109 344 109 334 366 366 366 369 369 151 360 360 350 255

E3,4 vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

341* 329* 329 288** 239** 369 151** 141** 151** 141** 141 350 303 303 338**

32 vs 542** 32 vs 54 542 vs 54** 32 vs 209** 228 vs 189 35 vs 255* 35 vs 216 35 vs 48 255 vs 216 255 vs 48* 216 vs 48 236 vs 363 236 vs 363 363 vs 363 139 vs 318**

Denotes significance at P < 0.05 and P < 0.01, respectively. ROI: return on investment. Note: Data transformation carried out for analysis and back transformed means are presented, l, log transformation; s, Square root. a Abbreviations: IC, Infected Control; NIS, Non Infected Spray þ Azoxystrobin; NIC, Non Infected Control; E1, Exeter 2005 low infection; E2, Exeter 2005 high infection; E3, Exeter 2006 low infection; E4, Exeter 2006 high infection. b Timing: A, 5-6 trifoliolate (V5); B, first flower (R1); C, mid flower (R2); D, early pod (R4).

a

IC vs NIS IC vs NIC NIS vs NIC IC vs Treated DCT vs Apron Maxx b Timing A vs Timing B Timing A vs Timing C Timing A vs Timing D Timing B vs Timing C Timing B vs Timing D Timing C vs Timing D Timing AC vs Timing BC Timing AC vs Timing BD Timing BC vs Timing BD A,B,C,D vs AC,BC,BD

ROI ($ ha1) E1,2

E3,4

M1,2

77 vs 726** 77 vs 351** 726 vs 351** 77 vs 546** 600 vs 494** 620 vs 625 620 vs 301** 620 vs 279** 625 vs 301** 625 vs 279** 301 vs 279 721 vs 647 721 vs 632 647 vs 632 457 vs 667**

32 vs 857** 32 vs 175 857 vs 175** 32 vs 487** 556 vs 419* 212 vs 442* 212 vs 504** 212 vs 229 442 vs 504 442 vs 229* 504 vs 229** 664 vs 768 664 vs 627 768 vs 627 348 vs 686**

1388 1388 1317 1388 1534 1499 1499 1499 1627 1627 1546 1614 1614 1369 1521

vs vs vs vs vs vs vs vs vs vs vs vs vs vs vs

1317 1625 1625 1490 1446 1627 1618 1412 1546 1412 1412 1369 1478 1478 1488

*,**

Denotes significance at P < 0.05 and P < 0.01, respectively. ROI: return on investment. a Abbreviations: IC, Infected Control; NIS, Non Infected Spray þ Pyraclostrobin; NIC, Non Infected Control; E1, Exeter 2005 low infection; E2, Exeter 2005 high infection; E3, Exeter 2006 low infection; E4, Exeter 2006 high infection; M1, Morden 2006 low infection; M2, Morden 2006 high infection. b Timing: A, 5-6 trifoliolate (V5); B, first flower (R1); C, mid flower (R2); D, early pod (R4).

timing plays an important role in dry bean anthracnose disease management and improve yield. Seed-borne infection causes severe anthracnose symptoms in dry bean (Conner et al., 2009), with favourable environmental conditions for the disease development. Rainfall patterns documented during the study period indicate that amount and distribution of precipitation plays an important role in disease development, and in creating different levels of disease pressure at the experimental sites. Anthracnose disease management through the application of foliar and seed treatment fungicides is a common practice among growers. Results of this study show that seed-borne infection can be controlled by a combination of seed-treatment and foliar fungicide applications under different environmental conditions. Foliar application of pyraclostrobin or azoxystrobin in the noninfected sprayed control (NIS) produced better results than the infected control (IC) for almost all of the parameters examined, under low and high disease pressure at Exeter ON. The non-infected control (NIC) tended to have higher disease pressure than the NIS, which was likely due to the spread of anthracnose from adjacent plots to the NIC later in the growing period. This was particularly evident at the high disease pressure sites (E3 and E4), which received regular precipitation throughout the growing season. Similar findings have been reported in the literature (Mohammed and Somsiri, 2007). The low disease severity on pods recorded at M1 and M2 indicates a very low level of disease pressure at Morden MB sites in 2006. Results from this study suggest that the seed treatments evaluated had an impact on disease expression, which agrees with other published work (Pynenburg et al., 2011). It was observed that there was a positive relationship between plant maturity and anthracnose control. Anthracnose damages the plant’s vascular system, leading to the dehydration of leaf tissue, premature leaf senescence and defoliation (Gaunt, 1995; Bassanezi et al., 2001), which directly impacts plant maturity. In general, the seed treatments and foliar fungicides that were evaluated in this study reduced disease severity, which in turn promoted plant health and delayed plant maturity. The treatment differences for seed yield were quite dramatic, particularly at sites with high disease pressure. The yield increase in NIS at low and high disease

C.L. Gillard et al. / Crop Protection 37 (2012) 81e90

sites was attributed to the control of seed-borne disease, as well as the control of late season cross infection from neighbouring plots. Although direct comparisons cannot be made, seed yields appear to be higher in the pyraclostrobin experiment than the azoxystrobin, and the yield response to the treatments tended to be more pronounced. This agrees with similar research (Gillard et al., 2012) that was conducted under the same conditions. The high yields obtained in the fungicide treated plots could be attributed to low disease severity on leaves and pods. As expected yield differences between treatments were generally greater at the high disease sites (E3 and E4) than at the low disease sites (E1 and E2), in both experiments. The photosynthesis efficiency of the green leaf area surrounding an anthracnose lesion is greatly reduced, regardless of the size of the lesion (Bassanezi et al., 2001; Lopes and Berger, 2001). There were significant reduction in dockage and pick in the fungicide treated plots. In general, treatments that had low dockage had higher seed weights. Anthracnose directly affects dry matter assimilation in the seed, so infected plants frequently produce smaller seeds with higher dockage (Gillard et al., 2012; Pynenburg et al., 2011). Pick values are strongly affected by the severity of pod infection, so it is not surprising that treatment differences for pick are similar to treatment differences for disease severities on pods. Similar results were documented in a related study (Gillard et al., 2012). The differences in ROI between the highest (NIS) and the lowest (IC) treatments show the range in potential economic returns to disease management, since these two treatments represent the extremes for disease control in this study. The NIS achieved the highest ROI under both low and high disease pressure, due to a combination of high yield and low dockage and pick values, which were directly related to the high level of disease control. Differences were evident between DCT and Apron Maxx for leaf and pod disease severity, in most environments. DCT showed promising results when combined with azoxystrobin, particularly under lower disease pressure. The DCT treatments had lower disease severity, which resulted in lower dockage and pick and higher yields and ROI. Although DCT had lower disease ratings than Apron Maxx in the pyraclostrobin experiment, these differences were not always reflected in lower dock or pick values. It is apparent that DCT was the most effective seed treatment in combination with pyraclostrobin, providing higher yield at three of four of the Exeter sites, and higher ROI at all of the Exeter sites. DCT seemed to provide a more consistent ROI with pyraclostrobin than with azoxystrobin, which may be due to the higher efficacy of pyraclostrobin under favourable weather conditions for the disease development (Gillard et al., 2012). In 2005, the later fungicide timings B, C and D were not as effective as the A timing. An early pyraclostrobin application (A timing) effectively controlled leaf vein infection at 6 and 9 WAP (Table 4) at the low disease sites, and this resulted in lower disease severity on pods (Table 6) as well. Under higher disease pressure in 2006, rapid disease development started at the flowering stage (9 WAP), which coincided closely with the B and C fungicide timings. Therefore these timings were superior to the A timing in both experiments. In general, earlier fungicide application timings provided a higher yield than later application timings. Both fungicides are considered protective products, rather than curative (Bartlett et al., 2002). Sequential fungicide applications mainly showed differences for leaf disease severity. Under lower disease pressure, the best sequential was A þ C, while under higher disease pressure, a sequential application at A þ C or B þ C had the lowest leaf disease severity. A similar response was observed for disease severity on pods at 9 WAP, but disappeared by 11 WAP. Results from this study clearly indicate that the higher the disease severity in the canopy, the greater the yield losses. Yield differences between

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sequential timings were only documented in the pyraclostrobin experiment, and appear to be directly related to the differences seen in leaf vein disease severity. Generally, sequential timing treatments were superior to single timing treatments for all parameters, especially under high disease pressure (E3, E4 sites). The sequential timing treatments provided superior disease control and extended plant maturity, which agrees with previous research (Gillard et al., 2012). Differences in ROI between this study and a related study (Gillard et al., 2012) are quite remarkable. The current study showed a two fold higher ROI under lower disease pressure conditions in both experiments, and a two and four fold higher ROI under higher disease pressure conditions, for the pyraclostrobin and azoxystrobin experiments respectively. The higher ROI in this study were attributed to both higher yield and lower pick values. It is likely that the differences in ROI between this study and previous work was the additional disease control provided by the combination of seed treatment and sequential foliar spraying of fungicides, under high disease pressure conditions, compared to the use of foliar fungicides alone (Gillard et al., 2012). This agrees with other published work (Pynenburg et al., 2011). To conclude, this study confirmed that the seed-borne infection of dry bean anthracnose can be effectively controlled by the combined use of seed treatment fungicides and the sequential application of foliar fungicides. The seed treatment DCT reduced leaf and pod symptoms, pick and dock and increased yield and ROI, compared to Apron Maxx under both low and high disease pressure. As a result of the disease control provided by the combined effects of seed treatment and foliar fungicides, plant maturity and yield increased at all of the Exeter sites. A sequential fungicide application dramatically reduced disease severity on leaves and pods, as well as pick and dock values and increased plant maturity, yield and ROI, with only occasional differences between the three treatments. This consistency was not evident in a related study (Gillard et al., 2012), where the same foliar fungicides were evaluated in the absence of any seed treatment. It was our hope that the combination of an effective seed treatment and a single well timed application of a foliar fungicide would provide a high level of disease control and minimize any related loss in revenue, without the need for a second fungicide application. There is some evidence that this scenario is possible under the very low disease conditions that occurred at the Morden sites. Therefore, factors that should be considered when planning an anthracnose management program in dry beans include seed treatment, seed source, environmental conditions and the application timing of foliar fungicide. Growers should use an appropriate seed treatment and correctly time the first application of fungicide based on field scoutings. A second fungicide application may be necessary to effectively control dry bean anthracnose and maximize the ROI. Acknowledgements The authors express their sincere thanks to W.C. Penner, D.B. Stoesz and S. Willis for their technical support and C. Shropshire for her assistance with the statistical analysis. We appreciate the funding received from the Agricultural Adaptation Council CanAdvance Program, Pulse Canada, the Ontario White Bean Producers, the Ontario Coloured Bean Growers, the Manitoba Pulse Growers Association, BASF Canada and Syngenta Crop Protection to carry out this series of experiments. References Agricorp, 2006. Average Crop Insurance Values for Dry Bean Market Classes in Ontario. Agricop, Guelph, ON.

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