Wheat scab is common in Argentina mainly durum wheat and some bread varieties. The epidemics occur every 5 to 7 years. During the 2007, 2008, and 2009 growing seasons, three trials were conducted at the INTA Balcarce Experimental Station. Each plot had six rows of 5 m long, spaced 0.15 m apart and was set up in a randomized complete block design with four replications. Trifloxystrobin plus cyproconazole was sprayed at Z3.1 stage. Treatments were sprayed at Z6.1 stage with tebuconazole, prochloraz, and metconazole to improve scab control. Artificial inoculations were made in Z6.1. Severity of
Head blight (scab) caused by
In Argentina, the use of foliar fungicides on wheat is common, and it has increased considerably [
Yields can be improved with the use of fungicides, but yield increments vary extremely according to disease severity, fungicide efficiency, timing spray, and number of applications [
These sprayings produce healthy plants in advance crop stage, reducing the incidence or severity of wheat scab in the field. The objective of this work was to evaluate the effect of early and early plus flowering fungicide spray on the severity of scab in wheat field, as well as the disease’s yield and grain infection.
During the 2007, 2008, and 2009 growing seasons, three trials were conducted at the INTA Balcarce Experimental Station (Argentina) in a Brunizen soil with 3.9% of organic matter. ProInta Oasis wheat cultivar, bread type, susceptible to the foliar rust (
In tillering stage Zadoks 3.1 [
Inoculations were made 2 days after fungicide sprayings in Z61. A mixture of isolates of
Scab severity was rated at early dough stage [
Severity of
The percentage of infected seeds was determined by placing 100 seed per replication in 2% sodium hypochlorite for 15 sec, rinsing in water for 2 min, and placing seed in containers with moist cotton covered with moist filter paper. The containers were incubated in polyethylene bags to maintain high relative humidity during 8 days. Records included the percentage of grains with
Every year each experimental plot had six rows of 5 m long, spaced 0.15 m. Treatments were arranged in a randomized complete block design with four replicates. Data was subjected to analysis of variance, and means were compared by LSD at
During the evaluation years, significant differences were found between the control check in regards to scab severity, yield, infected kernels, and kernels weight variables. The rates of said variables in the untreated check show the levels of natural infection during test trials, but significant differences were detected between inoculation and no inoculation in the checks and show the efficiency of the artificial inoculation.
Leaf blotch and rust control by trifloxystrobin plus cyproconazolesprayed at Z3.1 stage were very good and show lower infection level than the checks (Tables
Effect of early fungicides sprays on scab severity, yield, infected kernel, and weight grains in 2007 season.
Treatments | Dose (g·ha−1) | Rust severity1 | Leaf bloth severity2 | Scab severity3 | Yield (t/ha−1) | Infected kernel (%) | Weight 1000 seeds (g) |
---|---|---|---|---|---|---|---|
Check | — | 8/25 | 6/50 | 15bc | 3.35cde | 5cd | 32.3a |
Check + inoculation | — | 8/25 | 6/50 | 80a | 2.32f | 48a | 25.6b |
Z31 trifloxystrobin + cyproconazole 267.5SC |
|
5/1 | 4/25 | 12bcd | 3.34cde | 6cd | 33.2a |
Z31 trifloxystrobin + cyproconazole 267.5SC + inoculation |
|
5/1 | 4/25 | 76a | 3.10de | 26b | 31.6a |
Z61 tebuconazole 25EW | 187.5 | 5/1 | 6/50 | 5cd | 3.82abc | 2cd | 34.3a |
Z61 prochloraz 45EC | 450 | 8/15 | 6/50 | 2d | 3.88ab | 0d | 33.9a |
Z61 metconazole 9SL | 90 | 8/15 | 6/50 | 6bcd | 3.94a | 3cd | 33.8a |
Z61 tebuconazole 25EW + inoculation | 187.5 | 8/15 | 6/50 | 18b | 3.66abc | 5cd | 34.5a |
Z61 prochloraz 45EC + inoculation | 450 | 8/15 | 6/50 | 10bc | 3.72abc | 5cd | 33.7a |
Z61 metconazole 9SL + inoculation | 90 | 8/15 | 6/50 | 12bcd | 3.76abc | 4cd | 32.9a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 tebuconazole 25EW |
|
5/1 | 4/5 | 2d | 3.95a | 4cd | 33.9a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 prochloraz 45EC |
|
5/1 | 4/5 | 0d | 3.92a | 3cd | 34.6a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 metconazole 9SL |
|
5/1 | 4/5 | 1d | 4.02a | 2cd | 34.9a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 tebuconazole 25EW + inoculation |
|
5/1 | 4/5 | 12bcd | 3.68abc | 6cd | 33.2a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 prochloraz 45EC + inoculation |
|
5/1 | 4/5 | 10bcd | 3.75abc | 6cd | 33.2a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 metconazole 9SL + inoculation |
|
5/1 | 4/5 | 10bcd | 3.79abc | 4cd | 32.7a |
LSD ( |
10 | 0.55 | 6.5 | 3.8 |
Within a column, means followed by the same letter are not significantly different (
Effect of early fungicides sprays on scab severity, yield, infected kernel, and weight grains in 2008 season.
Treatments | Dose (g·ha−1) | Rust severity1 | Leaf bloth severity2 | Scab severity3 | Yield (t/ha) | Infected kernel (%) | Weight 1000 seeds (g) |
---|---|---|---|---|---|---|---|
Check | — | 7/5 | 4/5 | 10bc | 3.50abc | 2cd | 34.5a |
Check + inoculation | — | 7/5 | 4/5 | 50a | 3.05c | 25a | 29.6b |
Z31 trifloxystrobin + cyproconazole 267.5SC |
|
4/1 | 3/5 | 14b | 3.50abc | 2cd | 34.5a |
Z31 trifloxystrobin + cyproconazole 267.5SC + inoculation |
|
4/1 | 3/5 | 50a | 3.15bc | 14b | 29.8b |
Z61 tebuconazole 25EW | 187.5 | 4/1 | 3/5 | 2d | 3.90a | 0d | 35.5a |
Z61 prochloraz 45EC | 450 | 7/5 | 4/5 | 4bcd | 3.78a | 0d | 35.9a |
Z61 metconazole 9SL | 90 | 7/5 | 4/5 | 5bcd | 3.96a | 0d | 34.7a |
Z61 tebuconazole 25EW + inoculation | 187.5 | 7/5 | 4/5 | 15b | 3.86a | 6c | 35.5a |
Z61 prochloraz 45EC + inoculation | 450 | 7/5 | 4/5 | 15b | 3.92a | 6c | 34.9a |
Z61 metconazole 9SL + inoculation | 90 | 7/5 | 4/5 | 15b | 3.86a | 4cd | 34.1a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 tebuconazole 25EW |
|
4/1 | 3/5 | 0d | 3.99a | 1d | 36.9a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 prochloraz 45EC |
|
4/1 | 3/5 | 0d | 3.85a | 1d | 35.5a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 metconazole 9SL |
|
4/1 | 3/5 | 0d | 3.97a | 0d | 36.1a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 tebuconazole 25EW + inoculation |
|
4/1 | 3/5 | 14b | 3.78a | 4cd | 34.7a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 prochloraz 45EC + inoculation |
|
4/1 | 3/5 | 9bc | 3.93a | 4cd | 36.6a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 metconazole 9SL + inoculation |
|
4/1 | 3/5 | 9bc | 3.84a | 3cd | 36.7a |
LSD ( |
6 | 0.55 | 6 | 3.9 |
Within a column, means followed by the same letter are not significantly different (
Effect of early fungicides sprays on scab severity, yield, infected kernel, and weight grains in 2009 season.
Treatments | Dose (L/ha−1) | Rust severity1 | Leaf bloth severity2 | Scab severity3 | Yield (t/ha) | Infected kernel (%) | Weight 1000 seeds (g) |
---|---|---|---|---|---|---|---|
Check | — | 8/5 | 7/20 | 29b | 3.35bc | 16c | 32.3ab |
Check + inoculation | — | 8/5 | 7/20 | 75a | 2.59e | 62a | 29.6b |
Z31 trifloxystrobin + cyproconazole 267.5SC |
|
5/15 | 4/25 | 25b | 3.33bc | 14c | 35.5a |
Z31 trifloxystrobin + cyproconazole 267.5SC + inoculation |
|
5/15 | 4/25 | 69a | 3.20c | 36b | 29.5b |
Z61 tebuconazole 25EW | 187.5 | 5/15 | 7/20 | 1c | 3.98a | 0d | 35.4a |
Z61 prochloraz 45EC | 450 | 8/5 | 7/20 | 1c | 3.90ab | 0d | 34.9a |
Z61 metconazole 9SL | 90 | 8/5 | 7/20 | 2c | 4.10a | 2d | 36.1a |
Z61 tebuconazole 25EW + inoculation | 187.5 | 8/5 | 7/20 | 8c | 3.86ab | 4d | 35.0a |
Z61 prochloraz 45EC + inoculation | 450 | 8/5 | 7/20 | 8c | 3.79abc | 0d | 34.9a |
Z61 metconazole 9SL + inoculation | 90 | 8/5 | 7/20 | 10c | 3.91ab | 2d | 35.2a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 tebuconazole 25EW |
|
5/15 | 4/25 | 5c | 4.12a | 2d | 35.9a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 prochloraz 45EC |
|
5/15 | 4/25 | 5c | 4.15a | 1d | 36.1a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 metconazole 9SL |
|
5/15 | 4/25 | 1c | 4.20a | 0d | 35.8a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 tebuconazole 25EW + inoculation |
|
5/15 | 4/25 | 9c | 3.88ab | 1d | 36.2a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 prochloraz 45EC + inoculation |
|
5/15 | 4/25 | 9c | 3.93ab | 1d | 36.7a |
Z31 trifloxystrobin + cyproconazole 267.5SC + Z61 metconazole 9SL + inoculation |
|
5/15 | 4/25 | 10c | 3.99a | 2d | 35.9a |
LSD ( |
12 | 0.56 | 8 | 5.4 |
Within a column, means followed by the same letter are not significantly different (
During 2007 and 2009 seasons, scab severity was high (Tables
The combined effects of a high level of foliar diseases infection and scab caused significant yield decrease, high infection in kernels, and noticeable reduction in weight. Nevertheless, spraying in full flowering stage with tebuconazole, prochloraz, or metconazole gives high head protection against
Fungicide sprayings at Z3.1 and Z6.1 stages reduced foliar disease and scab severity to the minimum and show the best results in yields. Higher yields and lower infection in kernels were found in laboratory tests, although these results did not significantly surpassed the sprayed treated checks at Z6.1. The additive effect of foliar diseases (
During the 2008 season, scab severity was light due to less favorable environmental conditions. In this season scab infections that observed any inoculated and uninoculated control were lower than the 2007 and 2009 seasons. Treatments with fungicides sprayed in Z3.1 plus Z6.1 stages showed no symptoms of the disease in the field. No significant differences were registered in performance between treatments inoculated or not with fungicides sprayed on any Z3.1 and Z6.1 stages. All these treatments overcome the yields observed with fungicide sprayed at Z3.1 stage and the checks with or without inoculations. A similar relationship was observed when analyzed % infected kernels and weight of the seeds.
Based on field trials carried out over three consecutive years, fungicide spray at Z3.1 stage did not reduce significantly head blight infection and grain weight however heavily reduce the percentage of infected kernels.
On natural infections there was no difference between spray and not spray with fungicide at Z3.1 stage for all scab parameters analyzed.
When scab was severity in 2007 and 2009 seasons, early fungicide spray at Z3.1 stage improved an increase in yields of an average of 22%, while a decrease kernel infection of an average of 40% compared with the inoculated check.
Twice fungicide applications at Z3.1 and Z6.1 stages reduced foliar disease and scab severity to the minimum and show that yields increase reaching average values of 55.3%, in comparison with the inoculated check and 19.6% with the uninoculated check.
When scab was light in 2008 season, no significant differences were registered in performance between treatments inoculated or not with fungicides sprayed on any Z3.1 and Z6.1 stages. These treatments overcome the yields registered with fungicide sprayed at Z3.1 stage and the checks with or without inoculations.