Major fungicides used during the period

During the relevant period major changes in the use of actual fungicides have taken place.

This has happened due to the development of new products as well as to development of fun-gicide resistance. Table 6.1 shows the development in the sale of the most important fungi-cides (active ingredients) used in winter wheat crops. The specific fungifungi-cides mainly used in practical winter wheat production are shown in Table 6.2.

6.1.1 General level of response to fungicides

In order to assess if there have been major changes in yield response to fungicides obtained in the many field trials carried out over the years (including variety trials), data from trials at the Danish Agricultural Advisory Service (DAAS) and the Faculty of Agricultural Sciences (DJF) at Aarhus University have been collected in Figure 6.1. The trials have been sprayed with authorized products using a total of 50-100 per cent of the normal standard dose. The annual average indicates major differences between years. The annual variation is due to dif-ferent disease pressures influenced mainly by differences in climatic conditions, but varieties and fungicides used in the trials also play a major role. From 1971 to 1980 relatively few fun-gicides and trials were available, and yield increases in the range of 3-4 dt/ha were common using products like Maneb, Bayleton and Benlate. From 1981 when more effective and broad-spectrum fungicides were introduced, the yield increases rose by approximately 6 dt/ha.The data do not indicate a major change in response to fungicides since 1980 (Figure 6.1). The high yield response in the 1980s is highly influenced by severe yellow rust attacks in the later part of the 1980s and 1990 and very high Septoria levels in 1987 (Figure 6.1). Since 1990 especially Septoria has been dominant in the trials. Part of the high responses between 1998 and 2003 is also expected to be related to the introduction of the strobilurins in that period.

1980 1985 1990 1995 2000 2005 2010

Yield response to fungicide [dt/ha]

0 5 10 15 20 25

Figure 6.1Differences in yield response to fungicides (gross yield, dt/ha) in winter wheat crops in individual years (1981-2008) based on a large number of trials carried out by DAAS (The National Field Trials) and DJF.

6.2 Development of effectiveness and yield responses from fungicides

6.2.1 Major fungicides used during the period

During the relevant period major changes in the use of actual fungicides have taken place.

This has happened due to the development of new products as well as to development of fun-gicide resistance. Table 6.1 shows the development in the sale of the most important fungi-cides (active ingredients) used in winter wheat crops. The specific fungifungi-cides mainly used in practical winter wheat production are shown in Table 6.2.

Table 6.1 Sale (tonnes active ingredients) of the most important fungicides used in winter wheat crops (Miljøstyrelsen -pesticide statistics). A dash (-) indicates that the product was sold but the amount is not published.

Active ingredient 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

triadimenol/fon - - 9.2 18.1 36.4 42.0 22.5 12.5 7.7 6.7 0 prochloraz - - 104.6 170.3 157.4 94.1 90.7 57.1 26.9 27.3 29.4 fenpropimorph - 155.5 223.2 328.4 366.1 339.5 365.2 332.3 317.8 286.6 196.5 propiconazole - - 78.2 100.4 108.1 114.9 109.5 88.7 84.4 98.0 67.4 Active

ingredi-ent

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

prochloraz 16.5 11.7 3.7 1.8 10.3 0.4 0.8 1.0 1.8 0 0

propiconazole 86.6 46.0 24.9 29.8 22.1 19.1 17.0 29.5 30.9 24.5 8.3 fenpropimorph 278.5 219.3 132.9 118.6 104.2 87.4 76.3 25.6 16.2 23.1 17.8

fenpropidin 7.3 39.7 5.2 11.7 0 18.6 93.0 67.8 29.9 22.8

tebuconazole 3.7 26.9 19.6 46.2 55.0 52.1 32.1 30.6 26.2 21.8 20.4 azoxystrobin 71.3 93.5 69.3 77.2 55.6 35.9 23.2 26.8 22.4 21.9

kresoximmethyl 22.8 2.2 3.2 0.7 0.8 0.9 0.7 0.5 0

pyraclostrobin 33.575 43.0 41.8 23.8 17.9 12.1

epoxiconazole 20.7 37.6 46.6 42.4 41.0

boscalid 8.9 18.8

prothioconazole 7.4 12.8

Table 6.2 The fungicides most used in winter wheat since 1970.

Year Fungicides most used in winter wheat

1971-1980 Benlate (benomyl), Bayleton (triadimefon), Maneb 1981-1997 Tilt 250ec, Tilt turbo/ Tilt top (propiconazole)

1998 Amistar (azoxystrobin)

1999 Amistar (azoxystrobin), Mentor (kresoximmethyl) 2000 Amistar (azoxystrobin), Folicur (tebuconazole) 2001 Amistar (azoxystrobin), Folicur (tebuconazole)

2002 Comet (pyraclostrobin), Folicur (tebuconazole), (Amistar (azoxystrobin)) 2003 Comet (pyraclostrobin), Opus (epoxiconazole)

2004 Comet (pyraclostrobin), Opus (epoxiconazole). Recommended decreased amount of Comet

2005 Opus (epoxiconazole), (Comet (pyraclostrobin)) 2006 Opus (epoxiconazole), (Proline (prothioconazole))

2007 Opus (epoxiconazole), Bell (epoxiconazole + boscalid), Proline (prothioconazole)

Benzimidazoles (MBC) have been widely used in Denmark since the 1970s, and from the beginning of the 1980s, 65-80% of the winter cereal area was treated with these fungicides.

The largest quantities were used for control of eyespot in cereals (Oculimacula yallundae and O. cuformis) and snow mould (Michrodochium nivale) in winter cereals. In the early and mid-1980s unacceptable control levels were found under field conditions, and laboratory tests showed widespread resistance on isolates from O. yallundae, O. acuformis, and M. nivale.

The percentage of control of eyespot went from 80% in 1981 to 10% in 1984 (Jørgensen &

Table 6.1 Sale (tonnes active ingredients) of the most important fungicides used in winter wheat crops (Miljøstyrelsen -pesticide statistics). A dash (-) indicates that the product was sold but the amount is not published.

Active ingredient 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996

triadimenol/fon - - 9.2 18.1 36.4 42.0 22.5 12.5 7.7 6.7 0 prochloraz - - 104.6 170.3 157.4 94.1 90.7 57.1 26.9 27.3 29.4 fenpropimorph - 155.5 223.2 328.4 366.1 339.5 365.2 332.3 317.8 286.6 196.5 propiconazole - - 78.2 100.4 108.1 114.9 109.5 88.7 84.4 98.0 67.4 Active

ingredi-ent

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

prochloraz 16.5 11.7 3.7 1.8 10.3 0.4 0.8 1.0 1.8 0 0

propiconazole 86.6 46.0 24.9 29.8 22.1 19.1 17.0 29.5 30.9 24.5 8.3 fenpropimorph 278.5 219.3 132.9 118.6 104.2 87.4 76.3 25.6 16.2 23.1 17.8

fenpropidin 7.3 39.7 5.2 11.7 0 18.6 93.0 67.8 29.9 22.8

tebuconazole 3.7 26.9 19.6 46.2 55.0 52.1 32.1 30.6 26.2 21.8 20.4 azoxystrobin 71.3 93.5 69.3 77.2 55.6 35.9 23.2 26.8 22.4 21.9

kresoximmethyl 22.8 2.2 3.2 0.7 0.8 0.9 0.7 0.5 0

pyraclostrobin 33.575 43.0 41.8 23.8 17.9 12.1

epoxiconazole 20.7 37.6 46.6 42.4 41.0

boscalid 8.9 18.8

prothioconazole 7.4 12.8

Table 6.2 The fungicides most used in winter wheat since 1970.

Year Fungicides most used in winter wheat

1971-1980 Benlate (benomyl), Bayleton (triadimefon), Maneb 1981-1997 Tilt 250ec, Tilt turbo/ Tilt top (propiconazole)

1998 Amistar (azoxystrobin)

1999 Amistar (azoxystrobin), Mentor (kresoximmethyl) 2000 Amistar (azoxystrobin), Folicur (tebuconazole) 2001 Amistar (azoxystrobin), Folicur (tebuconazole)

2002 Comet (pyraclostrobin), Folicur (tebuconazole), (Amistar (azoxystrobin)) 2003 Comet (pyraclostrobin), Opus (epoxiconazole)

2004 Comet (pyraclostrobin), Opus (epoxiconazole). Recommended decreased amount of Comet

2005 Opus (epoxiconazole), (Comet (pyraclostrobin)) 2006 Opus (epoxiconazole), (Proline (prothioconazole))

2007 Opus (epoxiconazole), Bell (epoxiconazole + boscalid), Proline (prothioconazole)

Benzimidazoles (MBC) have been widely used in Denmark since the 1970s, and from the beginning of the 1980s, 65-80% of the winter cereal area was treated with these fungicides.

The largest quantities were used for control of eyespot in cereals (Oculimacula yallundae and O. cuformis) and snow mould (Michrodochium nivale) in winter cereals. In the early and mid-1980s unacceptable control levels were found under field conditions, and laboratory tests showed widespread resistance on isolates from O. yallundae, O. acuformis, and M. nivale.

The percentage of control of eyespot went from 80% in 1981 to 10% in 1984 (Jørgensen &

Thygesen, 2006). By 1986 the biological approval for single products as well as mixtures with benzimidazoles was withdrawn for eyespot in cereals, and labels were amended. As a conse-quence a dramatic drop in the treated area of winter cereals with these products took place.

Triazoles have generally given very cost-effective control of major cereal diseases for more than 25 years in Denmark. The use of triazoles increased significantly during the 1980s, and for many years propiconazole was the dominant active ingredient used for disease control in cereals. When first authorized, most of the triazoles were approved for control of powdery mildew in cereals in general. Today this efficacy is regarded as being relatively low with the exception of tebuconazole (Jørgensen & Thygesen, 2006).

The level of control of Septoria leaf blotch has been assessed in field trials since the begin-ning of the 1990s using two treatments with 1/3 of the full label rate of propiconazole. Over-all, there has been a significant drop in efficacy, although annual variations should be noted.

Epoxiconazole has only been authorized in Denmark since 2003 and prothioconazole since 2006. These two fungicides still provide effective control and yield responses, although a drop in efficacy from reduced rates of epoxiconazole have taken place since 2004.

Strobilurins were introduced in Denmark in 1998, and soon afterwards resistance to powdery mildew (Blumeria graminis f.sp. tritici) was found in wheat, which led to the amendment of the label recommendation. From spring 2003 to summer 2004 the level of G143A mutations in Septoria leaf blotch (Mycosphaerella tritici) in Denmark increased from 2.5% to 81% (Jør-gensen & Thygesen, 2006). A similarly rapid development was found in many neighbouring countries. The significant yield benefit from the strobilurins found in relation to the newer triazoles had disappeared in wheat by 2004.

The major trend in fungicide use since 1990 in Figure 6.2 is expressed by the development in Treatment Frequency Index (TFI; regarding fungicides synonymously to Total Fungicide In-put which is used occasionally) in use of triazoles (propiconazole, tebuconazole, epoxicona-zole, etc.) and strobilurins (kresoxim-methyl, azoxystrobin, pyraclostrobin). Treatment Fre-quency Index is defined as the number of standard doses used. Fungicides containing triazoles have been the major group used during the last 25 years.

Thygesen, 2006). By 1986 the biological approval for single products as well as mixtures with benzimidazoles was withdrawn for eyespot in cereals, and labels were amended. As a conse-quence a dramatic drop in the treated area of winter cereals with these products took place.

Triazoles have generally given very cost-effective control of major cereal diseases for more than 25 years in Denmark. The use of triazoles increased significantly during the 1980s, and for many years propiconazole was the dominant active ingredient used for disease control in cereals. When first authorized, most of the triazoles were approved for control of powdery mildew in cereals in general. Today this efficacy is regarded as being relatively low with the exception of tebuconazole (Jørgensen & Thygesen, 2006).

The level of control of Septoria leaf blotch has been assessed in field trials since the begin-ning of the 1990s using two treatments with 1/3 of the full label rate of propiconazole. Over-all, there has been a significant drop in efficacy, although annual variations should be noted.

Epoxiconazole has only been authorized in Denmark since 2003 and prothioconazole since 2006. These two fungicides still provide effective control and yield responses, although a drop in efficacy from reduced rates of epoxiconazole have taken place since 2004.

Strobilurins were introduced in Denmark in 1998, and soon afterwards resistance to powdery mildew (Blumeria graminis f.sp. tritici) was found in wheat, which led to the amendment of the label recommendation. From spring 2003 to summer 2004 the level of G143A mutations in Septoria leaf blotch (Mycosphaerella tritici) in Denmark increased from 2.5% to 81% (Jør-gensen & Thygesen, 2006). A similarly rapid development was found in many neighbouring countries. The significant yield benefit from the strobilurins found in relation to the newer triazoles had disappeared in wheat by 2004.

The major trend in fungicide use since 1990 in Figure 6.2 is expressed by the development in Treatment Frequency Index (TFI; regarding fungicides synonymously to Total Fungicide In-put which is used occasionally) in use of triazoles (propiconazole, tebuconazole, epoxicona-zole, etc.) and strobilurins (kresoxim-methyl, azoxystrobin, pyraclostrobin). Treatment Fre-quency Index is defined as the number of standard doses used. Fungicides containing triazoles have been the major group used during the last 25 years.

1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

Treatment Frequency Index

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0

Strobilurins Triazoles

Figure 6.2Treatment Frequency Index (TFI) for triazoles (plus mixtures with morpholines before 1998) and strobilurins measured in winter cereal (Miljøstyrelsen - Pesticide statistic).

In document summary Causes of yield stagnation in winter wheat in denmark (Sider 78-81)