Take‐all and grain yields in sequences of winter wheat crops testing fluquinconazole seed treatment applied in different combinations of years

Abstract

A seed treatment containing fluquinconazole as the only active ingredient was tested in sequences of up to six consecutive crops of winter wheat. It was applied or not applied in each year, and was tested in all possible combinations with treatments applied in previous years. Take-all was controlled effectively, and grain yield usually increased, when the disease intensity was moderate or severe in non-treated crops, but control of the most severe take-all did not result in acceptable yields or grain quality. Treatment of a first wheat or second wheat with little take-all did not usually benefit the subsequent crop. Non-treatment of a crop grown after a treated, diseased crop usually resulted in a marked increase in disease, indicating that treatment had delayed progress of the epidemic. Take-all was controlled by treatment of a crop grown after a treated, diseased crop but the amount of control and of increased yield was often less than that in a treated crop grown after a non-treated crop in the same crop sequence. Similar effects of seed treatment were apparent in crops grown on a site with take-all decline. The alternative fungicide, silthiofam, applied as a seed treatment in the later years of some experiments, was usually as effective as fluquinconazole. From these experiments, it is recommended that: a) fluquinconazole seed treatment should be applied to a second or third wheat crop, grown after a first wheat crop that was managed to avoid rapid take-all development (e.g. by avoiding very early sowing); b) a break crop should follow the treated crop; c) the seed treatment should not normally be used in longer sequences of wheat or on take-all decline soil unless it is planned to follow the treated crop with a non-cereal break.

Methods for studying population structure, including sensitivity to the fungicide silthiofam, of the cereal take‐all fungus, Gaeumannomyces graminis var. tritici

“…Fluquinconazole did not have any significant effect on the population structure of Ggt , measured by the percentage of the T2 mtSSU rRNA gene RFLP type, or the percentage of ITS4/ITS5 Hpa II B‐type, over 3 years (Bateman et al ., 2003; Freeman, 2004). Research has shown that fluquinconazole can be applied with economic effect on second or third wheat crops, but that a treated diseased crop should be followed by a break crop (or the following crop should be treated), and that treatment should not be applied during long sequences of wheat crops as it may disrupt development of the year‐to‐year epidemic and possibly take‐all decline (Bateman et al ., 2003, 2004).…”

“…Take‐all disease and soil infectivity data are shown only for experiment CS/323, in which comparisons between nontreated and silthiofam‐treated crops are made. Other take‐all data from the experiments are presented elsewhere (Bateman et al ., 2003, 2004). The plant sample to assess take‐all was taken in early July 2002 at growth stage 73 (Zadoks et al ., 1974).…”

“…However, insensitivity to silthiofam occurs naturally in Ggt populations that have never been exposed to the fungicide, and there is variation in the level of this insensitivity (Russell et al ., 2001; Carter et al ., 2003; Lebreton et al ., 2003; G.L.B., unpublished data). Research in this area is currently hampered, in the same way as the population monitoring done so far (Bateman et al ., 1997, 2003), by the need to isolate large numbers of isolates from populations of Ggt in soil or on cereal roots to determine the overall level of insensitivity, and any changes in sensitivity that may occur naturally within or between cropping seasons or as a consequence of fungicide use.…”

Effects of different cultivated or weed grasses, grown as pure stands or in combination with wheat, on take‐all and its suppression in subsequent wheat crops

“…The number and percentage of diseased root axes were determined on plants sampled in March. Those sampled in July were scored for take‐all as follows (Bateman et al ., 2004): 1, slight disease with 1–10% of root system affected; 2, slight disease, 11–25% affected; 3, moderate disease, 26–50% affected; 4, moderate disease, 51–75% affected; 5, severe disease, 75% of root system affected. A take‐all index (TAI: 0–100) was calculated as the sum of the percentage of plants in each score category multiplied by its score value, divided by five.…”

Management of resident plant growth-promoting rhizobacteria with the cropping system: a review of experience in the US Pacific Northwest

“…Metalaxyl (Apron®) is the dominant product used for control of Pythium on germinating seeds, used in combination with either difenoconozole (Dividend®) or tebuconazole (Raxel®) for control of smuts (Smiley et al 1996). No work has been done in the Pacific Northwest with the seed treatment product fluquinoconazole, shown in Europe to have some benefit against take-all (Bateman et al 2004), but results from seed-treatment trails conducted with silthiofam, registered in Europe as Latitude® (Beale et al 1998) and shown to provide some level of take-all control used as seed treatment (Bailey et al 2005), has shown no benefit in the Pacific Northwest beyond the combination of agricultural practices described above (Cook, unpublished). In contrast, treatment of seeds with metalaxyl combined with either difenoconozole or tebuconazole produced average yield increases of 4-5% in continuous direct-seeded winter and spring wheat using the best agricultural practices described above .…”