Winter oilseed rape: Evaluation of fungicide spray programmes
About this project
A series of six replicated plot scale trials was done in 1990/91 to evaluate the effect of differently timed single and multiple sprays of prochloraz (Sportak) and iprodione plus thiophanate-methyl (Compass) on disease control and yield of winter oilseed rape.
The sites were Fonmon (S Glamorgan), Hawkinge (Kent), High Mowthorpe EHF (N Yorks), Neston (Wilts), Terrington EHF (Norfolk), and Threekingham (Lincs).
Fungicides were applied as either:
(a) Single sprays of Sportak (1.25 l/ha) at the following timings: autumn, mid-February, mid-March, early stem extension, early-mid flowering, and end of flowering.
(b) Two-spray programmes; Sportak in the autumn plus at early stem extension, or, Sportak at early stem extension plus Compass (3.0 l/ha) at the end of flowering.
(c) A 3-spray programme of Sportak at autumn and early stem extension plus Compass at the end of flowering.
Disease levels were low to moderate at most sites with significant pod invasion occurring only at Neston and Threekingham.
Light leaf spot (Cylindrosporium concentricum, perfect stage Pyrenopeziza brassicae) was the most common disease encountered. Control of this disease was significant (p = 0.05) in the spring with autumn and early spring applications at High Mowthorpe and Neston.
Phoma leaf spot (Phoma lingam, perfect stage Leptosphaeria maculans) developed at low levels at all sites except Fonmon. Disease incidence was significantly (p = 0.05) reduced at Neston (early flowering assessment) by single sprays applied at mid-March and early stem extension, and by the autumn plus stem extension programme. Stem canker developed to moderate levels at Hawkinge and Neston with very low levels at High Mowthorpe. Both programmes with an autumn plus stem extension spray gave good reduction in disease severity at Hawkinge, but so did single sprays applied in mid-February and mid-March with the latter being the best treatment. At Neston, the incidence of stem canker was significantly (p = 0.05) reduced by all of the spray programmes, as well as the mid-February, mid- March,and stem extension sprays, but again, the mid-March spray was the best treatment.
Sclerotinia (Sclerotinia sclerotiorum), a rarity in most seasons, was found, albeit at low levels, at High Mowthorpe, Neston and Threekingham. Alternaria pod spot (Alternaria brassicae and Alternaria brassicicola) was found at trace levels at Neston, and moderate levels at Threekingham. End-of-flowering sprays of Sportak or Compass gave significant control of pod spot at Threekingham. Ringspot (Mycosphaerella brassicicola) affected the pods quite severely at Neston, but no treatment gave significant reduction in disease levels. The mean untreated yield from the six sites was 2.95 t/ha. Significant (p = 0.05) yield increases were obtained at two sites; at High Mowthorpe from sprays applied in mid- February, mid-March and early flowering and from all of the spray programmes. At this site the biggest response was from the 3-spray programme. At Neston, significant responses were obtained from both spray programmes that included an end of flowering spray of Compass. Positive responses were obtained at four sites. There was however no obvious relationship between disease control and yield. At individual sites very few treatments would have been profitable if the value of the seed was £130/t. At £240/t the most economic timing (meaned across the sites) would be the mid-March application.
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