Abstract
In Cameroon, Mycosphaerella fijiensis was reported for the first time in 1981 and the control against black leaf streak disease represents the highest production cost which can attend up to 10% of total production cost. In fact, the epidemiological context which exists in Cameroon is particularly favourable to the disease notably in the rainy season from April to November. Towards the end of the 80s, a forecasting system using biological descriptors was elaborated and applied with success, reducing the number of treatments to 12 - 14 per year. Since 1996, the development of fungicide resistance lead, even if the levels of resistance fluctuate, to the progressive abandon of this rational strategy at the expense of systematic control methods. Thus in 2005, about 40-50 treatments were done on most of the plantations and the control programme was based on the ratio of 80% of contact fungicides and 20% of systemic and penetrant fungicides. This evolution has lead to an important increase of the cost of disease control, but also to an increase of negative environmental effects. In those conditions, research conducted in Cameroon is aimed to: - Experiment fungicides having less negative environmental effects. - Adapt control strategies to the situation of fungicide resistance. Experiments realised in 2005 have shown that chlorothalonil enabled a very good control of the disease, even in the rainy season. New strategies where the proportion of chlorothalonil would be rationalized to a minimum are presently evaluated. - Evaluate the possible reversibility of fungicide resistance, in order to reintroduce a the more sustainable forecasting strategy. The hypothesis is that the fluctuations observed in the resistance frequency to systemic fungicides could result from a lower fitness of resistant strains, which could be counter- selected in the absence of the fungicide selection pressure and/or gene flow between the treated and the untreated areas. (Resume d'auteur)
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Claims 7
Claim · model-written summary
A forecasting system based on biological descriptors, applied with success, reduced the number of fungicide treatments to 12-14 per year.
- Treatment
- forecasting system using biological descriptorse0
- Outcome
- number of treatmentse0
- Direction
- reducinge0
- Value
- 12 - 14 per yeare0
Not reportedTaxonComparator
Verbatim
e0“a forecasting system using biological descriptors was elaborated and applied with success, reducing the number of treatments to 12 - 14 per year”
Claim · model-written summary
In 2005 about 40-50 treatments were applied on most plantations.
Not reportedTaxon
Verbatim
e1“in 2005, about 40-50 treatments were done on most of the plantations”
Claim · model-written summary
Since 1996, fungicide resistance development led to progressive abandonment of the forecasting-based rational strategy.
- Outcome
- progressive abandon of this rational strategye2
- Qualifier
- development of fungicide resistancee2
Not reportedTaxon
Verbatim
e2“Since 1996, the development of fungicide resistance lead, even if the levels of resistance fluctuate, to the progressive abandon of this rational strategy”
Claim · model-written summary
The shift to systematic control increased the cost of disease control substantially.
Not reportedTaxon
Verbatim
e3“important increase of the cost of disease control”
Claim · model-written summary
The shift to systematic control also increased negative environmental effects.
Not reportedTaxon
Verbatim
e4“an increase of negative environmental effects”
Claim · model-written summary
Experiments in 2005 showed that chlorothalonil gave very good control of the disease, even in the rainy season.
- Treatment
- chlorothalonile5
- Outcome
- control of the diseasee5
- Direction
- very goode5
- Qualifier
- even in the rainy seasone5
Not reportedTaxonComparator
Verbatim
e5“Experiments realised in 2005 have shown that chlorothalonil enabled a very good control of the disease, even in the rainy season”
Claim · model-written summary
The authors hypothesise that fluctuations in resistance frequency to systemic fungicides could result from lower fitness of resistant strains.
- Outcome
- fluctuations observed in the resistance frequency to systemic fungicidese6
- Qualifier
- lower fitness of resistant strainse6
Not reportedTaxon
Verbatim
e6“the fluctuations observed in the resistance frequency to systemic fungicides could result from a lower fitness of resistant strains”