Canola Essay

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Evaluation of Fungicide Control of Sclerotinia Stem Rot on Canola (SSR)
Yin Chen
Description of disease affecting crop
Sclerotinia stem rot (SSR) is caused by fungus named sclerotinia sclerotiorum (Lib.) de Bary. It is a common disease in oilseed rape (Brassica napus) field. In Sweden, S. sclerotiorum can cause 60% yield reduction in infected fields (Nordin, 1992). SSR is a major disease of canola in North Dakota. The incidence ranged from 7-19% in North Dakota from 1991 to 1993. ( Lamey, 1995). It occurs almost every year and in most regions of the state. Symptoms on canola appear when flowering appear two to three weeks after infection. Mushy is the first visible symptom. Petals are the first part to be infected, then infection can spread to leaf petioles and finally to stems. Light brown discoloured patches will show on stems, branches and pods. These lesions will expand and the plant surface becomes greyish-white color. When main stem is infected, the canola plant will be easy to lodging. Hard, black structures called sclerotia (survival structure of the pathogen) will be produced on infected tissues after the infection is well-established. It can be found inside of infected stem.
Pathogens-including disease cycles
The fungus sclerotinia sclerotiorum over winters as sclerotia either in the soil or in stubble at the soil surface (Morton and Hall, 1989). If the weather (moisture and temperature) is favorable, small mushroom-like structures called apothecia will be produced on the sclerotia. Each sclerotia can several apothecia. Apothecia can produce millions of spores called ascospores. Ascospores will be released in air when the apothecia is mature. Some ascospores land on canola plants and infect dead canola tissues like fal...

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...nts. In addition, air treatment has no effect on disease control.
Discussion
This practice is not recommended. There are three reasons. First of all, air treatment is not effective at all. There is no data can show if the air treatment can effectively remove the senesced flowers from the maturing plants and it is unclear if remove senesced flower has unstable effect on disease control. Even if the fungicides were applied, the yield and plant weight did not increase and the disease incidence and severity sometimes higher than untreated control on fungicide treated plants.
Additional information needed
The recommended application rate of each fungicide and if the air treatment really can remove senesced flowers effectively.
Summary
This management practice is not recommend since it unlikely to control the sclerotinia stem rot in canola field or improve the yield.

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