Whiteness
White stalk , also called rapeseed cancer or sclerotinia, is a plant disease caused by the fungus Sclerotinia sclerotiorum . It can attack various cultivated and wild plant species, but it only causes significant economic damage in rapeseed fields .
The importance of the white stalk in rapeseed cultivation is greater in northern Germany than in southern Germany . As a rule, the stems of infested plants fade after flowering without any sharp demarcation from healthy tissue. The infested zone, usually starting from a branch or a leaf attachment point, turns white, the bark is detached from the stem like a ram and the parts of the plant above the infested area die off. Often the stem kinks in this white area. In the inside of the stem, one initially finds white mycelium densities, which later change into black, irregularly shaped permanent bodies ( sclerotia ). When threshing , they return to the ground, where they remain infectious for several years. The infection of the sclerotinia is very dependent on the weather: Warm, humid sections before flowering promote the formation of apothecia (fruiting bodies) from the sclerotia . The alternation of showers and sun during flowering allows the spores flung out of the apothecia to germinate in the leaf and branch axils if the fallen petals adhere as a source of nutrients.
Combat
Fighting sclerotinia requires a greater gap in the crop rotation for oilseed rape and avoiding the cultivation of other host plants ( peas , sunflowers , potatoes ). The fungus can also multiply on weeds , so they must be controlled in the entire crop rotation. The targeted control with officially recognized fungicides against this disease has so far been based on the development stage of full bloom . A treatment appointment at the beginning of the infestation as with cereal diseases is not possible with this disease.
In biological pest control , the hyperparasitic fungus Coniothyrium minitans is successfully used against Sclerotinia scelotiorum . The application also minimizes the infection potential of sclerotia via the root system of damaging the oilseed rape, as C. minitans is washed in with the precipitation or carried into the soil as inoculum as long as sclerotia are present in the soil.
Individual evidence
- ↑ Turner, GJ and HT Tribe: On Coniothyrium minitans and its parasitism of Sclerotinia species . Ed .: Transactions of the British Mycological Society. No. 66 , 1976, pp. 97-105 .
- ↑ Jones, EE, A. Stewart and JM Whipps: Water potential affects Coniothyrium minitans growth, germination and parasitism of Sclerotinia sclerotiorum . Ed .: Fungal Biology. No. 115 , 2011, p. 871-881 .