DAMPING-OFF PLANT PATHOLOGY MAMOONA GHAFFAR
Contents : Introduction Causal agents Disease attacks to Life cycle Stages Symptoms Causes Control Management Other tips and suggestion
Introduction : Fungi usually just at the soil level on to hypocotyl or upper taproot causing partial or complete rot and the seedlings suddenly topple over in a characteristic manner. Of the various species of soil-inhabiting fungi responsible for damping-off of seedlings, Pythium debaryanum ranks first in importance, in relation to this disease as a damping-off parasite. FIRST STUDIED by : Hesse in 1874 De Bary in 1881
CAUSUAL AGENTS : A number of different fungi and fungi-like organisms cause the symptoms of damping off, including: Alternaria species. Cause leaf spotting. [2] Alternaria [2] Botrytis cinerea – also known as "grey mould". Symptoms caused by this often accompany other symptoms. [2] Botrytis cinerea [2] Fusarium species. [1] Fusarium [1] Macrophomina phaseoli – a plant pathogen that causes charcoal rot on many plant species including Zea mays and Pinus elliottii. [citation needed] Macrophomina phaseoliplant pathogenZea maysPinus elliottiicitation needed Phyllosticta species. Cause leaf spotting. [2] Phyllosticta [2] Phytophthora – a genus of plant-damaging oomycetes (water molds), whose member species are capable of causing enormous economic losses on crops worldwide, as well as environmental damage in natural ecosystems. [3] Phytophthoraoomyceteswater moldsecosystems [3] Pseudomonas species. Cause leaf spotting. [2] Pseudomonas [2] Pythium – a genus of parasitic oomycete. Once classified as fungi, and consequently sometimes still treated as such. Along with Rhizoctonia solani, attacks by Pythium are most associated with producing roughly circular patches of dead seedlings. [2] Pythiumparasitic [2] Rhizoctonia solani – a plant pathogenic fungus with a wide host range and worldwide distribution. [3] Rhizoctonia solani [3] Sclerotium rolfsii – a corticioid fungus in the family Atheliaceae. It is a facultative plant pathogen and is the causal agent of "southern blight" disease in crops. [4][5] Sclerotium rolfsiicorticioid fungusfamilyAtheliaceaefacultativecrops [4][5] Thielaviopsis – a small genus of fungi in the order Microascales. The genus includes several important agriculturalpathogens. [6][7] ThielaviopsisgenusorderMicroascalesagricultural [6][7]
Identification of Damping Off Disease Identification of this disease is easy. Seedlings, which were previously healthy, fall over. They do so, right at the soil level. You might not see the fungus at first. As the disease progresses, this white cottony fungus is clearly visible on top of the soil. As days, go by it, quickly worsens.
Disease attacks to : Almost any kind of plant may be attacked by damping-off fungi while in young, tender, succulent stage of development. But the disease incidence is dependent more upon the conditions under which the seedlings are grown than upon the particular species of plant concerned.
Damping-off of seedlings actually occurs in two stages:
SYMPTOMS : All symptoms result in the death of seedlings Circular patches Stem lesions at ground level Stem of seedling may also become thin and tough Leaf spotting Grey mold growth on stem and leaves Roots sometimes rot completely Discolored stumps Low rate of germination Seedlings to topple White/pink /grey cottony fungus
SYMPTOMS
Seedling To Topple
Stem lesion Circular patches Stem lesion at ground level Leaf spotting
CAUSES : Abundant moisture Fairly warm temperature Lack of aeration of the surface soil Too much shade Thick sowing in seed bed Water logging Soil temp 20`C – 28`C are ideal for host infection by direct penetration Enzymes secreted by pathogens 1. Pectinolytic 2. Proteolytic 3. Cellulolytic
CONTROL Since the fungus responsible for causing damping-off trouble is soil- borne and since the temperature and moisture factors of the environment play important role in determining the severity of infection, control measures are largely based on: (i) Proper seed bed soil preparation (ii) Soil treatment (iii) Seed treatment (iv) The manipulation of watering system (v) Application of improved cultural practices.
Controlling of damping-off disease Do ** Buy sterilized seed starting soil. ** Use clean, sterilized containers. ** Provide plenty of air circulation. Tip Use a small fan and direct a very gentle breeze across the plants. The important word here is "gentle", as seedlings are delicate. ** Thin seedlings to increase air circulation. ** Provide as much sunlight as possible. ** Let the surface of the soil dry out between watering. Watering from the bottom is much preferred. ** Stir the top of the soil around the seedlings. ** Put plants in a sunny location. It helps to keep the surface soil dry. Don’t ** Don't leave your seedling trays in the basement. Basements are perfect breeding grounds for molds and fungus.. ** Don't overwater plants. ** Do not use fertilizer on your new seedlings. ** Don't use tray covers. While it is a popular practice to use them, they increase the humidity level, and encourages disease growth.
Other Tips and Suggestions: It is believed that soaking seeds in a small amount of water and a clove of crushed garlic will prevent the disease. Some people suggest misting the plant with Chamomile tea as a preventative. Some people suggest fireplace ash on the top of the soil. Cinnamon also acts as a fungicide. Sphagnum moss spread thinly on the surface of the soil.
Thank you Regarding : Mamoona Ghafffar