6       January 2005        The CRS CommPoster

 

 

 

 

 

Yes. We do Have a Choice:                      

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pathogen enzymes that are necessary for virulent functions in pathogens. Copper compounds, such as Mancozeb (Dithane-45), Zineb (Dithane Z-78), Manzate, Captan, Folpet, Daconil, Bravo, etc. damage a number of fungal enzymes and functions. These act as Broad-spectrum fungicides and offer control against a number of different types of fungi.  Since Multisite fungicides act on a number of physiological activities, it is almost impossible for fungal pathogens to develop fungicide resistance.  Multisite fungicides are toxic to a number of host functions, and so phytotoxic

 

Multisite surface protectants such as Deconil, Bordeaux mixture, or sulfur act on the surface only, and do not enter the plant cell.  These fungicides, therefore, must be on the foliar surface before the fungus arrives on the scene. Once the fungus establishes itself within the plant, these can offer no control

 

For effective control, use Multisite and single site fungicides either in combination or alternatively.   Use of broad-spectrum fungicide along with single site fungicide will decrease the formation of resistant mutants.   It is best to alternate a systemic fungicide with one of the Surface Protectant fungicides to prevent the formation of fungicide resistant mutants. Propiconazole, thiophanate-methyl, triforine are systemic fungicides. Systemic fungicides get translocated to other parts of plant and offer better protection.

 

Use of less toxic fungicides:

Antitranspirants (AT) as Non-Toxic Fungicides: Antitranspirants such as plant waxes, polyterpenes, silicones, latex compounds, acrylic esters or high molecular weight alchohols do not kill pathogens, but offer protective control over fungal penetration. At high concentrations and

elevated temperatures (hot dry summers) antitranspirants may be phytotoxic. 

 

 

Antitranspirants may reduce photosynthesis.  Antitranspirants are biodegradable, non-toxic, and cheaper than other fungicides

 

Sodium bicarbonate (baking soda) as fungicide:

Cornell University scientists demonstrated significant control of powdery mildew and black spot by weekly spraying of 0.063M aqueous solution of baking soda.  Baking soda and horticultural oil are synergistic in their ability to control fungal pathogen.   Effectiveness of control is attributed to fungicidal properties of bicarbonate ions, fungicidal, and spreader sticky characteristics of oil that keep the bicarbonate ions on the foliar surface.  Baking soda inhibits the germination of fungal spores.  As biocontrol agent, it is effective only when the inoculum is low.   The term fungicide is often used rather loosely.  Most fungicides do not kill fungi, rather inhibit their growth.  Baking soda is fungistatic. (Strictly speaking, a fungicide should kill fungi.  When a control agent checks only fungal growth, it is fungistatic).  At high temperatures, horticultural oil may be phytotoxic.

Neem oil based products are potent killers of pathogenic fungi, bacteria, and insects and do not poison the environment.   Another popular product in the European market for control of black spot, powdery mildew and a variety of other fungal diseases is soluble silicon.  Soluble silicon is available as metasilicate.   Foliar application of metasilicate, in addition to controlling fungal diseases appears to enhance flower production.    Because of silicon accumulation in leaf cells, leaves get harder and stand erect creating a physical barrier between the pathogen and the host.   Soluble silicon is commercially available as ZACSIL. 

Microorganisms for control of microbial

 

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