By Yeshi Wamishe, Extension Rice Pathologist
Disease occurs when a virulent pathogen, a susceptible host and favorable environment are in perfect alignment. In the absence of one of the three factors, the chance for disease to occur is none. No rice field is clean of all diseases. It’s safe to assume there is always a virulent pathogen capable of causing a particular disease in a field. However, if your variety is resistant, it will not be overwhelmed by the disease depending on the resistance type and level. Likewise, if you make the conditions favorable for your crop and unfavorable for the pathogen using your best cultural practices, you make a disease fully or partially fail to develop or progress.
As the name implies, fungicides act on fungi and have nothing to do with your variety or the environment. Fungicides are used to suppress the pathogen’s growth and development. Applying a fungicide in the absence of disease is an abuse on its long-term effectiveness, i.e., the target pathogen may develop insensitivity to the product. Fungicides are to be used only when needed either as protective or to suppress the disease. Therefore, an integrated approach (selecting resistant cultivars, practicing the best field management and applying a fungicide when needed) is the most beneficial rice disease management strategy.
Remember the following tips:
- Refer to fungicide labels. Labels are the rule.
- Avoid automatic fungicide application. Fungicides are only to kill or suppress fungi.
- Fungicides benefit in well managed fields if applied correctly at recommended timings, rates and frequency using adequate volume of water for coverage.
- Scout for some diseases such as sheath blight and blast to make your best economic decision.
- If tank mixing, mixes need to be checked for compatibility.
- Regardless of a few choices for rice, it is advised to rotate chemistries that have different modes of action to delay pathogens from developing fungicide resistance.
- Remember any fungicide does not kill all fungi. i.e., specific fungicides are required for specific fungi. Blast and sheath blight, however, are managed by similar chemistry (commonly the strobilurins). More choices are available for sheath blight than blast.
- Instead of expensive premix fungicides, generic forms can be mixed to cut cost. Make sure rates are as recommended. For instance you can make 21 oz of QuiltXcel by mixing 12 oz of Quadris with 6 oz of Tilt. More rated are shown below:
10.5 oz QuiltXcel = 6.0 oz Quadris + 3.0 oz Tilt
14.0 oz QuiltXcel = 8.0 oz Quadris + 4.0 oz Tilt
15.75 oz QuiltXcel = 9.0 oz Quadris + 4.5 oz Tilt
17.5 oz QuiltXcel = 10.0 oz Quadris + 5.0 oz Tilt
21.0 oz QuiltXcel = 12.0 oz Quadris + 6.0 oz Tilt
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