Integrated disease management is the best approach to keep major rice diseases under control, i.e., varietal resistance, best cultural practices and chemical products.
Varietal resistance is the best and most user friendly disease control measure. However, host resistance is not always available to all diseases.
Cultural management strategies are beneficial to reduce some rice diseases. However, at times yield potential may be compromised.
Routine fungicide application may be practiced, but it increases the likelihood of fungicide resistance and is rarely economically feasible. Besides, the available fungicides do not fully suppress/control the most prevalent diseases of rice.
Therefore, the integrated approach is inevitable. Fungicides work best in well-managed fields and in less susceptible varieties.
Tips to benefit the most from fungicide applications
• Fungicides applied at recommended timing and rate work best and maximize their benefit.
• Well-managed fields benefit better from fungicide application.
• Fungicides mixed in adequate volume of water provide better coverage, particularly to fungicides applied on foliage.
• If tank-mixing is required, check for the compatibility of the chemistries.
• To target more than one disease that require protective products, combination fungicides (Triazole + Strobi) work better (for instance, kernel smut, false smut and neck blast).
• To reduce resistance to fungicides, rotate chemistries with different modes of action.
• To cut expenses and also reduce resistance to fungicides, avoid automatic application. Apply fungicides when and where needed (scouting, previous knowledge of field history and variety resistance help to make the right decisions).
• To reduce fungicide cost, products with different modes of action can be tank-mixed by adjusting rates as required.
• To get maximum performance from fungicides, higher rates are usually preferred.
• Scouting for sheath blight in particular can help determine fungicide rate, timing and necessity.
Research by Dr. Rick Cartwright includes: Stratego at 16 oz provided 14-17 days control, whereas the 19 oz for 21-24 days. Quadris at 6.4 oz provided 10-14 days control while 9 oz for about 21 days. But the full rate 12.5 oz provided 28 days of control. Moreover, his research indicated Azoxystrobin (Quadris) to be somewhat more effective on sheath blight than Trifloxystrobin (GEM)–but the difference was just slight.
• To suppress minor leaf and sheath diseases, fungicide application may not be warranted. Broad spectrum fungicides such as strobilurins, if applied for major diseases such as sheath blight and blast, should provide control for minor diseases.
More information at the University of Arkansas' Management of Rice Disease.