Compositions and Rates of Fungicides for Major Rice Diseases

by Yeshi Wamishe, Extension Plant Pathologist - July 6, 2022

Some rice planting pulled towards the late end of the planting window again in 2022. Generally, late-planted rice may have more diseases than early-planted rice. In experimental CL163 plots at the Rice Research and Extension Center (RREC), sheath blight symptoms showed up within five days after artificial inoculation. The plots were planted with the maximum seeding rate and received nitrogen fertilization 30% above the recommended rate. Currently, the disease is progressing. This shows that both management and micro-environment matter for disease development. 

So far, there are not many reports on leaf blast. With kernel smut and false smut, it is difficult to scout for it because it is too late to do anything once the disease is detected. For late season blast and these two smuts, timely application of protective fungicides is essential. Triazoles applied at mid-boot may help to suppress Cercospora narrow brown leaf spot (NBLS) to some level. 

Fungicide applications are not warrented to suppress minor leaf and sheath diseases. You may supress them with a broad spectrum fungicide containing strobulurin, if applied to suppress sheath blight or blast.

Remember: Well managed fields benefit better from fungicide application. Fields benefit from fungicides applied at recommended timing and rate using an adequate volume of water. 5 to 7 gal/acre provides adequate coverage for areal applications and up to 10 gal/acre for ground applications. We have seen less fungicide benefit in rice fields that received fungicides with less than a 5 GPA rate water. Our three year research on sheath blight has shown that fungicides applied using a 3 GPA rate water were as bad as the unsprayed check.

Refer to Tables 1-5 below for information on the compositions of active ingredients and rates of commonly used fungicides in Arkansas rice.

Table 1. Fungicides for Major Rice Diseases

*Stratego may not be available for rice. GEM RC or Flint® (both Trifloxystrobin) may be used. For reference, GEM RC contains 42.6 % of Trifloxystrobin and Flint 50%.
**Elegia is in the same FRAC Code with Sercadis and helps prevent the spread of resistant sheath blight. There is no strong proof for the prevalence of resistant sheath blight fungus in Arkansas rice. However, rotating fungicides with different modes of action are recommended to delay resistance. When using Elegia, please use the maximum rate shown in the table above.

Table 2. Rates of Active Ingredients in Stratego

*If Stratego is available and to be used to suppress smuts, the 19 fl oz/acre rate has close to the recommended amount of Tilt for smuts. You may adjust the rates of triazoles as desired.

Note: The following information was exctracted based on assessment of the research from Dr. Rick Cartwright. Stratego at 16 oz provided 14 to 17 days control for sheath blight, whereas the 19 oz for 21-24 days.  

Table 3. Rates of Active Ingredients in Quilt Xcel (Q Xcel)

Table 4. Rates of Active Ingredients in Quilt

Table 5. Rates of Active Ingredients in Amistar Top

Note: The following information was exctracted based on assessment of the research from Dr. Rick Cartwright. Azoxystrobin (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 to be somewhat more effective on sheath blight than Trifloxystrobin (GEM RC) and vice versa for blast--but the differences were just slight.