Georgia Pecans: New Triazole Fungicides Show Promise

Pecan scan on shucks. Photo: University of Georgia

Triazole (Group 3) fungicides were first labeled and used in pecan production during the 1990s with the introduction of propiconazole (Orbit). Since that time, a number of triazole active ingredients and products have been available and widely used.

Tebuconazole in particular has been sprayed heavily in some orchards due to its low cost.  With this use, a shift in pathogen sensitivity has been documented. With cross resistance within the group and the decline in sensitivity, recommendations for use of these products have narrowed.

During the last few years, two new triazoles have been labeled for pecan and do not seem to share the issue of cross-resistance with the previous products. Difenoconazole was first introduced as part of Quadris Top (now labeled on pecan as Amistar Top).  It is also a component of Miravis Top, a new fungicide for pecans which is being used heavily for nut scab this year.

Recently, mefentrifluconazole (labeled as Cevya) has come to the market as a stand alone triazole product.

Yet another product was recently labeled that may be available on a limited basis.  The trade name is Regev, and it is a combination of difenoconazole and tea tree oil. Tea tree oil does provide control of some fungal diseases, although in limited testing it has not been particularly effective on pecan scab when sprayed alone.

The highest rate of Regev will provide the same amount of difenoconazole as found in the high rate of Amistar Top. The table below lists products that contain these active ingredients.

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Difenoconazole and mefentrifluconazole are great triazoles on scab.  In UGA 2019 fungicide trials around Georgia, they were highly effective at all locations.  They offer a number of options as a mixing partner or stand-alone spray.

Price will be a factor in the decision to use, but they are tools that could help growers with high disease and high yield potential.

For Desirable, or cultivars with similar scab susceptibility, the new triazoles can be mixed with azoxystrobin to provide the same combination found in the premixes listed below.

Treatment FRAC Code Active Ingredient (AI) Lbs. AI/Gal Rate Product/A
Cevya 3 & 46 Mefentrifluconazole 3.34 3 – 5
Regev 3 Difenoconazole + Tea Tree Oil 1.67 3.33 4 – 8.5
Quadris Top 3 & 11 Azoxystrobin + Difenoconazole 1.67 1.05 8 – 14 fl. oz.
Amistar Top 3 & 11 Azoxystrobin + Difenoconazole 1.67 1.05 8-14 fl. oz.
Miravis Top 3 & 7 Pydiflumetofen + Difenoconazole 0.63 1.04 13.6 fl. oz.



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