T U R F TA L K
Fungicides: What a “Generic” Topic By David S. McCall, Turfgrass Research Specialist, Virginia Tech ithin the past few years, an increasing number of “generic” fungicides have become available. As patents run out on the active ingredients in brandname fungicides, other manufacturers can make and sell those ingredients under different product names. When this is done, some problems can arise, such as improper formulations or different percentages of active ingredient, both of which can alter the required use rate. In some instances, a modified formulation may cause more phytotoxicity or reduced efficacy.
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Research methods Previous research at Virginia Tech tested various brand-name products from BASF, LESCO and Makhteshim-Agan of North America (MANA). In this year’s studies, we compared a generic formulation of chlorothalonil (from MANA) to Daconil Ultrex, generic propiconazole (MANA) to Banner Max, and generic iprodione (BASF) to 26GT, respectively, for control of Rhizoctonia blight (also called brown patch). We tested each of these products on a creeping bentgrass green in Blacksburg. Propiconazole products were also compared on turf-type tall fescue on a sod farm in Doswell, VA.
Research results Weather conditions in 2005 were ideal for brown patch. In our bentgrass trial, we began to see moderate disease pressure by June 27, and the disease progressively worsened through July 12. During moderate disease pressure, both application rates of chlorothalonil (1.875 & 3.75 oz./1000 ft2) provided excellent control for each product. However, as disease pressure increased, the efficacy of each rate of MANA-chlorothalonil was slightly lower than Daconil Ultrex. Similarly, while disease pressure was low, Iprodione Pro performed slightly poorer than 26GT. As disease pressure increased, neither product adequately controlled the disease.
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TENNESSEE TURFGRASS
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At the highest rate of propiconazole tested (3.2 fl. oz./1000 ft2), each product successfully controlled Rhizoctonia blight. MANA-propiconazole and Banner Maxx performed similarly at this rate, as well as at 1.8 fl. oz./1000 ft2. Again, at the lowest rate (1 fl. oz./1000 ft2) the MANA-propiconazole did not perform as well as Banner Maxx.
Recommendations • When disease pressure is relatively low, a generic fungicide formulation may provide adequate control; however, as disease pressure increases, brand-name fungicides often perform more effectively. • When using generic products, always study the labels first, to make sure that you’re applying the proper amount of active ingredient. Don’t make the assumption that your old “standard” rates will apply. For example, LESCO Spectator T&O Fungicide contains propiconazole, as does Banner Maxx. However, the amount of active ingredient in Spectator is 41.8%, roughly three times that of Banner Maxx. Therefore, to achieve similar results, Spectator’s product use rate is lower than that of Banner Maxx. If applied at equal product rates, you may get greater control with Spectator, but you’ll also see significantly more phytotoxicity (not to mention fail to follow the label). • Check to see how the generic formulation compares with brandname products in university testing. Though the active ingredient may be the same in both products, inert ingredients (such as surfactants) may not be the same. This sometimes leads to decreased/increased performance or increased/decreased risk of phytotoxicity. • Take into account that the original manufacturer has years of experience with the product. The sales and technical staff will have a thorough understanding of the product’s limitations and compatibility issues. Many generic manufacturers are just now spending more resources to gain a better understanding of their products.
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