Many growers are experiencing a late season and that means young, tender crops can be more vulnerable to fungal attacks. As temperatures warm quickly and activate fungi faster than crops can grow, this imbalance can have a big impact on crop yield potential and warrants vigilant scouting and timely treatment.
Application Timing for Soybeans
Key timing for application of fungicide in soybeans is R3, when most pods have set, but before extension or pod fill. Effective fungicides only provide 21 to 28 days protection from foliar disease, so it is sometimes best to aggressively scout fields and delay fungicide application until R4.5 as long as foliage stays clean. More common is an R3 application, followed by a scout-and-spray approach, with a follow-up application as needed.
DuPont offers growers two tools to stop fungal diseases and protect yield potential. DuPont™ Aproach® is a single active strobilurin, while DuPont™ Aproach® Prima is a premix of the strobilurin in Aproach® plus a premier triazole, cyproconazole. Both fungicides deliver preventive and curative control with residual and systemic activity throughout the plant.
Aproach® and Aproach® Prima control many soybean diseases, including frogeye leaf spot (even strobilurin-resistant), aerial web blight, cercospora blight, rusts, mildews, and pod and stem blights. Soybean research trials at the University of Tennessee show significantly reduced disease compared to other fungicides.
Insect damage is another concern at the R3 growth stage. If scouting reveals insect pressure, consider tank mixing1 with an insect product, such as DuPont™ Prevathon® insect control. Prevathon® provides 21-day residual to protect crops from worm pests such as corn earworm, fall armyworm, beet armyworm, velvetbean caterpillar and soybean looper 2.
Application Timing for Corn
For optimum beneficial crop response, apply Aproach® at V4 -V6 (this can be tank mixed with postemergence herbicides) followed by Aproach® Prima (6.8 fluid ounces per acre) at VT-R2. For less intensively managed corn, a single Aproach® Prima application protects foliage during the reproductive stage of the corn crop.
Avoiding Fungicide Resistance
Overuse of any fungicide increases risk of rapidly developing resistance. Many fungi are polycyclic, meaning they will reproduce spores in multiple cycles during the growing season. Each reproductive cycle presents another opportunity for resistant spores to appear and replicate. Some fungi pose a greater risk than others for resistance development, including rusts, powdery mildews, leaf spots and blights.
Tucker Miller, an independent crop consultant from northern Mississippi, recommends Aproach® Prima to his growers for control of resistant frogeye leaf spot and other diseases. “Having an extra mode of action with Aproach® Prima is a great benefit,” said Miller. “Because of the resistance factor, instead of one mode of action, we have two. That has been a proven tactic in resistance management. We can have a control component as well as a preventive component.”
DuPont Crop Protection is collaborating with the Fungicide Resistance Action Committee (FRAC) to monitor plant diseases and identify best practices to reduce development of fungicide resistance. A University of Kentucky plant pathology fact sheet, Principles of Fungicide Resistance, provides more on how diseases develop resistance to fungicides.
1Always read and follow all label directions and precautions for use when using any pesticide alone or in tank mix combinations.
2This Prevathon® recommendation is permitted under FIFRA Section 2(ee) for the control of cabbage and soybean looper, southern armyworm, green cloverworm, velvetbean caterpillar in soybeans in the states of Alabama, Arkansas, Georgia, Kentucky, Louisiana, Mississippi, Missouri and Tennessee and has not been submitted to or approved by the EPA. The 2(ee) expires on 12/31/15.
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