Comments on Disease and Boron from SC Peanut Notes No. 66 2018

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The following comments were provided by Dr. Dan Anco at Clemson University

A lot of good peanuts out there. County Extension Agents Hannah Mikell (Clarendon County), Trish DeHond (Chesterfield, Darlington, Marlboro Counties), and William Hardee (Dillon, Horry and Marion Counties) are seeing no major issues in peanuts so far. Rainfall as usual has varied from field to field, with some fields very dry and others getting plenty of rain.

40-45 Day Reminders

Fungicides: Planting dates and field age are spread out a bit this year. Earlier planted fields have already or are soon reaching the 40-45 day mark and applying fungicides. If fungicide protection hasn’t already started earlier due to increased late leaf spot pressure, 40 – 45 DAP is when we want to make sure our fields are getting protected. If the planned fungicide does not have soil activity against white mold (e.g., chlorothalonil or tetraconazole), addition of tebuconazole (generic Folicur) helps provide economical early season white mold protection. The critical control period for white mold in SC generally starts 60 DAP.

Boron: If soil tests show boron levels below 0.4 lb/A, addition of 0.3 to 0.5 lb elemental boron/A (e.g., 1.5 – 2.5 lb Solubor, additional product rates on page 16 of the production guide) helps prevent boron deficiency. Boron can go out with a fungicide or herbicide application. Watch application rates, more is not always better — applying more than 0.5 lb elemental boron in a season can cause boron toxicity.

More on Miravis

As with most any new product, the approved registration and (limited) availability of Miravis fungicide for peanuts this year has interest and questions. A previous update listed some of its strengths and weaknesses as far as foliar and soil diseases are concerned. Miravis is a Group 7 fungicide with a labeled rate of 3.4 fl oz/A, and it is going to cost more than an average fungicide. There may be thoughts of wanting to try a reduced rate application to reduce the overall price, however at this point I would advise against this to preserve its efficacy as long as possible and to reduce the chance of resistance developing. Along these lines, Miravis would be best reserved for fields and situations where it can be used preventatively (as a general example, not later than 60 DAP) and where yield potential is high and leaf spot pressure or risk is also high. Irrigated Virginia types or highly susceptible runners like TUFRunner 511 are two examples. With dryland production, we can certainly still have good yield potential and/or high leaf spot pressure, but a lot of the yield potential there is also more dependent on the weather, which simply means there is more uncertainty to the return on investment. Runners with more late leaf spot resistance like Georgia 12Y and Georgia 14N would not see the same level of benefit from Miravis as more susceptible varieties and could be managed effectively with other products. Georgia 06G in most cases could also be managed effectively with other chemistries, with the emphasis there primarily being on white mold (e.g., Elatus, Convoy, Provost Opti…).

Dr. Dan Anco

Extension Peanut Specialist and Assistant Professor
Department of Plant and Environmental Sciences
Clemson University – Edisto Research and Education Center
64 Research Road
Blackville, SC 29817
803-284-3343 x261 office
630-207-4926 cell