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Blue mold risk is fairly low

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By Rick Greenwell

Here are the latest tobacco updates from Kenny Seebold, U.K. tobacco specialist and I thought you would like to read about them.

As of June 22, blue mold has been found in two counties in southeastern Pennsylvania.  Disease has not spread significantly beyond the areas that were reported to have been affected originally.

Over the past week, there has been little chance of spore movement from the Pennsylvania sources into Kentucky and surrounding areas. The overall blue mold risk is fairly low through the beginning of next week.  Thus, I don’t think we need make fungicide applications for controlling blue mold at this time. If the situation changes, we’ll post an alert through the Kentucky Blue Mold Warning System and on the Kentucky Tobacco Disease Information age (www.uky.edu/Ag/KPN/kyblue/kyblue.htm.  As always, since we all know that blue mold manages to show up in the most unexpected places, please continue to watch for blue mold and report any suspected finds as quickly as possible.

On another note, we have begun to see a little black shank and target spot crop up.  With regard to black shank, the best lines of defense are good management practices, planting a variety with good resistance to disease, and applications of Mefenoxam (Ridomil Gold SL or Ultra Flourish). Mefenoxamproducts perform well when applied prior to or just after setting, particularly when a variety with good resistance is employed.  What fungicide options are available to the producer who did not put down Mefenoxamprior to setting?  Syngenta Crop Protection recently released Ridomil Gold SL, which has replaced the EC formulation of this product.  The labeled for the SL formulation of Ridomil Gold differs from that of the EC in that applications of the fungicide are now permitted at 1st cultivation and laybyeven if a pre-plant application was not made.  Thus, Ridomil Gold SL can be used in situations where black shank appears after setting.  These “rescue” applications will be most effective if a variety with moderate-to-high levels of resistance has been planted, such as ‘KT 204’ or ‘KT 206’.  The rate for Ridomil Gold is 1-2 pt/A if the fungicide will be applied at 1st cultivation only; two treatments at 1 pt/A each can also be made at 1st cultivation and layby.  Applications should be directed at the soil and stems of plants for best control of black shank.  The fungicide should be incorporated as quickly after application as possible, either mechanically or by irrigation (natural rainfall or overhead irrigation).  Soils need adequate levels of moisture to activate Mefenoxamand permit its uptake into the plant.  Secondary spread of black shank is considerably less likely in a drought than in rainy weather; however, heavy rains or irrigation could result in heavy losses to black shank in fields with even low levels of disease, so Mefenoxamshould be applied in advance of anticipated moisture events.  The black shank pathogen can be moved easily on equipment and feet!  Growers need to sanitize properly when moving between infested and clean fields.

With regards to target spot, our most effective control for those who face serious losses to this disease is Quadrisfungicide.  Timing of fungicide application is critical to good success with this product against target spot.  We know from previous research that an early (around layby) application of Quadris at 8 fl oz/A allows for good coverage and suppression of disease at a time when disease levels are likely to be low, and this helps prevent buildup later.  This point is important, because low levels of target spot early in the season can lead to large-scale outbreaks after the crop grows to the point that row middles are shaded.  Also, complete coverage (important with Quadris since it is only a local systemic) is more difficult on larger tobacco, so we like to see an early application to get a baseline level of fungicide in place before the crop  grows to a size that is more difficult to spray.  In many cases, a single application of Quadris will give good control of disease; however, if symptoms appear as we near topping, a second application at 8 fl oz/A(10-12 fl oz if pressure is high) will ensure control of disease as the crop matures prior to harvest.  According to the label, we can apply up to 31 fl oz/A of Quadrisper season; however, most growers will need no more than 2 applications at 8 fl oz/A.  In certain high-pressure situations we might need a third application; Quadriscan be applied up to the day of harvest, although we would rarely see a need to put out this product at such a late stage.  As with all fungicides, please consult the label for detailed information on rates, safety precautions and resistance management.