Some of the reports involved multiple fields with strong inoculum production. During the past week, low levels of new activity were confirmed in southeastern Kentucky - in Pulaski, Breathitt, and Jackson counties. In addition, the first confirmed case from western Kentucky was reported - a single field in Logan County with scattered, older lesion on the older leaves.
Growers are finding low levels of blue mold in shady areas of fields, mainly on ground suckers in crops nearing the topping stage. In Breathitt County, the field scouted had new blue mold lesions developing on July 10 at about 1 lesion/2000 plants on a crop planted mid- June and growing quickly.
Conditions have not been favorable for rapid and widespread development of blue mold in Kentucky. Plant growth and development has improved, so much more of the crop is now highly susceptible to blue mold. Growers need to be especially watchful of the disease building up in fields of older tobacco (especially on ground suckers), without causing much damage, with those spores serving as an inoculum source to infect rapidly growing younger crops in the community.
Bright sunlight much of the past two weeks should have been lethal to most spores moving during the daylight hours, so new activity should be confined to shady areas, especially with shade from the west from trees or ridges.
Once a crop canopy closes, however, movement of live spores within the field under the cover of the canopy is possible. Night conditions have been favorable for both sporulation and infection in most of the eastern third of Kentucky during the past two weeks. Where fog remained until mid- morning, spore movement would have had more
protection.
At this point, we have found no evidence that Kentuckys tobacco growers introduced blue mold on transplants. This is the first time we have been able to say that in many years. Consequently, blue mold is a much more manageable disease within the local community, because the pathogen must still arrive in each community and then build up to damaging levels, rather than already be producing inoculum at damaging levels; which would have been the case with this years weather had we introduced it with transplants.
This warning system and good scouting programs should be especially helpful to growers in their management of blue mold under these conditions. Fields in watch/warning areas should be scouted at least twice weekly for new blue mold, with aggressive spray programs initiated with Acrobat MZ should the disease be found in the field. Why this fungicide and not the inducer, Actigard? Because we want to stop inoculum production on that farm, which Actigard will not do!
Widespread fungicide application within counties should not be warranted unless strong centers of blue mold are present within the community or a large mass of inoculum outside the state becomes threatening. Once plants reach 18 inches in height, Actigard 50W can be used to greatly improve the plants tolerance to blue mold where growers desire that additional protection.
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