Rose Rosette Disease - A Follow-up
As mentioned in my previous article, the most effective miticide against this critter is dimethoate (Cygon®). However, because of its high toxicity, it may not be available to the average rosarian. Other, less effective, pesticides tested were diazinon and carbaryl (Sevin®).
In lieu of pesticides, Dr. Philley recommends that we rosarians first monitor our roses for the disease. If we detect the tell-tale "witches broom" with chlorotic leaf tissues and bright purple veins on new foliage, then we should remove the offending stem and most of the cane to which it is attached. Continued monitoring for the disease is paramount. If additional canes are noted with the disease, then the shrub should be removed. Be particularly aware of the roses near the diseased rose.
Asked if sterilizing the pruning equipment between cuts or between shrubs is recommended, Dr. Philley indicated this was not necessary. There is no evidence to suggest pruning or grafting equipment can transmit the disease - only the mite. There are several diseases which, if exposed to the air, become non-transmittable. This disease appears to be one of them.
That said, my personal preference is to err on the side of caution. Whenever I deal with diseased plants (of any type), I always sterilize pruning equipment between shrubs. [Old habit, I guess. And teaching an old dog like myself to learn new tricks takes a bit of training. :>D] I prefer to use a hydrochloride (bleach) solution @ 1/2 cup bleach per 1/2 gal. of water. This will discolor the pruning blades and metal parts, but this discoloration can be cleaned with a steel wool/soap pad like Brillo or SOS. The blades should then be resharpened and oiled.
Although I specifically asked if alternative pest controls had been used for controlling the mite, none have been so tested. However, Dr. Philley noted that in field observations where natural predators like predatory mites and thrips were evident, the pest mite did not exist - even in highly infested wild stands. This encourages me to believe that predatory mites like Phytoseiulus persimilis can be applied to the rose garden for a natural biological control. It also suggests that the use of pesticides benign to beneficial predatory insects and mites can also be used. Such products as whole neem oil (Rose Defense™) would be recommended here.
One thing is for certain. Rose Rosette Disease is 100% fatal to the rose. In southern
Latest Articles