I have taken my Tractor Driven Rotor Tiller and dug up all the dead Blight Stricken Kerria Japonica. I have raked it out of the ground and destroyed all the residue of the Blight Stricken Kerria Japonica!! What I would like to know is how to treat the ground where the blight Stricken Kerria Japonica was?
While Kerria japonica, a member of the Rosacea family, does not have serious disease problems it is susceptible to blights. The blight infecting your Kerria is likely Fire Blight, a bacterial disease which infects many members of the Rosacea family. The bacteria causing Fire Blight overwinters almost exclusively in cankers on limbs infected in the previous season. Once the shrub or tree resumes growth in the spring, the cankers become active and bacteria multiply and ooze from branch surfaces. Splashing rain or insects transmit the bacteria to other nearby plants. The bacteria enters the plant through injuries on tender young leaves and shoots, caused by wind, hail, or insects.
You have already taken the most effective step toward controlling future Fire Blight infections by removing and destroying the infected plants including the root system. As there are no cures for bacterial infections on plants, preventive measures are very important. The following practices are recommended:
Choose resistant cultivars for this site going forward.
Remove infected material as soon as any symptoms are discovered. Prune the affected limbs 30 cm below any visible lesion. Discard all material removed by putting the material in garbage destined for a landfill or burning the material if legally allowed to do so.
Use sterilized tools. Sterilize your tools before using them to remove infected material. Any wound can inadvertently spread a bacterial disease. Sterilize your tools after removing infected material before you use them on another plant.
Use watering techniques that apply water to the root zone of the plant not to the foliage. The bacteria needs a film of moisture on the surface of the plant in order to infect the plant.
Give plants time to toughen up for winter. In late summer, stop fertilizing, heavy pruning and even watering which will promote new growth. Soft new growth is most susceptible to bacterial disease and to cracking during freezing weather which provides more entry points for the bacteria.
Finally, note that Fire blight infection is highly influenced by weather. Warm weather with intermittent rain or hail provide ideal conditions for the development of the disease.
What’s Wrong With My Plant, D. Deardorrff and K. Wadsworth,Timber Press, 2009
Pests in Gardens & Landscapes
University of California Agriculture & Natural Resource