Hello Everyone! I hope that your harvest is going well and that everyone has been getting good prices for their fruit.
Dr. Phil Brannen, pathologist at the University of Georgia sent this along earlier this week, and I thought it would be good to keep an eye out for this in our orchards this year, especially since we have had so much rain and wet weather.
From Dr. Brannen:
I had a call this morning on Phomopsis constriction canker. This is one of the diseases for which we don’t have great answers – certainly not fungicide ones anyway. Some peach varieties are susceptible, and the wet conditions last fall and this winter/spring have likely contributed to the degree of disease observed; the initial infections are thought to occur on buds and leaf scars. The question was asked as to whether pruning out infected tissue would be of value, and the short answer is that I don’t know for sure, but I think it might be for two reasons: carryover inoculum for infections next fall and possible fruit rot.
As far as I know, I have never personally observed Phomopsis fruit rot, but in going over information in my files, I found the following note from George Philley, retired extension pathologist from Texas A&M. He stated, “I saw more Phomopsis fruit rot. It is usually just a novelty type disease, occurring rarely from time to time. Mid to late season I found it in my peaches more often than you would like. It was hot and dry. No brown rot problems at all. I think a good common name for this disease is ” crater rot”. The flesh melts away forming a nice little crater in the fruit. I am unofficially calling it crater rot because I use that terminology in describing the disease to someone. I don’t like using fungal names, like Phomopsis, for common disease names.” I guess “a rose by any other name” comment would be appropriate, but I don’t like the idea of Phomopsis spores raining down on developing fruit. In our 2014 Southeastern Peach, Nectarine and Plum Pest Management and Culture Guide, we state that “Phomopsis or Botryospheria pocket rots are best managed with a tank mix of Topsin-M plus captan, beginning six weeks before harvest.” In reality, I have no idea from where that recommendation was derived, though I have no reason to refute it either. Based on Phomopsis disease recommendations in blueberries, captan does have moderate activity on Phomopsis, so incorporation of captan in cover sprays may be a good recommendation; the addition of a little Topsin would not hurt, assuming that resistance has not occurred to this class. The DMI materials Indar and Quash are also among the best fungicides listed for blueberry Phomopsis twig blight management, as is Pristine; as a result, I am hopeful that Merivon and possibly Orbit (propiconazole) products might have activity as well. Abound has been reported to have activity in peach, as well as captan and DMIs. Therefore, other than adding captan (and possibly Topsin M) to the cover sprays, I think our regular brown rot program will likely be as good as it gets for Phomopsis fruit rot management.
Pruning out diseased tissue does often have value for reducing disease in future years.
It is not perfect, but it does help, and I think it is likely to be beneficial enough that it would pay for itself. Based on one of the attached papers, you don’t need to remove the cuttings from the field to get the benefit of pruning out the infected tissue. I still would prefer that the prunings be flail-mowed as a matter of practice, but there is no evidence that this would benefit Phomopsis canker disease management. Multiple fall applications of fungicides would be required for suppression of the canker stage of the disease, and control through fungicidal means is definitely cost prohibitive.
Keep any eye out for sunken lesions that appear silver in the fall – these can lead to spore release if we have a wet spring. Also – be sure that those with significant fruit on their trees still – keep an eye out for Brown Rot and stay up on your fungicide applications as best you can with the harvest.
If you have any questions, please contact me or your favorite extension agent and we can help!