2015 Wet Spring Leading to Potential Brown Rot Issues

Brown Rot in Gulfking
Brown Rot in Gulfking

I hope that everyone is having a good harvest so far, although I will have to say it’s been challenging with all of the rain we have had here in Central Florida.

One issue that we don’t often have to deal with is Brown Rot.  However, with the afternoon rainshowers that we have had (in some cases over 3 inches over the past couple of weeks), it is showing up in some of the harvested fruit, particularly in the bottom part of the fruit.

We are working on an EDIS publication for future reference; however here are some quick points.

Brown Rot

Brown rot is caused by a fungus, Monilinia fruticola and is often an issue in areas with frequent rainfall during fruit development.

Primary infections occur in the spring and can lead to flower death and reduced yield, but secondary infections affect the fruit.  In addition, abortion of mature fruit, e.g., “mummies” that fall to the orchard floor can serve as inoculum for future infections with later ripening periods.

G. England
Brown Rot in Mature Fruit, G. England

Disease Cycle

The continuous production of spores by mummies, cankers, and apothecia fuel the disease cycle and the infection of blossoms and fruit. Brown rot flourishes under conditions of high humidity (>94%) and optimal temperatures occur around 77°F (25°C). Rain, wind and insect activity lead to the release of spores that initiate the infection.

Secondary infection occurs as blossoms and shoots that have been initially infected begin producing spores, and can continue to do so until early June. If secondary spore production can be prevented by the use of effective management techniques, the disease can be more easily contained. The presence of infected fruit and mummies can also act as a source to spread brown rot.

Management

Management for brown rot should begin before anticipated rain events occur, and guidelines for recommended fungicides are listed in the SE Peach Spray Guide: http://www.ent.uga.edu/peach/PeachGuide.pdf.

Please remember to rotate your fungicide chemical classes (as indicated by the FRAC codes) to avoid resistance risk.  There have been races of brown rot that have been identified as resistant to certain classes of fungicides – although there is a fungicide resistance kit that can be ordered to verify that the fungicide is at fault.

Key Points

As always – if you have any questions or concerned, please let me know!

Cheers,
Mercy

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Phomopsis Constriction Canker

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.

phomopsis on branch
Phomopsis Canker on Branch (Clemson University)

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.

Additional Comments:

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!

Happy Harvest!

Images

 

 

Phomopsis Constriction Canker