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The North Coast

Greetings,

The last few years I have been working with Carolina Cross watermelons. Reliable success has been difficult to achieve. Subsequent studies have lead me to the hypothesis that the seed stock in general was harboring a pathogen that was holding it back and/or causing it to fail. In collaboration with many other professionals, I have formulated a plan going forward that includes safe disinfection of the seed stock that I am working with. The link below is a study conducted by the U. of Florida and is the basis of my disinfection plan. Peroxyacetic acid(or peracetic acid or PA) is used as a soak to not only sanitize, but disinfect the seed inside and out.

PA is the big brother of peroxide, a super oxidizer. It is rather difficult to get ahold of because it can be a rather nasty chemical, but when diluted as stated it is a remarkable disinfectant. My advice on procurement would be to work through agricultural or academic sources. You can not just call them up and have some shipped.

Watermelon link:

http://apsjournals.apsnet.org/doi/pdfplus/10.1094/PDIS.2003.87.12.1495

PA link, you can read about other uses and applications.

http://www.jetharvest.com/members/lable_pdfs/JetAGrevised.pdf

4/19/2014 4:40:17 PM

The North Coast

As a note, a small amount of active ingredient is needed for the ability to disinfect the seeds. The most ideal time to disinfect the seed is right after it is harvested. So, a person would harvest, soak, then dry. The result, as the data concludes, would be a seed with the genetic potential maximized without anything else holding it back.

I have seed very good results in using this product this season. I am even working with a highly infected lagenaria line with expected results. If you have ever seen the red sap on a lagenaria...well, I am working to understand that too.

In a nutshell, a disinfected seed is a perfect seed. Almost a certified perfect seed in our case. The rest of the cucurbit crops grown in the world for profit have safeguards against seed borne diseases. It may be time for us to think about it too.

As a precaution, this is a very aggressive chemical with burn like actions on the skin. If you are stupid and are not wearing protective eye protection you may suffer lasting damage. At lower concentrations it is more benign.

Grow 'm big!

4/19/2014 4:40:49 PM

Bethlehem CT

Hi Nate I am excited to see the final results using this method.

4/19/2014 9:52:11 PM

The North Coast

By now the results are in as it pertains to this year's attempt to use seed disinfection as a means to control the crown failure of grafted carolina cross plants...and my efforts had absolutely no effect on the outcome. I was really hoping that I was able to get to the bottom of things and to allow the growers to experience the full benefits of grafting. My apologies to all, I feel privileged to have worked with you again.

I believe more than ever that GSB has infected most all of the carolina cross seed line. It's mode of action and mode of spreading makes it quite pervasive. The pathogen is systemic by entering the plant's vascular tissue and moving within the plant. The pathogen doesn't normally kill its host, allowing it to reproduce. Once a plant or a seed line has GSB there may be no way to get rid of it, only suppress it. The watermelon plants genetics have been adapting to the presence of this pathogen during this same long time period also. Our "natural selection" would include the plants that tolerated GSB the most and went on to produce exceptional size. It is a proven fact that this type of baggage in a seed line does hold back performance and output. Any person looking for the best performance out of their seed line, traditional or grafted, would fair better with a disinfected seed.

8/11/2014 4:21:55 PM

The North Coast

As for this year's disinfection using peroxyacetic acid, I trust that the study done by the University of Florida is correct and valid. I was not able to reproduce the disinfection procedure as per the study exactly however. It states that they had a 100% success disinfecting seeds fresh out of the melon. I didn't have that luxury and used the standard dry seed. Possibly it was difference between a soft, fresh seed and a hard, dry seed that did not allow the disinfection to take place? That was my fear going into to it all actually and I did many tests focusing on finding the maximum concentration and maximum soak time without a decrease in germination rates. A person would have to believe that if they used fresh seed and followed the procedure that it would work and mimic the study.

Why do the graft crowns fail? It has to do with the relationship the plant has with its pathogen. The two have been having a relationship for some time and the graft throws out the balance. It is not the rootstock that fails, it is not the graft union that fails, most often it is the area near where the watermelon cotyledon once were. That's the area that starts to exude. Occasionally this exudate can stop but most often it leads to crown failure. This area of the plant is special, it is the location where the roots and the vine meet. It is the vascular junction between the two. There is thin layer of vascular rays that run perpendicular to the vine in this location and it is in this location that problems arise. (On a side note: I have been looking into producing grafts without any portion of the hypocotyl. It would eliminate the failure point but not the root problem. Pun intended.)

8/11/2014 4:22:23 PM

The North Coast

My life is heading north soon to uncharted garden patches and business opportunities. Not sure if continuing the push is in my cards anytime near. I still have enough disinfectant to clean the entire nations carolina cross seed supply but I hope to turn a bit more focus on family and fortune. Cheers and good luck growers.

8/11/2014 4:22:31 PM

Bethlehem CT

Hey Nate Why is it that the Shintosa brings out the problem worse than the others? Last year I did Langenaria and it worked out o.k., and this year I used C. ficifolia and it seems o.k. In fact it actually has helped a ton as they are the only two plants with out wilt.

8/11/2014 7:42:38 PM

The North Coast

I have seen all of the rootstocks fail, some more than others. Shintosa imparts the most influence on the watermelon as rootstocks go. Subsequently, it has the highest failure rate. The common factor in nearly every graft is visible expressions of gummy stem blight.

Over the years I have had correspondence with a few really intelligent professionals about this issue and while they could tell me what is going on they could not tell me why. I was dealing with an agricultural issue that was not fully studied, experienced, or known in this country. That has lead me to my own testing and my own theories, and they are just that theories. The idea that Carolina Cross is infected with GSB is the most plausible explanation of outcomes we are seeing. With that said, I could be proven wrong as time goes on. If I were to be proven wrong I would be elated, because we would then be closer to solving the issue.

The author of the study below has been my best source of knowledge and has helped me a great deal. He was intrigued by the issue of grafted watermelon crown failures and he conducted a study using fungicides during the procedure. During the off season I hope I can get a little closer to finding a good solution that allows for success. I do have confidence that full nature of the infection will be discovered and then hopefully, a solution presented.

A summarization of the study:

http://www.nationalwatermelonassociation.com/pdfs/Controlling%20Gummy%20Stem%20Blight%20on%20Grafted%20Watermelon%20Seedlings%20with%20Fungicides.pdf

The long presentation of the study:

http://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS-12-12-1133-RE

Cheers.

8/20/2014 9:54:10 AM