endangered avocados and grafting

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endangered avocados and grafting

Post  Nina on Wed Aug 12, 2009 1:31 am

There's a terrible new disease attacking Red Bay trees along the southeast coast of the US. That's bad enough, but what makes this a major catastrophe is that red bay is a wild relative of the avocado, and the disease just hit Homestead, FL, home of the east coast avocado industry. Avocado wilt is vectored by a bark beetle- a very FAST bark beetle- and is spreading much quicker than anyone expected. Our unit agreed to house avocado rootstock until the USDA in Florida could graft scions from important cultivars in their collection onto it. This week a scientist is sitting in our greenhouse feverishly grafting, all day long. When he finishes, the plants will be sent to Hawaii, where they will (with luck) bask in the sun and prosper, be tested for resistance for this pathogen, and eventually be used in a breeding program to try to restore the crop to Florida if the worst happens. It's not clear at the moment how bad the disease will be on avocados. It's probably going to wipe out red bay.

Anyway, he needed some equipment, so I lent him some of mine, and in return, he taught me how to graft. He's spent his entire career doing it, so I thought I'd pass on what he said. I can't vouch for any of it, but he sure looked like he knew what he was doing. Some of this is not applicable to bonsai, but some of it is.

First, you top your rootstock two weeks before you want to graft, and you cut every leaf in half. The idea is to get the plant in the mood to regenerate. Then you need the right equipment. This guy doesn't use grafting knifes- he says he uses an exacto knife with a heavy duty blade that isn't very flexible but is very sharp. He said a sharp knife makes a huge difference. He also used "bud graft tape", not regular grafting tape, and not that green stuff. As for the scion: you want one that's pointing up on the tree. If it's pointing down, it won't take. He said that was because of the plant hormone balance in the twig [I have no idea if this is true- it sounds "truish". Auxin is produced at apical buds and moves down the stem normally]. He then showed me how to quickly cut the scion in a "V", then quickly cut a slit in the rootstock trunk- the trunk shouldn't be much thicker than the scion for optimum results. Insert the scion, tightly bind with tape, and then use parafilm to make a big cocoon around the scion. If you don't have parafilm (and it's extremely expensive), you can just put a plastic bag over the whole top of the tree. However, you need to watch the tree and remove any buds breaking on the rootstock, so parafilm is better since you don't need to bag and unbag the tree all the time. According to him, the new leaves on the scion will pop through the parafilm all by themselves.

It's unbelievably hot in Maryland this week (hitting a hundred yesterday), so it's funny to see this Florida guy sitting in the stifling greenhouse remarking on how nice and cool it is here in the North.

Nina
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Re: endangered avocados and grafting

Post  Kev Bailey on Sun Aug 30, 2009 1:53 pm

That's an awful scenario for the Avocado growers.

Thanks for the grafting info though. All well informed practices are useful for adding to experience. I bought 50 Japanese Maple whips to have a go with sometime. I've got large plants of Coral Bark, Deshojo, Shishigashira, Makiwa Yatsubusa, Kamagata, Kiyohime and Seiryu for scions.

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“It is not the strongest of the species that survives, nor the most intelligent. It is the one that is the most adaptable to change.” - Charles Darwin.

Kev Bailey
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Re: endangered avocados and grafting

Post  Nina on Sun Aug 30, 2009 8:48 pm

I think I'd use this technique to add a branch to an existing tree, but I'm not sure if it's the right technique to graft a cultivar onto another rootstock- the person who's an expert on that is Brent. In this case, the guy was using this technique because he was sure of a 90% take, which he needed if he was going to suggessfully save the germplasm. He wasn't interested in appearance. Still, I liked the idea of the parafilm "tent".

Nina
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