I am thinking that some of my citrus, especially my pummelos/pummelo hybrids, are struggling with Phytophthora in the soil. I am not the only one having this issue in my neighborhood. Both neighbors are also seeing the identical same issue. The trees just look terrible, all over decline. I've posted photos before, and some have commented that they look horribly nitrogen deficient, which is not the case. Nor is this a pH issue, I am convinced, as my pH simply isn't that high. Nothing to cause this sort of really catastrophic decline. I am much more inclined to believe this is Phytophthora in my soil. We do have this in the S. California, San Diego area, especially those of us close to the coast. I have about every fungus I could have in my yard, due to my heavy vegetation and perfect temperatures through the winter (very mild, frequently in the perfect fungal range of 55-65 in the winter.) So, short of trying to find a soil lab to confirm, I am thinking I'm just going to treat. I am wondering what is the most effective soil treatment for this, how to apply, name of product, etc.

My trees have also been struggling Phytophthora lately. I've treated them with Bayer's fungicide three times so far, with a week or so, gap between each application. Product name is Aliette, it is a fungicide with fosetyl aluminum as an active ingredient. Concentration which I've been using on my citrus is 2.5 grams per liter which is the threshold concentration, I think.

Igor

Igor, are you doing this as a soil drench, then? For us in the USA, Aliette is a commercial product and quite pricey. I'll see if I can find a source.

Patty, I think it's okay to be applied to the root zone, too. Although, I rather prefer it as a foliar application, which is perhaps the faster way for you to achieve the results. It doesn't have to be Aliette, as long as it's a systematic fosetyl aluminum based fungicide, you're good to go. Just be careful to read the specification sheet, as the concentrations differ from each other.

Igor

This is what I use;

http://www.bioworksinc.com/products/shared/rootshield-plus.pdf

Thank you, turtleman! I was a bit worried about wiping out my beneficial organisms. I've been working hard to add organic matter to my very thin DG soils, and of course the whole idea is to encourage a healthy microorganism growth. I will check into this, really appreciate it. Commercial fungicides are some very nasty stuff. And, we have to be careful here with the amount of copper we dump into our soils, as we're so close to the ocean, and everything runs down into it here.

The product literature primarily frames this in terms of a preventative and growth aid. Does anyone have any experience in using it as a treatment for an established phytophthora infection?

I'm not sure if we're speaking of the same product, but Bayer Aliette fungicide has a preventive as well as curative effect on already-affected trees. At least it is mentioned in the specification sheet that came along with the purchased product.

Sorry, I should have specified that I was referring to the product Turtleman posted a link to: Rootshield Plus.

I use the granular product as a greenhouse propagation soil amendment for propagation,, so that product wont do well as a drench....

BUT!

that same product is available as a wettable solution.. Added to irrigation micro's add to your root system

The chemical used commercially for phytophora is paclobutazol.

I did have details of treatment levels but don't know where to find them now.

Maybe there are some details on web.

The bayer produce mentioned was from memory the retail formulation of the chemical. Not sure it is licenced for home use anymore.

The chemical used commercially for phytophora is paclobutazol.

I did have details of treatment levels but don't know where to find them now.

Maybe there are some details on web.

The bayer produce mentioned was from memory the retail formulation of the chemical. Not sure it is licenced for home use anymore.

Phytophthora is the most serious soilborn disease of citrus, and is endemic to all citrus growing areas of the world. The most serious disease caused by phytophthora is gumosis, also known as foot rot, followed by phytophthora caused rot rot. Lemons, limes, sweet oranges, grapefruit and pommels are very susceptible. Before chemical treatment is used to control phytophtora, proper cultivation practices must be initiated. Adequate soil drainage is absolutely essential, because poor drainage and over watering combine to promote buildup of pathogen populations in the soil. Also the soil surface under the tree must be kept free of weeds and debris. The disease can be controlled to a great extent by using the proper rootstocks. Rootstocks vary in susceptibility to the different diseases caused by phytophthora but most all commercial rootstocks, EXCEPT sweet orange and Cleopatra mandarin, are resistant or tolerant to the development of infections of gummosis (foot rot). In ascending order of tolerance to root rot caused phytophthora are cleopatra mandarin, sour orange, rough lemon, rangpur lime,and carrizo and troyer citranges. Trifoliate orange and its hybrids are considered highly resistant to plhytophthora bark infection, AND also tolerant to root rots. To important systemic fungicides metalaxyl and fosetyl-Al are effective against phytophthora and provide control of diseases caused by the fungi in the field. However, when used as a substitute for proper sanitation, metalaxyl leads to the development of resistance. Applications of fosetyl-Al and metalaxyl are alternated to minimize the development of resistance to the fungicides. - The VERY best to you and your wonderful collection of citrus trees, for the successful control of this dreded disesee. - Millet

Thanks, Millet. I am using Agri-Fos (phosphorus acid), which is the treatment of choice here, by commercial citrus and avocado growers, and it is slowly working for me. My very badly affected trees are turning around slowly. We have several different strains of Phytophthora here in our soils - both the species that affects citrus as well as the one that affects avocados. So it will just be something I have to apply regularly until me trees become very well established. And, I probably need to completely re-vamp my watering system, and knuckle under and set up opposing 180 degree micro sprinklers at each tree, and more carefully monitor my watering. Just hard to to while working full time. Hopefully this spring I can tackle the watering system.

Hoosier,
I've found phosphorous acid (and, as Millet stresses, good cultivation and irrigation practices) very effective.
My girlfriend's father has one citrus (Owari on Kuharski-carrizo)that had never put on size or produced fruit, despite being in the ground for several years. Last fall, I took a look at it and noticed gummosis on the trunk, and asked how frequently he watered it. "Daily" was the reply. We treated with a soil drench of Mono- And Di-potassium Salts Of Phosphorous Acid, and sprayed the entire plant (the drench was high-strength, the trunk spray was diluted a bit more and the leaf spray diluted still more, according to the directions). Two days later, I transplanted the tree across the yard (the root ball was about the size of a gallon pot), gave it another soil drench and spraying, and then waited until after the next good rain to give it some mycorrhizae. Since then, it has only been watered to get it re-established after the transplanting, and perhaps once or twice this summer during a few-weeks' drought. The gummosis lesions on the trunk have healed over, and this summer the tree hasn't stopped flushing - five flushes, I think, which have literally tripled, if not quadrupled, the size of the tree - and produced the first fruit since it was planted six years ago.
Best of luck in controlling your phytophthora.