Phytopthora Root Rot

I’ve been promising a tip sheet on Phytopthora, and here it is!!! (as an aside: it’s also spelled Phytophthora, but we’ll stick with Phytopthora). This is going to be simple and straight forward advice, because I think any of the scientific detail or “university jargon” used in scientific papers is about as boring as watching paint dry!

I believe that this is the disease that has ravaged many plants in the area, especially Bottlebrush (Callistemon) and Japanese Blueberry (Elaeocarpus). Basically, Phytopthora is a root rot disease (working similar to Cotton Root Rot) that can be brought on by a wicked combination of a wetter-than-normal fall weather coupled with a wetter-than-normal January/February, which also immediately follows freezes in early January. It was already notorious for ravaging Japanese Boxwoods.

After talking with some plant disease diagnostic experts at Texas A&M and hearing what folks like Bob Patterson at Southwest Fertilizer are seeing and recommending – the advice is to spray the plant and drench the soil with the Garden Phos Systemic Fungicide from Monterey. (Garden Phos is also known as Agri Fos).

The most important part of this is the soil drench. And while I agree with that recommendation, I also understand that you’re not going to find Garden Phos everywhere. Thus, if you can’t find the first recommendation, then look for Captan for the soil drench and any liquid systemic fungicide for the foliar spray.  It’s critical to do this application more than once, and it can and should be on a monthly basis, until you’re convinced the new growth coming out is no longer ravaged by the Phytopthora disease.

Some solid advice during such applications as reminded to me by Bob Patterson at SW Fertilizer is to make sure you pull the mulch away from the plants at the base. He further suggests, if possible, to use something like a spading fork to carefully poke holes into the soil, anywhere from 4-6 inches deep, so that the liquid drenching penetrates further into the root zone or getting quite literally to the root of the problem, where the Phytopthora actually exists.

Lastly, if any of these plants died from this root rot, I would still recommend treating the area after pulling the dead plant, especially if you’re going to do any kind of replanting.