There is some good research that shows that composting diseased plant tissue can be beneficial because the organicism that digest this will develop immunities to those diseases. Go ahead and compost that stuff.

Composting diseased plants is highly debated - another current discussion on it further down the page and many prior discussions about it here as well if you want to review them - so you won't get agreement on it and ultimately it will be your choice. Some will say never do it. Some will swear it will be the death of your garden, some say only for use around ornamental plants.

Like Kimmsr, I trust the process to handle diseased plants and have for many years so I compost diseased plants without a second thought. And since most garden disease problems are air borne as well as soil borne, NOT composting your diseased plants doesn't keep you from getting the disease in the future.

Dave

Thanks. Yeah, I saw the discussion about diseased plants in general, but somehow I thought I could get more specific info/reassurances when the particular affliction is identified.

Nevertheless, good points brought back up that my skimming of that thread didn't catch. They'll be thrown in. Thanks.

I have continual problems with diseases in my garden. I have strange wilts that hit the rhubarb, cukes, basil and other stuff. I move things around and rotate crops and it doesn't help. I feed the soil, feed the plants, it just gets worse. I begin to wonder if I'm just recycling diseases by composting, but I can't prove it one way or the other.

Sir Albert Howard noted that one group of peoples in India where he was stationed as the Ag Agent could grow both healthy plants and animals right next to farms of other peoples that had both plant and animal diseases. The difference between farming practices was that the people with the healthy plants and animals composted all the animal and vegetable waste and then spread it on the fields. After studying how these people did all of this he then wrote a book about it and proposed that if these practices were followed good results would follow.
There are many people that have substituted one kind of fertilziers with another kind of fertilizers that think they are organic, but are not really, that doubt that what Sir Albert Howard wrote will work because they are not following his advice. Lady Eve Balfour and Friend Sykes took farms that had problems with disease and were loosing large quantities of money and, using the practices espoused by Sir Albert, made those farms healthy and productive.

I wouldn't worry about powdery milder in the compost. PM is everywhere, all the time. When your plants are susceptible to it, the *will* get it, regardless of your immaculate compost pile.

Hiya, a bit late to the game but @kimmsr if you have the sources for the research you're referring to I would love to check it out. Thanks

There are two categories of plant diseases that
affect plants. “Abiotic” diseases have no pathogen, and are
generally caused by any of a number of cultural factors. Since there is no pathogen, abiotic diseases are
not infectious. Cultural factors like light, temperature, soil
chemistry/soil structure, media air:water ratios, air pollution, pesticide/herbicide residue,
insect herbivory, ….. can individually or collectively cause
abiotic diseases, or, even though not infectious, set the stage for
“biotic diseases”, which involve living pathogens. In this case,
the OP asks about the infectious/fungal/microbial pathogen, powdery
mildew. Fungi are the most common pathogen affecting plants in our
gardens, but bacterial and viral pathogens are sometimes players, too (even though there's a
question re whether of not viral particles are living OR microbes –
not really applicable to this topic).

Plant pathologists often describe the disease
process using a 4-sided figure called the disease tetrahedron (think
“pyramid – 3 sides + the bottom).

Each side of the tetrahedron
represents an essential part of the infection process. There must be
a virulent pathogen (capable of infecting the plant) which is
genetically capable of recognizing its host. Either the environment
must be conducive to the development of the pathogen, or the pathogen
must be able to stress/weaken the plant. The 4th requirement is the
time required for diseases to develop and spread. Whenever conditions
are such that any one (or more) of the 4 requirements is missing from
the equation, there is no immediate threat.

Since the best medicines are prophylactic, the
grower who makes sure plants are healthy and not stressed is ahead of
the game. Biotic diseases are better able to overcome the natural
defenses of plants weakened by stress that occurs when the plant is
forced to deal with cultural conditions near or beyond the limits the
plant is genetically programmed to deal with. These would be plants not growing in the light, temperature, soil, fertility, ....., "sweet spot".

Circling back to the disease tetrahedron, we can see compost that
contains the virulent inoculum provides 2 of the 4 essential sides
needed for a disease to develop – environment and inoculum. Time,
the third essential side will not likely be on the side of the
grower, so you can't use that to your advantage. We know there will
be potential hosts (it'sa garden!), but not whether the hosts will be
susceptible to the pathogen, or weak enough for the pathogen to
infect the host. When you start to analyze, it doesn't make a lot of sense to take the position you'll build the size of your compost heap at any cost.

Al

^^^^^

Kimmsr

There is some good research that shows that composting diseased plant tissue can be beneficial because the organicism that digest this will develop immunities to those diseases.

What adverse effect does diseased ( such as powdery mildew afflicted) plant tissue have on the organisms digesting said tissue in the compost pile?

Probably diseased plant tissue has no impact on the organisms that digest such tissue, except to be food for them. Even if it did have a negative impact on some of them, there are tens of thousands of different bacteria and fungi in a pile, plus insects and worms and everything else. It would be an EXTREMELY rare situation for some diseased tissue to harm even half of them. They all eat and decompose various things and each other, and some would reproduce quicker than others for a while, and then run out of those special conditions, and then others would catch up.

(Note: I wrote tens of thousands just say "a whole lot, probably more than we could even contemplate" - entirely possible or even likely that the number is many times that, there are astounding numbers and types of microorganisms in compost and soil.)

And for a dissenting view.........I have NO issues with composting plant parts with powdery mildew! The spores are unlikely to survive even a slow ("cold") composting operation and PM is an obligate fungi, meaning it requires living plant tissue to survive. And there are literally thousands of different types of powder mildew and most are very host-specific. So even if the spores did perchance survive a composting process, they will not wreak widespread havoc on a garden but only affect their original hosts.

In the vast majority of cases, PM is far more of an aesthetic or cosmetic issue than a source of actual harm to the plant and easily controlled by cultural conditions.