Not necessary. PM spores need plant tissue to survive. If you carefully remove all the affected plant parts and clean up well, you will be fine. PM is primarily climate related, not a soil issue.

Thank you! I did chop some up with the mower to fit them in bags. I‘ll spray the blades for safe measure.

Thank you again. This is very helpful.

Hi mmp,

I agree with gardengal, and baking soda (sodium bicarbonate) would be harmful as a soil additive. If you want to treat your soil, there is some clear plastic sheeting that you can spread on your soil. That clear sheeting will heat the soil in bright sunshine to kill disease germs near the surface, as well as harmful insects. The earthworms will simply go deeper to avoid being harmed. As gardengal suggested, remove and discard affected plant parts. Incidentally, I also bag and discard my old zinnias in the trash.

ZM

Great! Thanks for the suggestion.

the plants created a dead air zone that was dark.. which encouraged the PM ... once you remove the plants.. air movement goes up ... and sun takes care of the rest ..

a corollary to this would be.. there is no reason not to throw it all in the compost pile.... you didnt need to hermetically seal it and send it to the dump ...

dont make all this harden than it need be ..

ken

Thanks, Ken. I can empty the bags in the field then. Sounds good.

"That clear sheeting will heat the soil in bright sunshine to kill disease germs near the surface, as well as harmful insects. The earthworms will simply go deeper to avoid being harmed."

What about ground-dwelling bees and the ilk?

If you are dealing with annuals - like the zinnias or most veg crops - I wouldn't bother with the plastic. As long as you clear up all plant debris, there is nothing for the PM spores to overwinter on. So any solarization (which is not very effective in winter anyway) is unnecessary and so no danger to soil dwelling beneficials.

Even with perennials and woody plant material, where above ground parts may remain intact all winter, there is no certainty that PM will return the next season. Good garden sanitation (a thorough fall clean up) will generally prevent a recurrence unless a particularly susceptible species. Among annuals, zinnias and cucurbits are quite prone; monarda, garden phlox, peony and many composites with perennials and lilac, ninebark, dogwood and Malus species (apples and crabapples) with the woodies.

The good news is that PM is typically more of a cosmetic issue than one that is overly harmful, although it can weaken annuals to the point where they fail to thrive and lose enough foliage to impact photosynthesis.

Thanks. I’ll skip the plastic. Glad to hear this isn’t something i need to be overly concerned with. The provlem seems to already be remedied. Thank you for all the help!

And the plastic doesn't work in all climates. In mine weeds and bugs would just think you’ve given them a greenhouse and grow even lustier.

Hi all,

I agree, the plastic is optional. I do plan to apply some myself, more as an experiment than as something that has to be done. If I see any ground-dwelling bees, I will not apply plastic over them.

ZM