health of nearby plants, cover crops, chop and drop material

Hello,
,
I am just looking for general ideas about plants that appear unhealthy, be they veggies, nearby landscaping plants, cover crops, or potential chop and drop material.

For example, a patch of wild bergamot (Monarda fistulosa) is near a potential new veggie bed location and has powdery mildew or something similar.  Is this a potential risk to spread to the veggies?   Mondarda is subject to this type of thing and the plants otherwise are growing well.   What should I do about this?   Ignore?  Try to treat the monarda or soil?  Alternately I could move/remove the Mondarda I suppose.   I could limit that bed to certain non-susceptible veggies.

Related, for chop and drop, how picky should I be regarding outward appearance and health of the weeds being dropped?  For instance, consider discolored clover leaves (likely due to heat stress and competition), or late season dandelion that is quite battered.

I have read suggestions that veggie plants showing unhealthy signs should be disposed of in the garbage, but that seems a bit extreme to me.  Any thoughts on how to think about plants showing blight, disease, decay, or stress near veggies are appreciated!

Thanks for any ideas or musings, as I don't have much experience with food crops.

I really only worry about using visibly ill plants in the case of moldy cucurbits or tomatoes, where I`m worried about mildew spores getting transmitted onto healthy plants. Those I will actually bag up and put in the trash, much as I hate to do it (can't burn here in the city without ticking off my neighbors).
I don`t worry about any other plants that have problems (I get rust on some allium species, aphids everywhere depending on rainfall, bean beetles, etc.) It all makes great mulch.

Getting rid of powdery mildew is easier than getting rid of the plant that has it.

A really good treatment for powdery mildew is: 1 gal water, 1 T dish soap, 1 T baking soda.

I put it in a spray bottle to make applying it easy.

Some recipes call for adding oil. I have never found a need for the oil.

I have also found that some plants get powdery mildew while plants next to it don't.

@Anne Miller thanks for sharing this recipe!  I have powdery mildew on a susceptible maxima (Marina di Chiogga) pumpkin and I was out there spraying it with compost extract today.  I will give this recipe a try and will share it with the gardeners I guide. it seems so simple!