Might you be able to post clear photos of the "charcoal dust"? If there is sufficient humidity, and there are overhanging limbs from plants which have aphids, spider mites or other sucking insects on their undersides, the "honey dew", sugar water, from their sucking, drips down on to the upper leaf surfaces below the leaves where they're feeding. There is a mold, called, "Black Sooty Mold", which grows in the honey dew. Or, it could actually be soot from exhaust. Perhaps a diesel vehicle idled near enough to it for some of the soot from the exhaust to settle on it? Will the soot blow off the leaf or is it greasy?

Your Gourmet Popcorn issue sounds like the beginning of chlorosis, iron and nitrogen deficiency. You may need to feed again. If it's not warm enough for the organics to break down fast enough and if there is excessive rain or other irrigation, the nitrogen gets flushed through the soil, leaving the plants deficient in it. You can also green up that growth by using inorganic fertilizers or increase the heat if it's been overly cool/cold by placing hard scape (stepping stones, large rocks, etc.) near the plant to absorb and radiate heat from the sun. It all depends upon why the plant is growing faster than the nitrogen/iron are available. Kim

My Gourmet Popcorn also sometimes has the pale green leaves problem and I also often use organic Plant-tone. I tossed on and watered in an extra small handful of non-organic Osmocote with a high nitrogen level in it. I'm thinking it was nitrogen 19, and the next two numbers something like 8 and 9 (maybe even lower). You have to check the different Osmocotes to find the one with nitrogen 19.

Another time I lightly scattered and watered in some really high nitrogen grass food--the nitrogen up there in the 20s and the other numbers something like 2 and 3.

I think that fixed the problem--at least I don't remember having that problem with Gourmet Popcorn in the past year.

Good luck.

Kate

If there is a contrast with darker veins, it is iron deficiency. (Nitrogen deficiency will also occur if you never fertilize.)

Smog is one possibility in this dry dusty drought-stricken state.

Another would be the mold that forms on the honeydew aphids leave behind.

If it washes off easily with a blast from the hose, it's the first. If it doesn't, check for ants and aphids.

Washing off the foliage every couple of weeks in summer where there is no summer rain yields a much prettier garden. The plant's leaves can respirate better and it reduces stress on them. It doesn't take that much water if it is done carefully.

Roseseek, there WAS a diesel vehicle idling by the bush this week!!! I suppose if the leaves are sticky, they can pick up the exhaust.

There was a vinca bush near the roses that was horribly infested with...what, aphids, white flies? When I yanked it I noticed stuff flying in the air, gnats or dusty stuff, not sure. Left a greasy mark on the pavement it had grown over. I sprayed the rose bush with water which didn't do much unless I rubbed the wet leaf between my fingers. It's on the old growth, not the newer growth. We'll see how it goes now that the vinca is gone.

Thanks everyone.

It's been a bad year for white fly here, too. Getting rid of the vinca should help relieve the water stress caused by the competition and eliminate their habitiat. I would turn on the hose to a trickle and wash all the yuck off the rose foliage. It will rehydrate the rose and help prevent the diesel from destroying those leaves. If you put down your fertilizer before you wash the foliage, you can kill two birds with the same stone...cleaning the foliage and watering in the food. Good luck! I'm glad it appears it was something simple. Kim