2 Fridays ago I noticed definitely some bugs were eating/chewing leaves on my roses, clematis, and dahlias. Early in the season I was using Rose Rx by Bonide. A neem oil based insecticide, miticide, and fungicide. So I sprayed that thing that Friday evening. Late last week I was noticing some yellowing leaves on the roses and that triggered me to a 'panic mode' thinking I'm getting black spots on my roses, as I barely get any black spots at all. It did occur to me that Rose Rx should also work as a preventive measure for black spots. I find it strange that all of a sudden I got 'black spots'. I read the direction again and it says "repeat every 7-14 days". So last Saturday I sprayed again with the Rose Rx. Yesterday (Monday) I removed all the yellow/yellowing leaves in every rose bushes. Today, there were more yellow leaves that seems to appear overnight. So again I started to remove them and that's when I really noticed that they're not actually caused by black spots, but rather I might have done something wrong.

So I did some research and found my mistake. NEVER spray with an oil based product (natural or synthetic) when temperatures are constantly in the high 80's or over 90's as it will suffocate foliage on your roses. No. 1 symptom - leaves will turn yellow a few days after you spray them. Sure thing our temp were constantly in the high 80's for the past 2 weeks. Today we reached 91 and tomorrow will soar to 93. Lesson learned! Bonide at least should put a warning in their label.

My Green Light neem oil does warn against spraying during the heat of the day.

Well, lesson learned, lesson taught. Any day you learn something is always a good day! At least the stuff didn't kill the rose!

Porkpal - It did warn against spraying during the heat of the day. I sprayed late in the evening.

It didn't warn not to use the product if a 'heat wave' is expected for several days. Two weeks or so of temperatures in the high 80's and 90's was the underlying cause of leaves suffocating in oil.

Green Light also has no heatwave warning, but I sprayed my tomatoes recently and they seem okay despite 95 degrees minimum days and 80 at night. However it also cautions against using on sensitive plants including "some roses" - you must have those!

They should have been more specific then on their labels. With a name like 'Rose Rx', one would think it's the perfect prescription for roses.

That is why they named it "Rose Rx"! It has been extremely hot extremely early in the season this year. Blech.

Two years ago, I sprayed my plants with an all natural insecticide which damaged all of the leaves on my roses and peonies. Now I try anything new on the bottom few leaves of each type of plant, just in case. Been drowning Japanese beetles morning and night the past few days. I hate those things. They seem to like my Wildeve rose the best, so far. I am not certain if the systemic products I started using in my main rose bed this year have had an effect on the beetles. Time will tell.

My neems oil doesn't warn about using it in hot weather, either, but I read about it on a list last year. I did use a bit on the tips of my tiger lilies which were developing a fuzzy white fungus. They didn't mind.

Tomorrow will be cooler, a balmy 84'F, and I have lots to do outside. My viking constitution doesn't do well in the heat.

Thankfully the damage were minimal and mostly it were the older leaves that were yellowing, and just barely filled a 2-gal pot when I removed them from the more than 50 bushes I have. Today's high reached about 95 degrees but somehow the yellowing subsided.
We didn't get hit with the storm today, but because of that storm, temp went down by mid-afternoon and that helped too. Hopefully tomorrow will be a little cooler and less muggy.