How do I get rid of these little black spots and bugs on my petunia plants. They are all over on stems and leaves. Turns my plants brown.
You don't give much to go on. Just a guess: bugs = aphids, black spots = sooty mold or other fungal pathogen
I've never used this on 'tunias, but I've used it on lots of other plants - try it on one stem first: 50:50 mix of 70% isopropyl (rubbing) alcohol:water with about 6 drops of dishsoap per quart. Soak leaves and stems, paying particular attention to undersides. This remedy has no residual effects, so you'll need to remain vigilant and treat at least once/week. If I was you, I would obtain some cold pressed neem oil and add it to the mix. Neem works slowly (takes 1-2 weeks to see full benefit of results), but is wonderful as an anti-feedant and a sterilizer (inhibits the metamorphic cycle) and is extremely safe.
I too had the same problem. I did a pretty intensive search on GW and this is what I came up with.
Here is a link that might be useful: Caterpillar dung
I have the same problem with my petunias. Here's what I my research lead me to...the answer!
Here is a link that might be useful: The Connecticut Agricultural Experiment Station
Although my earlier reply may be what you're experiencing, following more research, I think what you have are bud worms. In the link below, scroll down to the section that reads, "Let's start with the Tobacco/Geranium/Petunia bud worm" for more information.
Here is a link that might be useful: Weidners