Hi, I've grown some beautiful petnias in various pots. They were separated in different parts of the garden, but each has got quite severe pests, leaving the flowers, buds, and sometimes leaves severely bitten or snipped off. The worms look like caterpillars, mostly white, a few being dark reddish. I've manually killed about 20 of them that I could see over the past 2 days, but I still see many many small roundish stuff attached to flowers or branches--are they larva? These small roundish stuff are about 5mm in diameter, with the center being yellowish and two sides quite transparent.

I also only saw these worms on petunia, not on other flowers planted in the same containers mixed with petunia.

Please help! Thank you!

Hi, There are many caterpillar pest of bedding plants so I can't say for sure what this one is based upon the description plus I am not familiar with what might be a pest of petunia in California. However, most leaf feeding caterpillars are easily controlled with Sevin ith they are damaging. As far as the rounded material they could be eggs or they might even be fecal matter left behind by the caterpillars as they feed.