Effective control for potato beetles and sawfly(Hibiscus/Datura)
Was at a client's home yesterday and noticed that the new branches from his large non tropical perennial Hibiscus had a lot of leaves towards the bottom half of the plants that were covered with holes. Some were so badly eaten that over 95% of the surface area of the leaf was gone! This type of Hibiscus sees its stems die each fall and new ones grow back beginning in mid May. So these stems have only been up for maybe 3-4 weeks, and many of the lower leaves are chewed up, but I didnt notice any of this damage just 11 days earlier. I looked closely at the leaves, and found very small, short worms/caterpillars here and there, and they correspond with the holes in each leaf. Some are 3/4" long, others are only 1/4" long, so they must be freshly hatched. Its amazing how fast they do damage. I looked them up and found that they are sawfly larvae(worms).
next I was looking at the zillions of seedlings popping up from last year's Datura plants, and as I was pulling them I saw holes in these leaves too, but didnt find worms on them even though they are right beside the Hibiscus. Instead I found potato bugs here and there. I recognized them from a potato garden I worked in in the 80's. They look like small beetles with yellow and black vertical stripes down their backs. When I looked this up on the internet, I saw that Datura are actually in the potato family, which tells me why potato bugs are nearby.
So I could take the easy route and use Imidacloprid because of its systemic properties, but I have read that it causes problems for honeybees and bumblebees, and may also kill the new baby praying mantis' that I have been trying to help to colonize every bed on this property.
What can I use that will control both potato bugs and sawfly larvae worms that wont need to be re-applied every 5-7 days and will reliably kill these things or encourage them to leave?