Question
I have several red barberry shrubs that have been losing their leaves shortly after blooming in the spring.  They develop a milky white discoloration and then fall off.  

I had contacted our local agriculture agent and he recommended spraying for bagworms.  This has not been effective.  

I have sprayed with insect sprays which were supposed to kill everything.  This has been ineffective.

Do you have any idea what could be the cause?  My guess is some kind of fungus.

Thank you for any reply.

Answer
Dear Joe, I think you are much closer than the agricultural agent.  In the first place, do you SEE any bagworms?  If you do, then it's bagworms; if you don't, then it's not.  In addition, bagworms are one of the the trickiest critters to spray for, because the female bagworm is secure in her bag and unaffected by what you spray on the tree and the male isn't even there as he flies around.  Then when the young hatch inside the female's bag, they spend a short time crawling around before they make bags of their own.  Therefore, timing is critical, because you have to get them while they are out of the bag, and hand control is very effective unless they are just covering the tree.  But we're not talking about bagworms because that isn't what you have.  What you have is powdery mildew, a fungus which makes a white film on the leaves and then they fall off.  Get some horticultural oil (SunSpray is my favorite) and spray the entire shrubs on a sunny day and within a few hours the mildew will start to dry and flake off.  You may need to spray a few times several days apart to completely get rid of it.  You can probably prevent this in future by spraying with NEEM which is an organic anti-fungal and works well on a number of things.  Be sure not to water at night, only morning or mid-day to prevent the disease from building up in the cooler night hours.  Anyway, you should be able to get this cleared up pretty quickly.  Let me know if you need further assistance.  Good luck, Melissa