Q. I had two planters of petunias that stopped blooming and the leaves had lots of little holes. You told me that Tobacco Budworm was at fault and suggested applying Dipel or Thuricide. After several applications we had lots of blooms on the petunias. At the end of this growing season should we replace all of the potting soil in the planters with new soil in the spring? Many thanks!
A. This insect can survive here through the winter in the soil. If these are potted plants then you can replace the soil but cultivating the soil several days before planting will help to expose them to birds.
I would watch for this problem in the future. These insects have wings in their adult form so they will fly into your flower bed from the neighbors. The two things to look for are the holes in the leaves and those little black specks which is budworm poop.
Next year in May or June start looking for that on your petunias and other susceptible flowers. I would not give up on petunias and Nicotiana just because of budworm. Put down a couple of protective sprays of Bt, Spinosad or any synthetic pyrethrin spray in April and May.
The fact that you put down Bt (Dipel or Thuricide) and had a reduction in the past problem tells me that it is working for you. Next year switch to Spinosad. The year after that use a permethrin spray. The year after that switch back to Bt. Keep rotating your pesticides.