Is there a systemic chemical to use before an attack on arborvate?
New Castle County Delaware bag worms
No there is not. The best plan of action is to watch for bagworms starting around the first week of June. They are very small at this stage of the year. Mid- to late-June they are still relatively small but easier to see/find on the tree. Anytime from mid- to late-June an application of Bacillus thuringiensis kurstaki or spinosad can provide excellent control. Neither are systemic. There are no homeowner products that are systemic available and the professional products that are available are very expensive but provide no better control than the two already mentioned. If you need to make an application earlier in the summer than mid-June you won't have a problem seeing the numbers of bagworms present and you can treat with the previously mentioned products and obtain excellent control. You can physically remove any bags now, and greatly reduce the number of potential bagworms this year because you'll remove the pest before they hatch out of the eggs laid by the female last fall. There is no preventative systemic treatment for bagworms.