River Birch Sawfly Larvae – Proper Control
Q: In March I drenched the ground around our two river birches with the Ortho product which has imidacloprid. Each tree has 3 trunks, each about 6 inches in diameter. I used a 40 oz. bottle and divided it between the two. We have had no problem with sawfly larvae until mid-August, when I saw them eating leaves on the lower branches. Why didn’t the systemic stuff give protection for the complete season?
A: I don’t think you used enough product. If a trunk is 6″ in diameter it is approximately 19″ around. Three trunks equals 57″ around. Two similar trees equals 114″ of trunk circumference.
The label on the product says to use 1 oz. per inch of distance around the trunk. So you need 114 oz. of product, approximately three 40 oz bottles.
Now when your kids ask “Why do I need to learn this math?” you can give them an answer!