Systemic insecticides injected into tree trunks work by absorbing into the tree’s vascular system and repelling pests from the inside out. You can use this type of insecticide for a wide range of pests, including borers, aphids, leaf miners, whiteflies, thrips, and soft-scale insects. The best time to inject trees with systemic insecticides is in late spring or summer, when the trees are in full leaf. Try to perform the injection when the soil temperatures are at least 45 degrees Fahrenheit and the weather is humid or rainy. Also, you’ll need to know the tree trunk’s diameter at a certain height to calculate the dosage for the systemic insecticide injection.

1、Water the tree thoroughly for at least two weeks prior to injecting the systemic insecticide. Perform two to three deep watering sessions per week.
2、Measure the circumference of the tree trunk in inches approximately 4 ½ feet up from the ground. Wrap rope or string around the tree trunk, mark where the string overlaps or meets and then measure the string or rope to the mark.
3、Divide the measured circumference of the tree trunk by three to calculate the diameter at “breast height.” For example, if your tree trunk has a circumference of 36 inches, the diameter at breast height would be 12 inches (36 inches / 3 = 12 inches).
4、Calculate the correct injection dosage of systemic insecticide based on the tree’s diameter at breast height and the type of insect that is threatening or infesting your tree. Follow the manufacturer’s instructions on the label exactly.
5、Pre-drill injection holes into the tree bark at the base of the trunk near the ground, using the appropriate size drill bit recommended by the insecticide manufacturer. Drill the number of holes needed for the recommended dosage through the bark and about 5/8ths of an inch into the sapwood.
6、Inject the systemic insecticide into the pre-drilled holes in the tree trunk. Follow the directions on the label exactly.

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