What defines the spacing used in tree injections?

The correct choice emphasizes the practice of creating a discontinuous frill around the tree, and the application of small amounts of herbicide during tree injections. This method is important because it targets specific areas of the tree while ensuring that the herbicide is delivered effectively to the vascular system. By using small amounts, it minimizes the risk of harming the tree while promoting optimal absorption.

This approach allows for efficient use of the herbicide and can decrease the likelihood of adverse effects on non-target species and the surrounding environment. The use of discontinuous frills allows the applicator to control the dosage better and manage the injection process more carefully, leading to improved efficacy in pest control and plant management.

In contrast, continuous frills may lead to excessive herbicide application and increased risk of tree damage. Wide gaps between injections could result in insufficient herbicide distribution, and the practice of limiting it to a single injection can be ineffective for pest management, as it may not provide enough dispersion of the treatment throughout the tree.