Soil drenching is the process of adding diluted control products directly to the base of a plant. It provides deep, targeted treatment and is a useful way for professionals to apply insecticides to trees with pest infestations. It also can be a way to apply fertilizers to plants with specific nutrient needs. During a soil drench, the product is poured directly over a plant’s roots near the stem or trunk. This method allows the applicator to prevent the chemical from contacting other plants.
Soil drenches often take effect slowly because the chemicals need time to be absorbed by the roots and spread to the stems, branches and leaves. That’s why the best time to apply a soil drench is early in the growing season. It’s also important for tree and shrub care professionals to apply a soil drench when the plant is well hydrated, as the chemicals will spread through the plant more efficiently if water is already moving through its system.
Before applying a soil drench, first correctly identify the target pest and select the appropriate product. Read the product label to understand safety precautions and determine treatment timing. Always follow state regulations regarding applicator licensing.
Follow these steps to apply a soil drench to a tree or a group of trees safely and correctly.
Step 1
At 4.5 feet above the ground, wrap a measuring tape around the trunk of the tree. Divide the measurement by 3.14 to get the tree’s diameter at breast height (DBH). Use these guidelines to determine the DBH for a tree with multiple stems.
Multiple individual trees growing in close proximity: For trees that have grown close together, measure the DBH of each stem and treat each stem individually.
Multistem spilt at or below DBH: For a tree that has multiple stems splitting below DBH, measure the tree at the narrowest point between the root flare and the split.
Stem clusters: For trees that are grown too close together to be treated separately, measure the DBH of each stem and add the measurements together.
Step 2
Dig a trench around the base of the tree that’s 2-3 inches deep and 4 inches wide. Dig deeper if there is potential for runoff or if the soil is heavy clay or compacted.
Step 3
Using the DBH, refer to the product’s label to determine how much is needed and follow the label’s mixing instructions. Apply the product by pouring it evenly around the tree inside the trench. After the product has been completely absorbed by the soil, firmly replace the excavated soil into the trench.
Source: The Tree Geek, thetreegeek.com
Illustrations: David Preiss
