A once a year systemic insecticide drench is applied ahead of insect activity, ideally in the fall or early spring when boring insects are the target, so the tree is protected throughout the growing season. The roots normally take about 3 weeks to carry the insecticide through the tree, and one application then protects it for a full year.

Why does a systemic drench need to be applied early?

Because the tree has to absorb it first. A systemic drench, an insecticide watered onto the soil and taken up by the roots, normally takes about 3 weeks to spread through the tree, so protection only begins once that uptake is complete.

When should a drench be applied against boring insects?

In the fall or early spring, protection is already in place for the growing season. To keep borers such as emerald ash borer out through the season, Once A Year Insecticidal Drench w/Merit is watered onto the roots during that window, at 1 oz of concentrate for every inch of trunk circumference measured at chest height.

When does a drench make sense for sucking insects?

When a tree has been attacked by sucking insects such as aphids and scale repeatedly over several years and a stronger treatment is needed. Because uptake takes about 3 weeks, the drench needs that much lead time before the insects return.

What if insects are already attacking the tree?

A trunk injection works faster, because a drench leaves the tree unprotected for the roughly 3 weeks its uptake takes. When a drench moves up from the soil, the Multi Insect Killer Tree Injection Kit is injected directly into the trunk and gets through the tree in about 72 hours.

Frequently Asked Questions

Does rain wash a systemic drench away?

No. Once applied, the drench gives systemic, rainproof protection.

Which part of the tree does the drench protect most?

New growth especially. The drench protects the entire tree or shrub, with new growth getting particular protection.

Can the drench be used on a palm or oak too tall to spray?

Yes. TreeHelp's palm and oak pages both point to the drench when a tree is too tall to spray.

Is the drench available everywhere?

No. It is not sold in New York State or Canada.