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Insecticides A Systemic By Erik Gab be y s our understanding of pest control has progressed, the number of tools available has grown considerably. Whereas arborists once had only sprays and saws as tools, they now have soil-applied systemics, systemic bark sprays,and trunk and root injections. Benefits of systemic insecticides include a broad range of uses, ease of application, complete canopy coverage, and limited environmental exposure. This is possible because of the way these insecticides work: Systemic insecticides use the tree's own vascular system to move the chemical throughout the above-ground trunk, limbs, and leaves.As a result, when applied cor- rectly, the chemical reaches even the highest leaf, something that is difficult to manage with spray applications. Soil application Soil application is efficient, inexpensive, and also very useful for large trees that would be hard to spray.There are two soil applica- tion methods: soil injection and soil drench. Both are efficient at moving the treatment to the active roots of the tree for uptake. Soil injection can be useful when treating a large number of trees at a site, whereas soil drench may be best when treating a small number of trees. Several types of soil injectors exist, and each administers a different volume of solution. Some of the most commonly used are large-volume hydraulic injection devices, like those currently used for fertilizer applications.The chemical is injected around the base of the tree to a depth of 3 to 6 inches, and is taken up by the tree's root system. Basal soil drench is applied by first preparing the solu- tion in a 5-gallon bucket.Then the top 6 inches of soil around the trunk of the tree is excavated and mounded to form a trench.The solution is poured in the trench, and the soil is returned. An alter- nate method is to follow the same basic drenching process, but skip the trenching step. Both of these applications can be done in approximately five minutes. Systemic bark spray For systemic bark sprays, an insecticide solution is sprayed on the bark of the tree using conventional spray equipment. Only the lower portion of the bark is sprayed — generally just the lower 4 to 5 feet of the trunk — unlike a foliar spray,which is used to cover www.arborage.com Examining the range of uses, ease of application, and other benefits Images provided by Rainbow Treecare Scientific Advancements the entire canopy.The product is absorbed through the bark and translocated, sometimes with the aid of a surfactant. Trunk and root injection Tree injections are slightly more complicated,and require an infu- sion system, but begin controlling insects almost immediately.There are several options on the market, but most work in a similar man- Arbor Age / November/December 2011 13 PLANT HEALTH CAREANT HEAL