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Systemic Insecticide Treatments

The following is adapted from the University of California's excellent integrated pest management website:

Imidacloprid is not effective against the nation's widespread pine bark beetle infestation. Foliar treatments with cypermethrin repel beetles during their swarming phase and can protect a tree for about a month. Repeated applications are necessary for long-term protection. Photo Courtesy of Ronald F. Billings, Texas Forest Service,

The streets of downtown Sanford, Fla., are lined with historic buildings, many dating from the late 19th century. The Girard Companies headquarters are in Sanford and currently employ about 200 full-time employees.Imidacloprid is a systemic pesticide that provides months-long protection for trees. The substance has proven effective against a range of insect troublemakers, including emerald ash borer, Asian longhorned beetle, the eucalyptus lerp psyllid and others.

Professional-strength imidacloprid is sold under the trade names Imicide and Merit. Certain formulations of the chemical (Bayer Advanced Garden Tree & Shrub Insect Control and Pointer) are available to the home gardener. Only limited research has been conducted on pesticide efficacy, and it is not known why some users report good control with this insecticide while others find results to be disappointing.

Systemic insecticides are available for application into trunks or roots or by spraying foliage. Imidacloprid is also available to both home gardeners and professionals for application on or into soil beneath trees. When using systemics, whenever possible consider making a soil application instead of spraying foliage or injecting or implanting trees. Injecting or implanting trunks or roots injures trees, and it is difficult to repeatedly place insecticide at the proper depth. Avoid methods that cause large wounds, such as implants placed inside large holes drilled in trunks. Do not implant or inject roots or trunks more than once a year.

Imidacloprid may be effective when applied to soil during late winter to early spring or before rainfall or irrigation are expected to facilitate root absorption of the insecticide. Summer application to stressed, heavily infested trees is less likely to be effective and is not recommended. Consider treating only those trees where the pest has been intolerable or tree health appears threatened by insects. Insecticides will adversely affect any beneficial parasites, so leave at least some nearby untreated to facilitate potential biological control.

Foliar sprays generally are not recommended. There are no selective insecticides that kill only psyllids. It is difficult to spray large urban trees without a pesticide drifting off-target. The lerp helps protect psyllid nymphs from spray contact.

Injectors like these Mauget capsules send imidacloprid to the tissue layer under the bark, where it is transported up to the rest of the tree. An alternate method is to apply the pesticide to the root area by injecting it into the ground. Photo Courtesy of David Cappaert,

Handle Pesticides Carefully

Pesticides are poisonous. Always read and carefully follow all precautions and safety recommendations given on the container label. Store all chemicals in the original labeled containers in a locked cabinet or shed, away from food or feeds, and out of the reach of children, unauthorized persons, pets and livestock. Consult the pesticide label to determine active ingredients and signal words.

Pesticides applied in your home and landscape can move and contaminate creeks, lakes, and rivers. Confine chemicals to the property being treated and never allow them to get into drains or creeks. Avoid drift onto neighboring properties, especially gardens containing fruits or vegetables ready to be picked.

Do not place containers containing pesticide in the trash or pour pesticides down sink, toilet, or outside drains. Either use the pesticide according to the label until the container is empty, or take unwanted pesticides to a Household Hazardous Waste Collection site. Contact your county agricultural commissioner for additional information on safe container disposal and for the location of the Hazardous Waste Collection site nearest you. Dispose of empty containers by following label directions.

Tree Facts

1960 - Year the microbial insecticide, Bt, was first produced and sold as an insecticide. Bt is used to kill caterpillars of moths and butterflies.

3/8 to 1/2 -Ideal length, in inches, of the caterpillars when Bt application should begin. Bt can also be applied when tree leaves are one half of their full size.

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June 17, 2019, 8:31 am PDT

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