Keeping the Legacy Alive

Chemical Control

Chemical pesticides are widely used as a primary defense against hemlock woolly adelgid (HWA) populations in the US. Chemical control can delay adelgid impacts, essentially providing a ‘life support’ for the trees and allowing more time for nature to adapt and for the development of longer-term solutions. In the US, it has been the most successful short-term method available for protecting high-value hemlock trees and slowing the spread of HWA. Chemical treatments to save trees may take as long as two years to translocate to the tree canopy where it becomes effective against HWA. A hemlock tree may lose capacity to translocate the chemical, and recovery will not be possible if treatment is not delivered early enough.  

Because HWA is protected by its woolly covering it is not effective to spray chemicals to control HWA.


Systemic insecticides have been applied by stem injection, basal bark application, and soil injection. Systemic insecticides are chemicals that are carried in the cells inside the tree that transport water from the roots to foliage. Currently there are four insecticides approved for use in Canada through Health Canada’s Pest Management Regulatory Agency – they include: IMA-jet, Xytect 2F, TreeAzin, and Starkle 20SG.  IMA-jet and TreeAzin are injected directly into the tree using special tree injection equipment, and Xytect 2F and Starkle 20SG are applied on the bark to the lower part (1.4m) of the tree using a backpack sprayer. IMA-jet and Xytect 2F take 6-9 months to take effect and provide 4-7 years of protection. TreeAzin and Starkle 20SG act quicker and only take 1 month to take effect, but only provide 1-2 years of protection. These are all commercial pesticides requiring a provincial pesticide applicators certificate ((Pesticide Applicator Certification | Pests and Pesticides ( to apply. There is no domestic or over the counter pesticide currently available for HWA control in Canada.Direct, systemic injection into trees greatly decreases environmental exposure to the chemical as well as total product amounts required.


To inquire about chemical treatment for hemlock on your property please contact a licensed applicator. Contact list will be up-dated as more licensed applicators become available.


Scott Robinson
Cell: 902-875-7686

Less toxic control products

Insecticidal soaps and horticultural oils have been used instead of insecticides. They have a low toxicity and have been effective when properly applied. Multiple applications are required and thorough coverage on larger trees is extremely difficult. Horticultural oils function by suffocating the adelgid; infested needles and well-protected waxy ovisacs must be completely drenched. Traditional pyrethroids (an organic compound found in the majority of household insecticides) and other pesticides are considered less effective than systemic insecticides because of the difficulty in achieving adequate coverage and the larger amounts required for external spray applications, greatly increasing the toxicity exposure to other organisms. Other less toxic insecticides are also being tested by CFS.


Please carefully consider the options available and consult with a professional certified pesticide operator if you decide to use neonicotinoids to help keep hemlock alive and mitigate the spread of HWA on your property.



Risk Assessment of Imidacloprid use in forest settings on the aquatic macroinvertebrate community.


Environmental Risks to Arthropods from Imidacloprid Applications for Hemlock Conservation. 

Emergency Registration of Starkle 20 SG for control of hemlock woolly adelgid in Nova Scotia

2022-4763 2022-10-27 FOR EMERGENCY USE ONLY For sale and use in Nova Scotia from October 27, 2022 to October 26, 2023. STARKLE 20 SG Water Soluble Granules For application as a basal bark spray for control of Hemlock Woolly Adelgid on hemlock. For Use in Forests, Woodlands, and Other Treed Areas. RESTRICTED KEEP OUT OF REACH OF CHILDREN READ THE LABEL BEFORE USING REGISTRATION NUMBER 34653 PEST CONTROL PRODUCTS ACT CAUTION – EYE AND SKIN IRRITANT ACTIVE INGREDIENT: Dinotefuran ........................................................... 20.00% Net Contents: 5.7 Kg Warning, contains the allergen milk IN CASE OF EMERGENCY INVOLVING A POISONING OR MAJOR SPILL CALL +1 202 464 2554 Manufactured for: Canadian Agent: Belchim Crop Protection Canada Inc. 104 Cooper Drive, Unit 3 Guelph ON N1C 0A4 1-866-613-3336 NOTICE TO USER: GROUP 4 INSECTICIDE MITSUI CHEMICALS AGRO, INC. Nihonbashi Dia Building, P. O. Box 5126 1-19-1, Nihonbashi Valdosta, GA 31603-512


This pest control product is to be used only in accordance with the directions on the label. It is an offence under the Pest Control Products Act to use this product in a way that is inconsistent with the directions on the label. NATURE OF RESTRICTION: This product is only to be sold to and used by individuals holding an appropriate pesticide applicator certificate or license recognized by the provincial/territorial pesticide regulatory agency where the pesticide application is to occur. This restriction applies to all basal trunk spray handlers. In Nova Scotia: only by registered pesticide applicator with Class III (A) Forestry or Class III (D) Landscape license For applications in other treed areas: Treatments is such areas must be first recommended by qualified federal or provincial government licensed professional staff (Natural Resources sector). DIRECTIONS FOR USE As this product is not registered for the control of pests in aquatic systems, DO NOT use to control aquatic pests. DO NOT contaminate irrigation or drinking water supplies or aquatic habitats by cleaning of equipment or disposal of wastes. FOR USE AS A BASAL BARK SPRAY FOR CONTROL OF HEMLOCK WOOLLY ADELGID MIXING INSTRUCTIONS: Add ½ of the required amount of water to the mix tank. With the agitator running, add the desired amount of STARKLE 20 SG to the tank. Continue agitation while adding the remainder of the water. Begin application of the solution after STARKLE 20 SG has completely dispersed into the mix water. APPLICATION PROCEDURES AND SPRAY EQUIPMENT Basal trunk spray using backpack sprayer. Apply with low pressure sprayer operated at maximum 20 PSI to avoid splash-back and drift. CROP PEST PRODUCT RATE PER APPLICATION SPECIAL INSTRUCTIONS Hemlock Hemlock Woolly Adelgid 67.5 g of product per litre of water (13.5 g of active ingredient per L of water) When applied just to the point of runoff, 3.78 L of spray solution should treat approximately 1.6 to 2 m of cumulative trunk diameter (calibrated flow rate should deliver 44 – 60 mL of spray solution per 2.5 cm of trunk diameter for suitable coverage) or 5 L of spray solution should treat approximately 2.1 to 2.8 m Spray solution on bark over entire circumference of tree trunk from 10 to 135 centimetres (4-54 inches) above the soil surface. Wet bark with spray solution to the point of saturation and before run off. During application do not allow spray solution to run off trunk on to soil surface. Do not apply directly to soil . Apply when hemlocks are actively growing and transporting water in xylem (MarchNovember). In actively growing hemlock, control may be evident within 2 weeks after application. RESTRICTIONS: - Maximum one application per year - Maximum 3025 grams Starkle 20SG per hectare per year (605 g of active ingredient per ha per year) In some cases, tank mixing a pest control product with another pest control product or a fertilizer can result in biological effects that could include, but are not limited to: reduced pest efficacy or increased host crop injury. The user should contact Belchim Crop Protection Canada Inc. at 1-866-613-3336 for information before mixing any pesticide or fertilizer that is not specifically recommended on this label PRECAUTIONS KEEP OUT OF REACH OF CHILDREN May irritate the eyes and skin. Avoid contact with skin, eyes, or clothing. Wash thoroughly with soap and water after handling. Keep children or pets off treated area until spray is dry. Wear a long-sleeved shirt, long pants, chemical-resistant gloves, socks and shoes during mixing, loading, application, clean-up and repair. Follow manufacturer's instructions for cleaning/maintaining personal protective equipment (PPE). If no such instructions for washables exist, use detergent and hot water. Keep and wash PPE separately from other laundry. Wash hands before eating, drinking, chewing gum, using tobacco or using the toilet. Remove clothing immediately if pesticide gets inside. Then wash thoroughly and put on clean clothing. Remove PPE immediately after handling this product. Wash the outside of gloves before removing. As soon as possible, wash thoroughly and change into clean clothing. Apply only when the potential for drift beyond the area to be treated is minimal. Take into consideration wind speed, wind direction, temperature inversions, application equipment, and sprayer settings. DO NOT enter or allow worker entry into treated areas until sprays have dried. DO NOT use in residential areas unless a restricted entry interval of 96 hours can be enforced (signs must be posted and area must be marked off). Residential areas are defined as any use site where bystanders or the public, including children, could be exposed during or after application. This includes areas in and around homes, schools, public buildings or any other areas where they could be exposed. FIRST AID IF SWALLOWED: Call a poison control centre or doctor immediately for treatment advice. Have person sip a glass of water if able to swallow. Do not induce vomiting unless told to do so by a poison control centre or doctor. Do not give anything by mouth to an unconscious person. IF ON SKIN OR CLOTHING: Take off contaminated clothing. Rinse skin immediately with plenty of water for 15 to 20 minutes. Call a poison control centre or doctor for treatment advice. IF INHALED: Move person to fresh air. If person is not breathing, call 911 or an ambulance, then give artificial respiration, preferably by mouth-to-mouth, if possible. Call a poison control centre or doctor for further treatment advice. IF IN EYES: Hold eye open and rinse slowly and gently with water for 15 to 20 minutes. Remove contact lenses, if present, after the first 5 minutes, then continue rinsing eye. Call a poison control centre or doctor for treatment advice. Take container, label or product name and Pest Control Prroduct Registration Number with you when seeking medical attention. TOXICOLOGICAL INFORMATION: No specific antidote is available. Treat the patient symptomatically. ENVIRONMENTAL PRECAUTIONS Toxic to aquatic organisms. Toxic to bees. Hemlock trees are not attractive to pollinators. However, bees may be exposed through direct spray, spray drift, and residues on/in leaves, pollen and nectar in flowering crops and weeds. Minimize spray drift to reduce harmful effects on bees in habitats close to the application site. Avoid applications when bees are foraging in the treatment area in ground cover containing blooming weeds. Toxic to certain beneficial arthropods (which may include predatory and parasitic insects, spiders and mites). Minimize spray drift to reduce harmful effects on beneficial arthropods in habitats next to the application site. STORAGE: Store this product away from food or feed. Store in a cool, dry place and in such a manner as to prevent cross contamination with other pesticides, fertilizers, food, and feed. Store in original container and out of the reach of children, preferably in a locked storage area. DISPOSAL: DO NOT reuse this container for any purpose. This is a recyclable container, and is to be disposed of at a container collection site. Contact your local distributor/dealer or municipality for the location of the nearest collection site. Before taking the container to the collection site: 1. Triple- or pressure-rinse the empty container. Add the rinsings to the spray mixture in the tank. 2. Make the empty, rinsed container unsuitable for further use. If there is no container collection site in your area, dispose of the container in accordance with provincial requirements. For information on disposal of unused, unwanted product, contact the manufacturer or the provincial regulatory agency. Contact the manufacturer and the provincial regulatory agency in case of a spill, and for clean-up of spills