As of 2015, there are four insecticides registered in Canada for use for emerald ash borer (EAB). All are systemic insecticides that must be applied with a series of trunk injections or implants. The list of registered pesticides and their labels can be found by searching the Pest Management Regulatory Agency (PMRA) database.
- TreeAzin™ Systemic Insecticide (active ingredient azadirachtin) is the most widely used at this time, and has shown good success in scientific trials, with limited environmental effects[47,48]. TreeAzin, produced from extracts of neem tree seeds, is injected directly into the tree's vascular system where it is taken up by the tree and enters all of its tissues. It kills EAB larvae feeding on tree tissue by altering larval growth (disrupts molting) and preventing the insect from developing[44,45]. Adult females feeding on leaf tissue of treated trees also show reduced fertility (the number of eggs laid) and fecundity (the number of eggs produced). Treatment must be repeated every two years until the tree is not longer threatened by EAB. Injections are done by a licensed TreeAzin™ applicator.
- Confidor® 200 SL Systemic Insecticide (active ingredient imidacloprid) is a neonicotinoid insecticide that works on the nervous system of the insect, over-stimulating it and killing it. The pesticide label for Confidor states that it may only provide suppression of EAB. There is a lack of published experimental work on treatment for EAB with this pesticide to demonstrate its effectiveness. Research in the U.S.A. using Imicide, another imidacloprid-based insecticide, shows variable and inconclusive results[47,48].
- IMA-jet (active ingredient imidacloprid), using the same active ingredient as Confidor, has a similar effect on the insect nervous system. Early trials show IMA-jet to be more effective than other imidacloprid-based products, perhaps because it also contains a higher dosage of active ingredient than these other products. Results from these trials show that treatment in late May reduced numbers of both EAB larvae and adults, and July treatments reduced larvae. However, late treatments were more effective in larger trees than smaller ones . IMA-jet treatment needs to be repeated yearly to remain effective .
- Acecap® 97 Systemic Insecticide Implants (active ingredient acephate) is an organophosphate that works by blocking an enzyme, which stops the insect's nerve signals from being conducted. The label advises that it reduces populations of EAB larvae and reduces their damage, but may not provide control of it. As with Confidor, there is no published research on this product and its efficacy for EAB yet. Treatment with AceCap should be done between early April and early June and must be repeated yearly since it optimal control period is 10-12 weeks. Relatively large holes need to be drilled into the tree for the implants to be inserted (9.5 mm) and this, along with the yearly treatment required, may cause structural weakness in the tree.
Insecticide treatment is more likely to be successful if started before the tree is infested, or when infestation is at a low level - trees with vascular tissue compromised by feeding of EAB larvae may not respond to treatment. Treatment should be done when the tree is actively transpiring in order for insecticide to be taken up effectively by the tree. The effect of these insecticides on pollinators is unknown but currently not thought to be of great concern - more on pollinators and EAB pesticides.
Selecting trees for treatment:
Some criteria for selecting trees for treatment used by municipalities and other landowners:
- Tree health: declining trees may already be infested with enough EAB to compromise treatment. Trees with >25-30% foliage loss are typically not chosen for treatment.
- Structural integrity: trees with risk of failing are better replaced than treated.
- Size of tree: it may be more feasible to remove and replace smaller trees (<20 cm diameter at chest height) rather than treat them. There is anecdotal commentary that smaller diameter trees may not tolerate repeated injections or may not take up insecticide efficiently.
- Location: trees that will need significant management because of obstructions (too close to sidewalks, roads, utility lines etc.) may be better replaced than treated.
- Ash density/impact of EAB: areas with a high proportion of ash will suffer greater environmental and aesthetic impacts from EAB so may be priorities for treatment.
- High profile, heritage or memorial trees may be priorities for treatment.
- Crown volume/relative shade value: in parks and playgrounds, trees with greater relative shading value may be priorities for treatment.