The Emerald Ash Borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is an invasive wood-boring beetle that was positively identified in Boulder, Colorado in September 2013. Its native range is eastern Russia, northern China, Mongolia, Korea, Japan and Taiwan. The beetle’s first North American populations were confirmed in the summer of 2002 in southeast Michigan and in Windsor, Ontario. Judging by the size of the infestations and the stage of damage to the infested trees, the beetle was likely introduced to the area in the early to mid 1990’s. It is believed that the beetle was introduced into North America in ash wood used for shipping pallets and packing materials in cargo ships or shipping containers.
There are no natural controls for EAB in North America, and none of the domestically native ash (family Oleaceae, genus Fraxinus) trees have any resistance to EAB. Asian ash trees such as Manchurian ash are resistant, but all varieties of green ash, white ash, and black ash are susceptible to attack by this extremely aggressive pest. Mountain ash is not susceptible because it is in the rose family (family Rosaceae) and is not a true ash.
As of 2017, over 100 million ash trees have already been lost in infested areas throughout North America. If left unabated, EAB will kill every true ash in an infested area. The US Department of Agriculture and state agencies, including the Colorado Department of Agriculture have recently introduced parasitic wasps from Asia in some locations to try to control EAB populations. These parasitic wasps naturally control EAB populations in their native environments, but these trial releases have not had enough time to determine the effectiveness of these efforts.
The only known effective prevention for EAB damage at this time is chemical treatment of your ash trees. Walker Tree Care offers two treatment options. Both options are similar in cost per treatment.
TreeAzin is a systemic insecticide injected directly into the base of trees. It is produced from Neem tree (Azadiracta indica) seed extracts. This is not Neem oil. Neem extracts have been used for centuries to control insects. The active ingredient in TreeAzin is Azadirachtin (5% solution). TreeAzin is listed by the Organic Materials Review Institute (OMRI) for use in organic crops. TreeAzin is owned by the Canadian Forest Service (CFS) and was developed in collaboration with BioForest Technologies, Inc, who holds its worldwide license.
TreeAzin provides up to two years of protection against EAB, although annual injections may be required during high pest pressure periods. It works by interfering with the life states of EAB development rather than being acutely toxic upon contact. The main advantage to TreeAzin is that it is not persistent in the environment, and presents a low toxicity level to pollinators. If applied according to instructions, TreeAzin is approximately 90% effective against EAB.
Emamectin Benzoate is available under a couple of different brand names: ArbormectinTM and TreeAgeTM. It is a synthetically derived pesticide in the Avermectin family, and like TreeAzin is a systemic pesticide injected into the base of trees. Emamectin Benzoate is acutely toxic to all insects, and kills them upon contact.
Emamectin Benzoate provides two years of pretection against EAB regardless of pest pressure. However, it is persistent in trees for at least two years, and is extremely toxic to pollinators. If applied according to instructions, Emamectin Benzoate is nearly 100% effective against EAB.
Anyone considering use of Emamectin Benzoate should be aware that although ash trees are primarily pollinated by wind, rather than insects, the wind distributes ash pollen ubiquitously into other flowers. As a result, significant quantities of ash pollen are commonly present in bee hives, and pollen containing Emamectin Benzoate in any quantity can be acutely toxic to bees.
Walker Tree Care offers a third option for clients who want to protect their ash trees, are concerned about pollinators, but are also on a limited budget and can’t afford to inject their trees two years in-a-row, or whose ash trees are already infested with EAB, but the trees are not too far gone to save.
Clients who have been treating with TreeAzin who are entering a period of high pest pressure, and are not able to treat two years in a row may want to switch to Emamectin Benzoate for one or two treatments (2 or 4 years), until pest pressure begins to decline. This has the benefit of reducing the number if treatments from up to 4 down to 2 in a 5-year period.
Clients who live in a high pest pressure area and have never treated their trees, or whose trees are showing signs of EAB infestation may want to begin with a treatment of Emamectin Benzoate, and then switch to TreeAzin to maintain their trees without undue risk to pollinators in the long term.
I will repeat for emphasis, anyone considering use of Emamectin Benzoate should be aware that although ash trees are primarily pollinated by wind, rather than insects, the wind distributes ash pollen ubiquitously into other flowers. As a result, significant quantities of ash pollen are commonly present in bee hives, and pollen containing Emamectin Benzoate in any quantity can be acutely toxic to bees.
Walker Tree Care is a licensed pesticide applicator by the Colorado Department of Agriculture. For more information on EAB, please visit the CDA website. https://www.colorado.gov/agplants/emerald-ash-borer