Sooty Mold Fungus & Injectible Borer Treatment

May-June 2012

This sooty mold fungus is found exclusively on beech and it grows only on the honeydew excreted from populations of the beech blight aphid Grylloprociphilus imbricator. This aphid feeds in dense colonies on beech leaves and twigs and produces large amounts of honeydew. Ample amounts of honeydew drip down on twigs below, enabling the sooty mold fungus to grow to a considerable size. I have seen a lot of sooty molds in my travels but I’ve never seen anything quite like this one. I’m thrilled that Oliver was able to conclusively identify this mystery pest. I think that being wrong is a humbling experience that motivates us to do better next time. Plus, I get to rub this in the noses of some of the other scientists who didn’t know either. Oliver, thank-you, I owe you a beer at the next ISAO conference!

As for the second item I discussed in the last issue, chlorosis and weeping cankers on white pine, I have been submitting symptomatic bark-cambium samples to Lab Services, University of Guelph and others that might be able to detect pathogens at the leading edge of the cankers. It may be a bit of a pest complex but I am not seeing the signs of white pine blister rust on these trees. I’ll keep monitoring them and keep you in the loop.

Confidor Available to Help Manage Borers in Ontario
Though it’s been a long row to hoe, Bayer Environmental Science, together with OMAFRA and MOE, has met the PMRA requirements and Confidor 200 SL is now officially available as an injectable insecticide treatment for several species of borers. The list of pests on the Confidor label include:

  • Asian long horned beetle
  • Brown spruce long horned beetle 
  • Bronze birch borer 
  • Cottony ash psyllid 
  • Elm leafminer
  • European elm scale
  • Hemlock woolly adelgid
  • Locust leafminer
  • Woolly apple aphid

The active ingredient in Confidor is imidacloprid, a Class 9 pesticide. The product itself, Confidor 200 SL, is a Class 3 product. Only Class 11 products are allowed for cosmetic purposes under the Ontario Pesticide Ban. However, Confidor can be used under the arboriculture exemption if the conditions are met, i.e. a written opinion of a qualified tree care specialist. The opinion of a qualified tree care specialist must indicate that the use of a Class 9 pesticide is necessary to maintain the health of the tree(s) and the licensed exterminator must provide a written notice to the occupants of the residential area properties abutting the application area prior to use of the pesticide. If the treed area is 1 hectare or greater, Confidor can be used by a licensed forestry exterminator under the forestry exception. Confidor is being sold by Plant Products. 

Both TreeAzin and Confidor are registered to protect ash trees against emerald ash borer in Canada. Each product is used at different rates and the modes of action for the two active ingredients are different from each other. TreeAzin is used exclusively in Bioforest’s ecoject trunk injection system that many arborists are using. Confidor is sold as a solution and does not come with an injectable system. Confidor can therefore be used in any trunk injection system that allows the user to fill their own injection containers. Recently, Urban Forest Innovations has made Arborjet Tree Injection Systems available for use in Canada.  

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