The black locust (Robinia pseudoacacia) are in full bloom as this is the phenology indicator species for the emergence of emerald ash borer adults.
Ash trees are fully leafed out now. Injectable insecticides may be used to protect ash trees from new infestations of Emerald Ash Borer (Agrilus planipennis). Trees must be actively transpiring in order to maximize insecticide uptake into the xylem (sapwood). Make applications when the pest has been detected in your area (or within 24 km) and trees still appear healthy. Registered injectable insecticide products include: AceCap 97, Ima-Jet and Tree-Azin. Check out the Management Strategy for Emerald Ash Borer and Bronze Birch Borer. The regulated areas for Emerald Ash Borer in Ontario and Quebec can be found here.
Asian Longhorned beetle has been detected in to Toronto-Mississauga area and injectable insecticides (Ima-jet) can be used to protect trees from this borer. Labelled host tree species include Elm, Maple, Birch, Willow, Box-elder, Horsechestnut, Buckeye, European Mountain-ash, Ash, Poplar, Albizia, London Plane, Hackberry and Sycamore.
European elm scale can be a problem on ornamental Camperdown elms (Ulmus glabra ‘Camperdownii’). Female scale are showy now with the white fringe around them. Look for them on the undersides of twigs and branch crotches. Female scales are just starting to lay eggs now. Injectable insecticides (Treeazin) can be used to help suppress the next generation of crawlers once they start to feed on twigs. Other options include scrubbing off females scales with a scouring pad before crawlers hatch (now). (I’ve done it and it has worked well) Or you can treat crawlers with sprays of insecticides in the coming weeks, once crawlers have emerged.
Birch Leafminer has been a problem on birch trees in the landscape. Injectable insecticides (Treeazin) can be used to help reduce the next generation of larvae that will be hatching soon.
Dutch elm disease (Ophiostoma ulmi) is a huge issue on elm trees in the landscape. Hopefully the wet weather will help our elms be able to fight off infections of this nasty systemic fungal disease. Look for leaves on individual branches to wilt, turn yellow and then fall off, leaving dead branches behind. Where trees are symptomless or show a small percent of canopy dieback, Arbotect 20-S can be used to help protect trees from future infections.