Plant Phenology Indicators: GDD Base 10C: 150-200
1. Aesculus hippocastanum (horsechestnut, full bloom) 2. Cornus alternifolia (pagoda dogwood, early bloom) 3. Spiraea vanhouttei (bridal wreath spirea, full bloom)
4. Syringa vulgaris (common lilac, full-late bloom)
5. Prunus serotina (black cherry, early-mid bloom)
The Crop Protection Guide for Nursery and Landscape Plants (OMAFRA publication 840) contains the crop pest recommendations for nursery and landscape. Download it onto your phone or computer for easy reference.
Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape database to help ID your problem pests.
Crawlers of Oystershell Scale have hatched in container production and are starting to hatch in the field/landscape (adults shown above).
These crawlers are tiny and brown and very susceptible to insecticides including insecticidal soap and the summer rate of horticultural oil. This scale species can be found on several deciduous trees including lilac, ash, magnolia, maple, hackberry, willow etc.
Gypsy moth larvae are feeding on several species of trees (oak, linden, hackberry, beech, Colorado spruce). Look for holes chewed leaves and turn over inspect leaf undersides for dark, fuzzy larvae (15-20mm long). Gypsy moth larvae may also hide in bark crevices during the dayManagement of Gypsy moth larvae can be achieved using Bacillus thuringienesis (B.t., Dipel, Foray) and spinosad (Success) insecticide, with good coverage, especially in the first 2 weeks after larvae start to feed. Some keen homeowners can install a burlap skirt at the base of the tree to create a shady, protected area for larvae to hide during the day (this behaviour usually peaks near the end of May). Homeowners will need to inspect burlap skirts and underlying bark crevices daily (1-3 pm is best) and remove/destroy larvae.
Fall cankerworm (Alsophila pometaria) larvae can be found chewing interveinal leaf tissue, especially on the leaf undersides. Larvae are pale green (although you’ll often see darker races too) and blend in with foliage. They are about 12-20 mm long right now and they are really hungry. Monitor for larvae on several hosts such as Acer, Tilia, Quercus, Ulmus etc. A foliar application of the bio-insecticide Dipel (Bacillus thuringiensis, B.t.). can help to significantly reduce populations and subsequent injury.
Potato leafhopper ADULTS are feeding on woody nursery stock and laying their eggs on foliage in the NURSERY. Monitor for potato leafhopper on nursery crops such as Acer (platanoides, saccharum), Quercus and Ostrya. Adults will fly away quickly but once nymphs hatch, they will scuttle SIDEWAYS, rather quickly, across the leaf and to the other side (they don’t have wings). Susceptible crops are those that are flushing new leaves (leafhopper’s favourite food source). Older, hardened off foliage is not usually as susceptible. Leafhoppers (and aphids) suck plant sap from soft, expanding foliage and cause foliage and stems/petioles to wilt, turn brown/black (‘Hopper Burn”) and become stunted and malformed.
Older, hardened off foliage will become flecked from potato leafhopper feeding but younger foliage is more severely damaged. Monitor populations and treat where new foliage is emerging. Leafhoppers are also attracted to yellow sticky cards, for monitoring. Registered insecticides include acephate, acetamiprid, carbaryl, permethrin.
Where new foliage has not hardened off yet, monitor for needlecast and blight diseases on conifers in the area.
Diplodia tip blight on 2 and 3 needled pines and Rhizosphaera needlecast (above photo) and Stigmina on blue Colorado spruce are our most common needlecast diseases in Ontario. Diplodia tip blight appears as brown, stunted needles at the tips of branches. Rhizosphaera appears as brown-purplish needles from the previous year’s growth, symptomatic needles begin to drop in late spring. Stigmina appears on green and chlorotic needles, but doesn’t always lead to needle drop. To confirm it is Rhizosphaera, look at the undersides of the needles. Those little white dots (stomata) will turn black and the black spots will protrude during sporulation. New, soft growth is especially susceptible to foliar diseases, but infection may also take place later in the season. Where there is a history of damage, treat with registered fungicides (copper oxychloride, Banner Maxx, Daconil) as new foliage continues to emerge Apply fungicides prior to precipitation events (spore dispersal). Unfortunately, most of these blights and needlecasts can be found sporulating for much of the year.
Have white grubs (e.g. European chafer, June beetle) or Japanese Beetle phytosanitary restrictions been an issue at your nursery? Preventative applications of Intercept (imidacloprid) and Acelepryn (chlorantraniliprole) are registered for white grubs in nursery production and the application period will begin late June. Japanese beetle adults usually start to show up mid – late June in southern Ontario. Apply preventative soil drench applications for JB at the beginning of the adult flight period, usually when the Tilia cordata start to bloom you can monitor for them.
Monitor for nymphs of spruce spider mite on conifers with a history of mite damage (Abies, Picea, Thuja). Spruce spider mites appear as very tiny, brown mites with black backs. YOU WILL REQUIRE A HAND LANDS TO SEE THEM CLEARLY. Monitor lower branches, on the North and Easter side of the tree, this is where most of the feeding damage is done. Miticides are effective against nymphs and adults (Floramite, Kanemite, Vendex). They are a cool season mite and have been increasing in some areas, they love this kind of weather.
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