Those Precocious Blooms of April!

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      Norway maple (Acer platanoides and its cultivars) are just starting to bloom in the GTA, making this one of the earliest blooms for trees since 2012!

 Plant Phenology indicators this week are a little overlapping. North of 401 and GTA include: Acer saccharum (sugar maple, full to late bloom); Cornus mas (Cornelian cherry dogwood, full to late bloom); Forsythia (full to late bloom); Salix caprea (pussy willow, early bloom); Acer platanoides (Norway maple, early bloom), Magnolia stellata (star magnolia, full bloom) Magnolia x soulangiana (early bloom).  Southwestern Ontario is likely a little further along, many areas between 40-75 GDD.  The crazy amount of heat we had over the last few weeks has hastened the development of many plants, causing some unusual overlap in the bloom period for different species.

If you are referring to the Phenology and Monitoring tables in OMAFRA publication 841, Guide to Nursery and Landscape Plant Production & IPM, look at the Tables starting with 2-3 on pg. 39.

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Check out BugFinder, the scouting app for pests of Nursery-Landscape plants!  Its a FREE download from the Apple App Store. and from Google Play. Much of the info found in these blog articles can be found in greater detail in BugFinder.

PLEASE NOTE: The Following Pesticide Recommendations are meant for Exception Uses (e.g. agriculture-nursery production or trees in the landscape) under the Cosmetic Pesticide Ban unless the active ingredient is listed under the Allowable List pesticides in Ontario Regulation 63/09.

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.

The new 2021 edition of publication 840 will be available SOON!

DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:

Once ash trees have leafed out, injectable insecticides may be used to protect the trees from new infestations of Emerald Ash Borer (Agrilus planipennis). Trees must be actively transpiring in order to maximize insecticide uptake into the cambium. Registered injectable insecticide products include: AceCap 97, IMA-jet and Tree-Azin.  The regulated areas for EAB outlines restrictions on the movement of all ash species (Fraxinus sp.) materials and all species of firewood from these regulated areas of Ontario and Quebec.

If you are bringing in SOD (Sudden Oak Death, Phytophthora ramorum) host nursery stock from high risk areas, you will want to monitor for SOD symptoms. Camellia, Rhododendron, Viburnum, Pieris, Kalmia and Syringa are considered to be high risk host genera, as they are most common genera found positive for SOD in retail and wholesale nurseries. Fungicides registered for SOD in nurseries include: Acrobat 50 WP, Chipco Aliette WG and Subdue Maxx.  For a complete list of SOD regulated hosts, check out: http://www.inspection.gc.ca/english/plaveg/protect/dir/sodspe.shtml

<a href="/clm/species/otiorhynchus_sulcatus"><em>Otiorhynchus sulcatus</em></a> (Black Vine Weevil) larva.                      In production nurseries where black vine weevil larvae are a problem in container crops (e.g. perennials, evergreens), monitor containers for larvae and pupae. Once soils reach at least a consistent 10oC, treat with beneficial nematodes Heterohabditis bacteriophora (H.b.).  This should result in a significant reduction in populations in under two weeks.  Order your nematodes in advance.  Since Heterohabditis nematodes require moist, warm soil, we find that they work best in container production.

EuropeanChaferLarvaSoilECLarvaPinus           Take a look at the roots of poor looking evergreens (Thuja, Picea, Pinus) and field grown ornamentals and look for populations of European chafer, May/June Beetle larvae and other white grub species in the soil. Sandy soils are especially hospitable to white grub species.  Preventative applications of Intercept (imidacloprid) and Acelepryn (chlorantraniliprole) are registered for white grubs (nursery production) and the application period is in June and July (during the adult flight period). (Beneficial nematode applications are not recommended this time of year and are much more effective when applied to early instar larvae, mid-August.)

IronWoodAnthracnose Where Ironwood trees (Ostrya virginiana) were infested with anthracnose spots last year, you may consider an application of broad spectrum fungicide (e.g. copper) as buds start to swell. The usual symptoms caused by this fungus, Apiosporopsis carpinea, are irregular necrotic spots ranging in size from pinpoints to 5-6 mm in diameter. They will increase in number and coalesce during the season and will cause marginal and apical browning, curling and leaf cast.

Black knot is easy to see on Prunus sp. at this time. Monitor gardens and adjacent wild areas for Prunus shrubs and trees for large black growths on previous years twigs. If you have the time to prune, prune the cankers out, back quite close to the main stem BEFORE LEAVES EMERGE. Destroy all pruned twigs. Pruning too shallow retains the undetectable, developing canker on the tree and does nothing to limit the disease. Fungicides may give some suppression when sprayed at green tip, pre-bloom and blossom time. Fungicides include Daconil and Maestro. Fungicides need to be applied ahead of precipitation events during bloom and shoot emergence In the nursery/orchard, Daconil has been shown to be the most effective fungicide. (Fruit-bearing mature Prunus: Daconil cannot be applied after shuck split or fruit will be injured). For more information: http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2003/03hrt03a4.htm

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Monitor ornamental Corylus sp. for signs of Filbert Blight. This is a fungal disease that causes rows of small, black, crescent-shaped cankers along dead stems. Remove cankered shoots, 20-30 cm behind visible cankers, when plants are dormant. Disinfect pruning shears between each cut. Do not prune once new growth starts emerging. Corylus avellena ‘Contorta’ is particularly susceptible. Spray fungicides to protect new growth, starting at bud swell to bud break. Registered fungicides for this disease include: Copper oxychloride 50, Copper Spray and Flint (Compass).  Always spray pruners and cut surfaces with rubbing alcohol.

Applications of horticultural oil can still be applied this week where no green foliage or delicate flower tissue has emerged (where necrosis could be an issue). Timing of dormant rate horticultural oil applications are critical since freezing temperatures, mixing with sulphur and applying at the dormant-rate on actively growing tissue may result in injury. Read more about dormant oil bly clicking on “Dormant Horticultural Oil App’s This Week“.

(Keep in mind that dormant horticultural oil applications are not effective against Euonymus scale, Oystershell scale and pine needle scale and will have only very limited efficacy against Fletcher scale and Lecanium scale.)

<a href="/clm/species/oligonychus_aceris"><em>Oligonychus aceris</em></a> (Maple Spider Mite) eggs on maple.  Remember the maple spider mite (Oligonychus aceris) injury you saw on the silver-red maple hybrids last year? The tiny, red, overwintering eggs of those maple spider mites can be found on the leaf scar, just below the bud for this years growth, on last year’s twigs. The mite eggs are tiny flat, red spheres and are just barely visible; you will need a hand lens to see them. Where populations caused damage last year, applications of horticultural oil prior to leaf emergence should help smother eggs and reduce the population.

img_2429 Birch trees with a history of bronze birch borer infestation should be pruned by now. Symptoms appear as branch tip death, branch death and death of the leader and progresses quite quickly. Destroy pruned material to prevent emergence of beetles. Natural resistance to this pest can be enhanced through activities that improve plant health, such as light fertilizing (May, October), irrigating and removing any weeds and grasses that provide competition for the tree. Betula pendula (European birch) is most susceptible to this pest and should be avoided in areas of known BBB infestation. Betula nigra (river birch) and its selections have been shown to be quite tolerant to BBB attack.

<a href="/clm/species/dasyneura_gleditschiae"><em>Dasyneura gleditschiae</em></a> (Honey Locust Pod Gall Midge) galls.<a href="/clm/species/dasyneura_gleditschiae"><em>Dasyneura gleditschiae</em></a> (Honey Locust Pod Gall Midge) adult.

Where honeylocust podgall midge was a problem in the past, monitor trees for overwintered adult midges soon. These adults will be emerging as the buds start to swell. Adults will be laying eggs on buds in early spring (reddish eggs on buds and new leaves). Recent research in Oregon suggests that delayed dormant oil applications targeting the first couple of egg clutches can help reduce the incidence of pod gall midge. This involves applications of product early in the season, starting before foliar emergence.

<a href="/clm/species/pyrrhalta_viburnicola"><em>Pyrrhalta viburnicola</em></a> (Viburnum Leaf Beetle) damage on viburnum.

Viburnum leaf beetle egg masses can still be pruned out and destroyed at this time (where leaves haven’t begun to emerge yet), to avoid destructive populations this spring. Look for raised bumps on the undersides of 1 and 2-year-old twigs. The bumpy caps can be picked off to reveal the yellow eggs underneath. Monitor these eggs as they will hatching into larvae as foliage emerges. The larvae are vulnerable to chemical control only during the first 7-10 days after hatch. Larvae feed on the interveinal tissue from the undersides of the leaves, keep that in mind if you are doing insecticidal applications (Success, Actara, horticultural oil).

Spring peepers and Wood Frogs are singing in many areas of Southern Ontario and have been for a couple of weeks now.  The wood frogs are still calling but the cooler weather this week has quieted the peepers down a bit, but they’ll be back out with the sun and warmer temps coming tomorrow. Spring frog calls are one of my most favorite wildlife calls and first real confirmations of spring!

About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
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