Lots of early Plant Phenology indicators are blooming this week! That puts us somewhere around 15-25 GDD’s Base 10C in the GTA. A little more in the southwest (London and west).
Plant Phenology indicators this week are a little overlapping. North of 401 and GTA include: Acer saccharinum (silver maple, mid bloom); Acer rubrum (red maple, 10-40% bloom); Cornus mas (Cornelian cherry dogwood, early to mid bloom); Salix caprea (pussy willow, early bloom); Acer platanoides (Norway maple, not blooming yet), Magnolia stellata (star magnolia, flower bud). Niagara and southwestern Ontario are further along, some areas between 25-50 GDD. 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.
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 Class 11 pesticides in Ontario Regulation 63/09, effective April 22, 2009.
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 pest recommendations can also be found on our online, searchable database: www.nurserytracker.com. Check out NurseryTracker on your phone or tablet.
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
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 and 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.
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.)
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
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).
Applications of horticultural oil can still be applied this week where no green foliage or delicate flower tissue has emerged. 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. Apply hort oil on dormant plants, on clear mornings to facilitate rapid drying. The oil provides a barrier that restricts both respiration and movement of overwintering insects. It is quite effective for the management of overwintering scale Nymphs and mite eggs (including spruce spider mite, European red mite, maple spider mite on silver/red hybrids). Keep in mind that most of these insects overwinter on the undersides of leaves and twigs. Since the oil droplets come out of solution so easily, frequent agitation is VERY important during application. Dormant applications of horticultural oil are very effective against Magnolia scale and San Jose scale (on fruit trees).
(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.)
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.
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.
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.
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).
Monitor for overwintering Balsam twig aphid eggs on terminal buds on fir, white spruce, Colorado spruce and juniper, they are susceptible to dormant oil applications. Eggs are just starting to hatch (nymphs, a.k.a. “stem mothers”) west of London, still dormant north of hwy 401. The tiny, bluish grey aphid stem mothers can be found on terminal buds as they break. Apply Malathion and Tristar on warm days (55 to 78 GDD Base 10oC OR before bud caps loosen off) to target these stem mothers and prevent the damaging generation that follows. Photos:
Overwintering white pine weevil adults are active and are mating on last year’s leader of pine and spruce, when the Forsythia starts to bloom. Monitor for small black/brown snout beetles around the foliage and in the duff layer below the canopy. An application of insecticide on last year’s leader may help reduce successful egg-laying and damage to this year’s leader.
Cooley spruce gall adelgid and Eastern spruce gall adelgid overwintering females appear as tiny (you’ll need a hand lens to see them), grey/blue fuzzy spots at the base of buds, or on twigs near the need base. They are just barely visible with the naked eye. Once they are covered in a white, woolly material, they have begun egg-laying and are no longer susceptible to pesticides. Heavy populations of spruce gall adelgid are often a sign of some other underlying cause of stress or root problem in the tree. Where infestations are small, you can remove and destroy green galls in June to reduce populations.
Monitor for eggs of spruce spider mite on conifers with a history of mite damage (Abies, Picea, Thuja). Spruce spider mite eggs appear as very tiny, round, reddish-brown spheres that adhere to the UNDERSIDES of twigs and foliage this time of year. 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. These eggs are susceptible to dormant hort oil applications, where temperatures permit and plant species are dormant are not sensitive. Miticides (Floramite, Kanemite, Vendex) will be effective once eggs hatch to nymphs, usually around bud break and early foliar emergence.
Pine shoot beetle adults have emerged. The tiny beetles take flight after 2-3 days where temperatures reach 10-12 Celsius. Adults lay eggs underneath the bark of stressed or dead pine trees and stumps. Those larvae will develop later in April and May. Remove brood material (i.e. trap (sentinel) logs, snags, dead/dying trees) before new progeny adults emerge (210 GDD, Base 10C) to comply with the CFIA. All brood material must be burned, chipped (less than 2cm diameter) or buried (30 cm deep) to comply with CFIA standards.
Brown shoots on juniper may be a symptom of juniper tip blight (Kabatina blight). A small grey band or pinched grey canker can be found at the base of the infected shoot, this is where the spores come from. Where plants are still dormant, PRUNE OUT DEAD SHOOTS during DRY conditions (and remove shoots) to reduce disease spread. Disinfect pruning shears between each cut (e.g. rubbing alcohol, other sterilants) to reduce disease spread. Pruning is not suggested once new growth appears, as it will help spread this disease. Where cankers are found, copper and Dithane are registered to protect emerging new growth this spring and summer.
Spring peepers are starting to sing in many areas, especially south of the 401. This is one of my most favorite wildlife calls and first real confirmations of spring. It’s one little frog with one huge voice. Happy Monday 🙂