This cooler weather has been a nice break, slowing down plant development and reducing heat and desiccation stress on newly planted or harvested nursery stock. We inched up a little in Growing Degree Days and Plant Phenology this week.
Plant Phenology indicators this week, north of 401, include:
- Acer saccharinum (silver maple, many in late to finishing bloom);
- Acer rubrum (red maple, mid to latebloom);
- Cornus mas (Cornelian cherry dogwood, early to full bloom, UPPER LEFT PHOTO),
- Forsythia (full to late bloom, UPPER RIGHT PHOTO).
- Salix caprea (pussy willow, full bloom);
- Flower bud (not blooming yet): Acer platanoides (Norway maple), Amelanchier laevis (serviceberry), Syringa vulgaris (common lilac).
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. This puts us at about 30-55 GDD Base 10C in areas south of Hwy 9. Areas in the southwest corner of the province will be more advanced.
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. The new 2016 version of Publication 840 will be available online in the next few weeks. The pest recommendations can also be found on our online, searchable database: www.nurserytracker.com. Check out NurseryTracker on your phone or tablet!!!
Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape database to help ID your problem pests.
CONTAINER PRODUCTION NURSERIES-
Where dogwood (Cornus spp.) has had issues with fungal leafspots (e.g. Septoria) in the past, protect emerging foliage with fungicides before precipitation or irrigation events as the Amelanchier sp. and Cercis canadensis are blooming. Leafspots are often circular or angular with a bright purple border, making shrubs look unsightly by early summer.
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 10-12oC and treat with Heterohabditis bacteriophora (H.b.) or Met52. 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. Met52 can also be applied preventatively at potting.
Monitor boxwood for bud swell and hatching of overwintering boxwood psyllid nymphs as the Cercis canadensis begins to bloom, Acer platanoides are in late bloom and Magnolia x soulangeana are dropping petals. Eggs are very tiny, spindle-shaped and buried within the bud scales of this year’s growth with just the tip protruding out. Boxwood psyllid eggs hatch just as buds are starting to break and expose tender new shoots. Psyllid nymphs are yellow-green and blend in very well with new growth of boxwood. Their feeding causes cupping and distortion of new growth. Spray with insecticidal soap or contact insecticides at first sign of bud break and repeat 2-3 times to suppress populations of hatching psyllids. Systemic insecticides, such as dimethoate, are registered for use in commercial nurseries.
In container nurseries, where Pseudomonas blight on lilac (and other deciduous shrubs) was a problem last season, you may want to consider an application of copper as they bud out. Research also indicates that the copper becomes more effective if combined with Dithane. The bacteria overwinter next to the buds and can infect leaf tissue once bud caps split open. Again, infection and spread of this bacterial disease can be reduced where temperatures and humidity levels are moderated (i.e. ventilation under poly) and new foliage is more gradually hardened off to outdoor conditions.
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
Where nursery stock continues to be maintained in a polyhouse, caution should be taken when applying pest control sprays. Temperatures in the polyhouse can spike on clear sunny days, causing the chemical to injure foliage. Ventilation holes should be cut to keep high temperatures and high humidity at bay. High humidity has been linked to distortion and stunting of new growth on vines and shrubs and should be addressed where these symptoms have been observed.
DECIDUOUS WOODY AND HERBACEOUS PERENNIALS- Field & Landscape
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, Confidor 200 SL, 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.
The Asian Long Horned Beetle was detected in the vicinity of Pearson International Airport in Toronto/Mississauga and efforts are continuing to eradicate this beetle from the area. The Asian Long-horned Beetle Infested Place Order is being enforced in the area encompassing: all parts of the City of Toronto and City of Mississauga, in the Province of Ontario, located within the area commencing at the point of intersection between Dixie Road (formerly Hwy. 4) and Derry Road (formerly Hwy. 5) and proceeding northeastward along the south side of Derry Road to Bramalea Road. This means that tree materials, including nursery stock, trees, logs, lumber, wood, and wood and bark chips from tree species that are susceptible to the Asian Long-horned Beetle, may not move out of, or through, this area.
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) 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.
Boxwoods in the landscape not looking so good coming out of the winter? Are you seeing a lot of yellow leaves? Can you see any yellow-green spots?
Carefully break open the leaf with your knife or finger nail, look for tiny yellow larvae inside. These are boxwood leafminer larvae and they will be pupating soon. The tiny orange midge adults will be emerging out of these leaves when the new growth emerges. Adult midges will be laying their eggs on newly emerged leaves and those eggs will hatch into the next generation of leaf miners. Treating new foliage with insecticides just prior to or at the beginning of leaf emergence can help reduce successful egg hatch and leafminer establishment. You can also prune out new foliage in August and the clippings will desiccate, making it impossible for the leafminer to complete its lifecycle.
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 suppressions 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).
Birches 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 is most susceptible to this pest and should be avoided in areas of known BBB infestation. Betula nigra 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). 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.
Where foliage is starting to emerge on honeylocust, monitor for newly hatched nymphs of the honeylocust plant bug. You can find them by shaking branches over a light coloured surface and examining it for fallen nymphs. By controlling the first generation of nymphs, you can really reduce the damage from this pest.
Eastern tent caterpillars will be hatching at budbreak and these tiny, black fuzzy larvae will start feeding and making webby tents in branch crotches. Manually remove and destroy the egg masses of Eastern tent caterpillar where they are still dormant. The egg masses appear as swollen, shiny grey bands around small twigs of cherry, crabapples and hawthorns. They actually glisten in the sunlight. The larvae can cause severe defoliation in May, where populations are high. Young larvae hide in webby tents during the day, remove and destroy tents during daylight hours in the first week or two after their appearance. Where larvae start to feed, try an application of the biological insecticide B.t (Dipel, Foray) on the foliage during the evening hours. Larvae will turn black and die approximately 3-5 days after eating the B.t. residue on the foliage.
Gypsy moth egg masses can be scraped off and destroyed at this time. The egg masses appear as raised, buff coloured fuzz on tree trunks, fence posts, buildings and other sheltered locations. When larvae begin to emerge (when trilliums are in full bloom), some control can be achieved using Bacillus thuringienesis (Dipel, Foray) and spinosad (Success) insecticide in the first 2 weeks after egg hatch. 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. Sticky bands around trunks during the June/July flight period will help prevent females from laying eggs above sticky bands and will attract males to the sticky surface.
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 will be hatching in the coming weeks and developing into stem mothers (nymphs). The tiny, bluish grey aphid stem mothers can be found on terminal buds as they break. Apply Diazinon, 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.
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, on the undersides of twigs. They are just barely visible with the naked eye. Galls do not usually have much effect on plant growth but appear unsightly in summer when they turn brown. Where populations are high, the adelgids are susceptible to chemical control (or horticultural oil applications when dormant) BEFORE buds start to swell and while nymphs are still blue-ish. Target pesticide applications to the undersides of shoot tips. Use wettable powder formulations on blue spruce to prevent foliar discolouration. 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 in the next few weeks, where temperatures permit and plant species are not sensitive. Miticides 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 10-12oC. 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.
The spring peepers are still calling in many areas with the cooler weather. These tiny frogs pack a huge song in their little reptilian bodies, and for good reason. They only have one shot at it each year.
Wood frogs should be finishing up in most areas, they have a really short mating season. They will come down to temporary wet areas, like roadside ditches, in early spring to mate with females.
Another early spring species, the Northern Leopard Frog, is also calling in wet, wooded areas. These guys sound like “snoring” and can be heard day and night during peak breeding. You probably recognize this species by site and they are commonly encountered in the summer months in wet ponds and shallow lakes.
And lastly, there is a toad species that will be calling once the nights are a little warmer. This is the American toad. The mating call is a one-tone trill that some nature lovers can find….a little annoying. They too are found in temporary flooded wooded areas and are common in backyards. I bet you’ve heard them in the evening, you just didn’t know it 🙂