April Showers, Bring May Diseases

SugMapleFlowerSkyComp

Sugar maples in mid-bloom (J. Llewellyn)

Sugar maples are blooming all over southern Ontario, again! Did the hot, dry summer of 2016 have something to do with this?  The unusually warm February has accelerated plant development.  The (normally) distinct blooming time of several common ornamental plant phenology indicators are overlapping this year, making plant phenology models a little tricky to follow this spring.

Cool temperatures, cloud and rain has been pretty common across southern Ontario, slowing plant development.  We inched up a little in Growing Degree Days and Plant Phenology this week because of Thursday but its looking like the cool weather is going to stay with us for a while yet.  This weather keeps emerging leaves in a holding pattern, prolonging the period of time when they are most susceptible to diseases. The prolonged leaf wetness periods aid diseasess in successful infection and colonization of this tender foliage. Protect ornamentals with a history of disease, prior to precipitation events.

Plant Phenology indicators this week, north of 401, include:

  1. Acer platanoides (Norway maple, early bloom)
  2. Acer saccharum (sugar maple, many in full bloom)
  3. Acer rubrum (red maple, late bloom)
  4. Amelanchier spp. (service berry, mid bloom)
  5. Cornus mas (Cornelian cherry dogwood, full to late bloom)
  6. Forsythia (late bloom).  
  7. Magnolia x soulangiana (saucer magnolia, early bloom)
  8. Magnolia stellata (full to late bloom)
  9. Flower bud (not blooming yet): Syringa vulgaris (common lilac).

This puts us at about 55+ GDD (Base 10C) in areas such as the GTA and Hamilton.  Areas in the southwest region of the province will be more advanced (65+). Plant Phenology will find-tune timing when using BugFinder, the scouting app for pests of Nursery-Landscape plants (FREE download from the Apple App Store).

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.

Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape database to help ID your problem pests.

CONTAINER PRODUCTION NURSERIES-

Leaf spot on Cornus (T. Lohrer)

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. Leaf spots are often circular or angular with a bright purple border, making shrubs look unsightly by early summer, with possible early leaf drop.

PseudomonasSyringaBloomerang 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

<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 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.

<a href="/clm/species/cacopsylla_buxi"><em>Cacopsylla buxi</em></a> (Boxwood Pysllid) nymph on boxwood.

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.

DECIDUOUS WOODY AND HERBACEOUS PERENNIALS- Field & Landscape

 

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 open and leaves emerge. 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 of Prunus (University of Minnesota Extension)

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

FilbertBlightTorontoBotGarden

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).

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.

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) 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.

BoxLeafMinerDamageApril

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?

Crop2BoxLfMinerLeafLarvaApril

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.

 

img_2429 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 during dry soil conditions 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.

<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). 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/diaphnocoris_clorionis"><em>Diaphnocoris clorionis</em></a> (Honey Locust Plant Bug) nymph.

Honeylocust Plant bug NYMPHS (D. Cheung)

Where foliage starts to emerge on honeylocust, monitor for newly hatched nymphs of the honeylocust plant bug.  We had some pretty significant damage from this pest in 2016 so we are expecting moderate-high populations this year.  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 (video) 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 eggs (educatingcreatively.blogspot.com)

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).

EVERGREENS:

Balsam twig aphid stem mother on swollen bud. (Photo credit: Rayanne Lehman, Penn. Dept. of Ag., Bugwood.org)

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.

                                                          Tap twigs over a black surface to easily see teeny-tiny BTA stem mothers.  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.

<a href="/clm/species/pissodes_spp"><em>Pissodes sp.</em></a> (White Pine Weevil) adult. 

Overwintering white pine weevil adults are active and are laying eggs 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.

DCEastSprGallOWFem                                                    Cooley spruce gall adelgid and Eastern spruce gall adelgid overwintering females have already started laying their eggs and are no longer susceptible to insecticides. Use a pin to push away the woolly masses covering the female bodies to see the tiny brown eggs.

<a href="/clm/species/oligonychus_ununguis"><em>Oligonychus ununguis</em></a> (Spruce Spider Mite) eggs.                              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 Eastern 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.

JuniperTipBlightClose 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.

What’s That SOUND?

Related image                                              There is a toad species that started calling on the warmer nights last week. This is the American toad (above, fishpondinfo.com).  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 🙂

 

 

 

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This entry was posted in Arboriculture, Diseases, IPM, Nursery Production, Weekly Nursery Landscape Report and tagged , , , , , , . Bookmark the permalink.

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