June 7, 2013 Nursery-Landscape Report

You have reached Jen Llewellyn for the eighth edition of the 2013 OMAF and MRA Nursery and Landscape Report, updated on Friday, June 7th.

Environment Canada is calling for cloudy weather with the chance of shower for Friday and Saturday and temperatures ranging from 18-22oC in many areas. Sunday will be warmer with more sunny skies, highs in the range of 21-24oC. If your suffering from seasonal allergies a little more than usual this year, it’s because so many plants are flowering (pollen) simultaneously instead of consecutively. Spring budbreak was so delayed this year that so many plants were poised to flower and the early heat accelerated plant development.

Would you say this is a bad year for plant pests? Every other week it has been hot and humid with thunderstorms….which is good for diseases. Every opposite week from that it has been cool which slows down hardening off of leaves….which is good for insect pests, especially sucking insect pests, like aphids. I am seeing a fair amount of disease (fungal, bacterial, virus) and insect pests in the landscape this year.

Plant Phenology indicators this week.
A) North of 401 (150-200 GDD Base 10oC): Aesculus hippocastanum (late bloom, Lonicera korolkowii (full bloom), Spiraea vanhouttei (full to late bloom), Cornus alternifolia (full bloom), Robinia pseudoacacia (full to late bloom), Pinus mugo (candling), Acer saccharinum (dropping seed), Viburnum opulus (mid bloom)
B) Niagara: Aesculus hippocastanum (late bloom, Lonicera korolkowii (late bloom), Spiraea vanhouttei (full-late bloom), Cornus alternifolia (early-mid bloom), Robinia pseudoacacia (late bloom), Pinus mugo (candling), Acer saccharinum (dropping seed), Viburnum opulus (late bloom)
C) London area: if you would like to report plant phenology events, please contact me.
D) Leamington-Windsor: if you would like to report plant phenology events, please contact me.

If you are referring to the Monitoring tables in the 2009 edition of publication 383, Nursery and Landscape Plant Production and IPM, look at Tables starting on pg. 64.

PLEASE NOTE: The Following Pesticide Recommendations are meant for Exception Uses (e.g. agriculture) under the Cosmetic Pesticide Ban unless the active ingredient is listed under Class 11 pesticides in Ontario Regulation 63/09, effective April 22, 2009.

pub840coverjlThe 2013 Crop Protection Guide for Nursery and Landscape Plants (previously 383, now publication 840) can now be found at: http://www.omafra.gov.on.ca/english/crops/pub840/p840order.htm
This contains the crop pest recommendations for nursery and landscape plants that was previously found in publication 383. Publication 840 is a .pdf file, accessible online and on cd.

Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape database to help ID your problem pests. Check out http://www.dkbdigitaldesigns.com/clm

Injectable insecticides may be used to protect ash 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 and Tree-Azin. Check out the Management Strategy for Emerald Ash Borer and Bronze Birch Borer at: http://www.omafra.gov.on.ca/english/crops/insects/eab-bbb-manage.htm. Emerald ash borer adults start to emerge when the black locust (Robinia pseudoacacia) are blooming.

The regulated areas for Emerald Ash Borer can be found at:
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.


In PRODUCTION NURSERIES where black vine weevil larvae are a problem in container crops (e.g. perennials, evergreens), treat with beneficial nematodes, Heterohabditis bacteriophora (H.b.). This should result in a significant reduction in populations within two weeks. Since Heterohabditis nematodes require moist, warm soil, we find that they do not work well in the landscape/field unless ample, supplemental irrigation can be provided for the 10 days following application. In container production, Met 52 can also be used prevenatively, at the time of potting, to help control all stages of black vine weevil. In the LANDSCAPE and GARDEN, check for overwintered LARVAE of black vine weevil on Rhododendron, Taxus, Thuja, Euonymus etc. in the garden and treat with nematodes when soil temperatures warm up.

Take a look at the roots of poor looking turf and field grown ornamentals and look for populations of European chafer and other white grub species in the soil. 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). To help qualify for the Japanese beetle certification program, an application of Intercept on container stock should be some time between mid-June to July. The cut-off period for Intercept applications to comply with the JB Certification program this year may be as early as July 31st. Beneficial nematode applications for white grubs (e.g. European chafer) are not effective at this time. Try timing nematode applications for late August/early September to catch early instar larvae.


Dutch Trig is registered for Dutch Elm Disease on Ulmus americana species in Canada. This is a new registration (fall, 2009) that contains a biological organism that induces an immune response to help the tree fight off DED infections. Arbotect-20-S (thiabendazole) is the registered injectable fungicide treatment. Injections of these fungicides should be made on sunny days during leaf emergence to maximize uptake.

fireblightmaluswhipWhere Malus and Pyrus and Sorbus (mountain ash) are blooming and beginning to leaf out and it is WARM and WET, applications of bactericidal products (Copper, Kasumin (new), BlossomProtect (bio)) can help reduce the incidence of Fire blight infections during WARM, WET weather this spring. The weather this week is perfect for the spread and infection of Fireblight. Fireblight infection causes dead shoots on Malus and Pyrus, sometimes killing young nursery stock.

We have seen more powdery mildew on deciduous flowering shrubs (Amelanchier) and herbaceous perennials. Monitor for white, powdery residue on the tops and bottoms of leaves. Protect new foliage with fungicide applications (e.g. Switch, Milstop, Regalia (bio)) where the history of disease pressure is moderate to high.

dsc_0072Our nursery scout has seen a lot of powdery mildew-like symptoms on leaf surfaces (e.g. Amelanchier) this week in nurseries, but each time it turned out to be the calcium/magnesium residue of dried water droplets from irrigation. When viewed under a dissecting microscope or hand lens, powdery mildew looks woolly with thread-like strings. Dried residue from hard water looks like tiny, white crystals on the surface.

Peach tree borer (Synanthedon exitosa) adults will be flying in the next few weeks. Look for cankered regions and chewed bark/wood in the lower stems of Prunus (Prunus x cistena) as a sign of larval damage. The clearwing moths that emerge resemble wasps. Adults are very much attracted to sticky wing traps that are baited with peach tree borer pheromones. Place pheromone traps out in early-mid June (approximately 390 GDD Base 10oC, ‘Red Prince’ Weigela in full bloom) and monitor for peak flight of adults. You can expect peak egg hatch around 10-14 days later, if you are thinking of treating newly-hatched larvae. The same ‘clearwing moth’ pheromones and traps can be used to monitor for Viburnum borer. Viburnum borer chews the stem (at and below the soil line) and causes significant injury to container grown Viburnum. Viburnum borer will be starting to emerge in container production at this time. To purchase traps, try ordering from IPM suppliers such as http://www.greatlakesipm.com and http://www.naturalinsectcontrol.com. Some growers are trying soil drench applications of beneficial nematodes (Steinernema carpocapsae) after peak adult flight, as a biological way to suppress hatching larvae.

Birches with a history of bronze birch borer infestation should be pruned by now. Adult beetles are actively laying eggs. Symptoms of larval boring damage 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. Confidor injectable insecticide is labelled for bronze birch borer.

ADULT Potato leafhoppers have arrived in southern Ontario! Monitor for leafhoppers (such as potato leafhopper) on nursery crops such as Caragana, and Acer (platanoides, saccharum). Our nursery scout found them on Acer platanoides, Caragana and Celtis this week. Leafhoppers adults are winged, are very mobile, tiny, pale yellow-green jumping insects that are easily disturbed when you approach infested foliage. It almost looks as though they are being flicked off of the foliage. Adult potato leafhoppers blow in from the south and will feed and lay their eggs on newly expanding leaf tissue. The soft, succulent growth we have this year is especially susceptible. Leafhopper nymphs will be hatching soon and appear as tiny, flightless, yellow-green insects that move sideways, very rapidly across the leaf. Leafhoppers (and aphids) suck plant sap from expanding foliage and cause foliage to wilt, become off-coloured, flecked and stunted. Potato leafhoppers are especially damaging because they cause foliage to become stunted and deformed, with brown-black margins (“hopper burn”). Leafhopper injury also appears as bronzing or stippling on more mature leaves. Monitor populations and treat the 1st generation NYMPHS with insecticides before damage becomes economically threatening. Leafhoppers are also attracted to yellow sticky cards, for monitoring. Registered insecticides include Tristar and Sevin XLR. http://dkbdigitaldesigns.com/clm/species/empoasca_fabae

Aphids are quite numerous on herbaceous and woody ornamentals this spring! They do well in cool weather because leaves stay soft and easy to feed on. Green peach aphid is one of the most common species and melon aphid and foxglove aphid are also quite common. This year we are seeing large colonies of black bean aphid (Aphis fabae) on deciduous flowering shrubs and Euonymus. Aphids are sucking insects that cause stunting, malformation and coat plants in honeydew. They also attract ants. Various insecticides are registered to manage aphids in outdoor production nurseries including Endeavor, Tristar and Trounce. In greenhouses insecticides include Endeavor, Intercept and Enstar EW. Where populations aren’t immediately economically damaging, biological control (e.g. Aphidius, Aphidoletes) may provide excellent management when introduced on a regular basis. Biocontrol suppliers include Koppert, Plant Products and Canadian Hydrogardens.

Gypsy moth larvae (3rd and later instars) are going to be moving into their heaviest feeding period in the next couple of weeks. Larvae can be found on various deciduous trees and evergreens (Colorado spruce). Some larval management can be achieved using spinosad (Success) insecticide, Dipel, Foray etc. (B.t.,Bacillus thuringiensis). 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 larvae are feeding on the underside of Viburnum leaves. Look for tiny yellow larvae with black markings. 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). They are difficult to control with pest control products after they have been around for 2 weeks.

Oystershell scale crawlers are starting to hatch. Look for very tiny (2-3 mm), whitish-grey, oyster-shell shaped hard scale insects stuck on twigs and branches of deciduous trees and shrubs such as ash, birch, bittersweet, hackberry, redbud, beech and dogwood. Crawlers (light tan) are sensitive to insecticidal soap, horticultural oil, malathion and other insecticides (Viburnum opulus blooming, Aesculus hippocastanum late bloom). Two-three applications of insecticides may be necessary since crawlers hatch over 1-3 week period.
Two-spotted spider mites (TSSM) has shown up on Viburnum and Spiraea in container production in the past and has been reported on dogwood. Use your hand lens to see tiny, clear bodied mites with dark regions (may be faint black) on their backs. These mites are small but the damage is significant so catch them early. Miticides registered for this mite in the greenhouse include: DynoMite, Vendex, Kanemite, Floramite, Avid. Apollo is registered in outdoor nursery crops to knock down the egg stage and newly hatched nymphs later in the season. In the greenhouse, biocontrol agents should be brought in to coincide with the first sign of TSSM. Phytoseiulus persimilis is a predatory mite that feeds on TSSM when temperatures are below 26oC and it is a good choice when TSSM populations are low-moderate. Amblyseius californicus is a predatory mite that can be brought in ahead of TSSM appearance (because it can find other sources of food).

Where new foliage is emerging on conifers, monitor for needlecast and blight diseases in the area. Diplodia tip blight on 2 and 3 needled pines and Rhizosphaera needlecast 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 (we don’t know). Where there is a history of damage, treat with registered fungicides (copper oxychloride, Banner Maxx, Daconil) as buds start to open and protect new foliage. Apply fungicides prior to precipitation events (spore dispersal). Unfortunately, most of these blights and needlecasts can be found sporulating for much of the year.

The first generation of Euonymus scale crawlers are hatching in container production and will be in the field and landscape very soon. Euonymus scale look like tiny white flecks (males) and tiny brown sea shells (females) along twigs and the undersides of leaves. Look for bright, orange crawlers around populations of adults and on the undersides of leaves and twigs. Where insecticide applications are warranted, multiple applications may be required to get good knockdown since crawler emergence is staggered over a few weeks. Try insecticidal soap and the summer rate of horticultural oil.

Look for terminal shoots on pine and spruce for signs of browning, wilting and needle drop, it could be boring larvae from white pine weevil. Where appropriate, slice into bark and look for tiny, fat, white, legless grubs feeding in the cambium. Insecticide control is too late at this point, prune out and destroy all symptomatic terminals and train a new leader.

Larvae of European pine sawfly are feeding in clusters on last year’s (and older) needles and our nursery scout is finding them in many places. Larvae are greenish-yellow with dark head. They rear their bodies up in unison when alarmed. They can often be found on the top half of the tree, on the NE side. There are several insecticides registered for this pest. A low toxic pesticide choice is Success or Dragnet. Closely examine twigs of Pinus sylvestris, Pinus mugo, Pinus nigra.

Taxus or Fletcher Scale adults have laid their eggs on foliage and twigs of Taxus and Thuja. Pick tiny, dark, bulbous adult female scale off to reveal white eggs underneath (about the size of grains of salt). These eggs will be hatching over the next few weeks. Two-three applications of insecticide will be needed to reduce crawler populations and reduce further injury. Insecticidal soap and several contact insecticides are registered for Fletcher scale crawlers.
Taxus mealybug nymphs will be showing up. Adult mealybugs are bright white (3-5 mm), waxy looking flat insects that barely move. They can be found on twigs of older Taxus in field production in hedges. They produce honeydew therefore, black sooty mould is apparent on infested plants. Where populations are high, nymphs are sensitive to applications of insecticidal soap, horticultural oil, Trounce, Sevin and many others.

Cedar leaf miner larvae are pupating and tiny, grey-white adult moths are emerging. Tear along the margin of green and brown tissue and check for the presence of hollowed out tissue to confirm it is leafminer. We have seen quite a bit of CLM in field grown Thuja on sandy soils this spring. Adulticides (malathion) are registered for the moth life stage in nursery production.

Pine false webworm larvae will be found on white pine When eggs hatch, larvae snip off foliage and make webby nests near the trunk. The larvae clip off more needles and pull them into the webby nest where they feed on them. The larvae feed mainly on older growth and will only eat the current year’s growth when all else has been consumed. The new nests can be dislodged with a strong stream of water.

Cooley spruce gall adelgid and eastern spruce gall adelgid will be forming galls on new twigs of spruce at this time. 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) when buds start to swell. Target pesticide applications to the undersides of shoot tips. Use wettable powder formulations on blue spruce to prevent foliar discolouration. Heavy populations of spruce gall adelgid are often a sign of some other underlying cause of stress or root problem in the tree.

Monitor for nymphs and adults of spruce spider mite on conifers with a history of mite damage. Spruce spider mite nymphs and adults are brown with black backs and found on new foliage this time of year. Miticides registered for SSM include Floramite and Kanemite. Miticides may be required where pest pressure is moderate to heavy.

Pine shoot beetle. Those larvae will be pupating and emerging as adults soon. Remove brood material (i.e. trap (sentinel) logs, snags, dead/dying trees) before new progeny adults emerge (210 GDD, Base 10oC) 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.


About Jen Llewellyn

OMAFRA Nursery and Landscape Specialist @onnurserycrops
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