Nursery and Landscape Report for August 19, 2010

You have reached Jen Llewellyn for the 18th edition of the 2010 OMAFRA Nursery and Landscape Report, updated on Thursday, August 19th.

If you or someone you know would like to receive the report FREE online every week, please subscribe online at: http://apps.omafra.gov.on.ca/scripts/english/crops/agriphone/addremove.asp

Mark your calendar for the Annual L.O. Nursery Growers Summer Tour on Tuesday, September 14.  We will be visiting Connon Nurseries CBK Holdings, Blue Sky Nursery, Vineland Research and Innovation Centre, J.C. Bakker & Sons, Mori Nurseries and the Niagara Parks School of Horticulture.  The cost is $65.00 and includes lunch, dinner and refreshments.   To register: contact Kathleen at L.O. (1-800-265-5656 ext. 309).

Environment Canada is calling for continued warm weather with the possibility of showers and thunderstorms this afternoon and evening.  They are forecasting mostly sunny skies on Friday with the possibility of isolated showers on the weekend.   Highs will be around 24-29^oC for the next few days and the relative humidity is going to increase each day.  Winds will be gusting out of the west today and gradually shifting to the north and then east by tomorrow.

Growing Degree Days are to the end of Wednesday, August 18 (GDD 10^oC / GDD 50^oF).  These numbers are only a guide for monitoring purposes. The temperatures at your production facility can vary significantly from the nearest weather station.   Check out: https://climate.weather.gc.ca/?url=http%3A%2F%2Fclimate.weather.gc.ca

Weed ID Online:  http://www.weedinfo.ca/home.php

PLEASE NOTE: 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. There is exception from the ban for the use of pesticides to maintain the health of TREES, if certain conditions are met.  For more info, you can go to the Ministry of the Environment¡¯s website at http://www.ontario.ca/pesticides

VARIOUS ORNAMENTALS:

Monitor for common leaf diseases such as leaf spot and anthracnose on herbaceous perennials and deciduous shrubs (Rosa, Prunus, Cornus) and deciduous trees.  These leaf diseases are more prevalent under late-day irrigation since foliage does not dry off before the evening, prolonging the leaf wetness period and encouraging disease sporulation and infection.  Keep disease-prone ornamentals on a strict, early–mid morning watering schedule to reduce leaf wetness periods and you will notice that the next flush of growth is much nicer.  There are several different fungicides labelled for foliar diseases, including Rhapsody (a biological).

Check for adults of black vine weevil and strawberry root weevil hiding in plants such as Picea, Rhododendron, Taxus, Thuja and Euonymus in field and container (woody and herbaceous) production nurseries and the landscape.  BVW will feed by chewing out notches in leaf margins, they are ~1.5 cm long, black, with mottled brown flecks on their backs.  SRW feed by girdling the bark of small twigs and are ~0.8 cm long, reddish brown.  Adult weevils feed at night but can be found hiding deep in foliage or just under leaf litter during the day and adults ¡°PLAY DEAD¡± in the daylight.  Adult feeding is insignificant but their presence and level of feeding will give you an indication of feeding pressure from the subsequent population of larvae.  In nursery production, Pounce and Thiodan are registered to manage the adult stages of weevils.  Applications of beneficial nematodes are not effective at this time.  The next window for nematodes to target the next generation larvae in soil will be late summer.

Tiger moth caterpillars can often be found feeding on nursery crops this time of year.  These are very fuzzy yellow-to-white coloured caterpillars, often with coloured tufts of hairs on their backs.  In the nursery, these late season leaf-feeding moth larvae can be knocked down with broad spectrum insecticides.  Dipel (Bacillus thuringiensis) is an effective biological approach (although it will take 2-3 days to see mortality).   http://bugguide.net/node/view/39177/bgimage

Japanese beetle adults are still active.  Look for large, coppery-green metallic beetles (13mm long) with distinctive white tufts of hairs around the sides of their abdomen feeding in groups on foliage and flowers.  They are attracted to floral lures and Japanese beetle sex pheromones and can be easily trapped (always use traps as far away from your production blocks as possible) for manual disposal.  The adults will feed on the flowers (Rosa) and foliage (Tilia) of many woody and herbaceous plants.  They lay their eggs in grassy areas and the larval stage feeds on the roots of grass.  If adult populations become economically threatening, applications of Sevin, Malathion or Imidan may be warranted.  Growers: to help qualify for the Japanese beetle certification program, an application of Intercept on container or field stock should be made some time between June and July (notify your inspector first).  The cut-off period for Intercept applications to comply with the CFIA JB Certification program may be as early as July 31^st this year.

Bagworm has been reported widely in the neighbouring United States.  This is a moth whose caterpillar stage feeds on foliage from inside a protective ¡°case¡± that looks like it was made out of tiny bits of wood.  Look for them on cedar, spruce, and several different deciduous hosts including honeylocust and crabapple.  Foliage will turn brown and become quite sparse.  Closer examination may reveal brown cases attached to leaves and twigs and if you wait you will see the larvae move around and stick their heads out of the cases to feed.  Dipel (Bacillus thuringiensis) may still be effective at this stage of larval development.  At the end of the season, ¡°bags¡± can be found on branch tips and resemble small conifer cones.  The bags can be picked off and destroyed in the fall to prevent the next generation from hatching next spring.  Please give me a call if you are seeing this pest.

DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:  

Partial, sudden leaf drop has been reported on deciduous trees in the landscape and also on some crops in the nursery (e.g. Euonymus).  Some of the partial leaf drop is likely in response to extreme heat, humidity and those areas not receiving as much precipitation.  In some cases, spring diseases such as anthracnose have been linked to the dropped leaves.  It is a survival mechanism of the plant and in most cases, does not lead to dieback.

Fireblight is quite active in field production this summer.  Look for sudden dieback of branches with persistent, dark-brown leaves.  Often, the branch tips become curled like a Shepherd¡¯s crook.  You can try bagging symptomatic tissue carefully during dry weather and removing/destroying it immediately but this does not always reduce disease spread.  Copper products should help to protect healthy foliage in the remainder of the field.  Watch the pre-harvest interval on the Streptomycin label.  Fireblight is a very virulent disease.  Bloomtime, Blightban and Serenade Max may help give some disease suppression where disease pressure is low, early in the season.

Powdery mildew is an issue on highly susceptible ornamentals (Amelanchier, Rosa, Syringa) with the hot, dry weather we had.  Monitor for powdery, white residue on the tops of leaves as a symptom of this disease.  Powdery mildew can lead to chlorotic, stunted foliage that may drop prematurely.  Sulphur and copper are exempt for use as fungicides in the landscape.  In the nursery, effective preventative fungicides include Banner MAXX, Compass, Nova, MilStop, Rhapsody (B. subtilis) etc.

Monitor for downy mildew on herbaceous perennials and deciduous shrubs (Rosa, Prunus, Cornus).  Downy mildew is rearing it¡¯s ugly head on field crops around southern Ontario and the Great Lake States so be on the lookout for purplish-red to brown lesions with a downy mass of spores on lesion undersides just after irrigation.  These leaf diseases are more prevalent under late-day irrigating since the foliage does not get a chance to dry before night-time.  The leaf wetness period is more prolonged, encouraging disease sporulation and infection.  Keep disease-prone ornamentals on a strict, early-mid morning watering schedule to reduce leaf wetness periods.  Acrobat fungicide was recently registered to help combat downy mildew on ornamentals.  Bacterial leaf spot may be evident on deciduous shrubs and herbaceous perennials.  Bacterial leaf spot looks purplish red spots that are often delineated by leaf veins.  It looks a lot like downy mildew but there is no fuzzy growth (sporulation) on lower leaf surface when you hold it is a moist baggie (or just after irrigation).  Bacterial diseases may be suppressed with copper fungicides and reduced leaf wetness periods.

Pear trellis rust (Gymnosporangium fuscum) is evident on pear trees this year in the landscape.  Look for bright orange-red lesions on the tops of pear leaves.  It is too late to do anything about this disease, leaves were infected during warm, wet conditions in May (from infected Juniperus sabinae, the overwintering host).

Take a close look at the foliage of Norway, silver and red maples for halos that are filled in with tiny, black spots.  This is tar spot on maple.  The tiny, black, tar-like spots that make up the larger circular black lesion are the fruiting structures that will produce spores next spring).  Fungicides are ineffective at this time of year.  The lesions show up so late in the season that they have little effect on tree health, but may be a symptom that the tree is under stress.

Magnolia scale is rampant this year and there have been several calls of very high populations in the landscape.  Right now, magnolia scale appears as large, pinkish-orange scales.  They have laid their eggs and those crawlers have hatched.  Pick off the scale insect and look at the underside for tiny, white grains, those are the eggs.  You may also find the crawlers under the parent scale.   Look with a hand lens to see if egg cases are empty (hatched).  Crawler hatch usually starts late July to early August (~1200 GDD 10^oC).  If you want to try insecticides against the crawler stage, make sure you are making at least 3 repeated applications, 7 days apart.  This will have much better knockdown since crawler emergence is staggered.  Insecticidal soap and the summer rate of horticultural oils should give good knock down.  Malathion, Orthene and Sevin are registered for this pest in the nursery.

Beech Scale crawlers will be hatching soon (from early August to mid-September). Adult females are covered in a white, wooly mass when mature and so they are easy to monitor this time of year.  Beech scale can be found on the bark of large beech trees (¡Ý 40cm DBH), mostly on the trunk and on the major limbs.  Although the scale insect does not kill the tree, beech scale seems to predispose the tree to other problems and create wound sites that facilitate the entry of beech bark disease (Nectria coccinea var. faginata).  Beech bark disease is a devastating fungal disease that has caused the death of several native and introduced beech trees in Ontario.  So far, the scale and the disease have been found in beech forests throughout much of southern Ontario (including cottage country).  Monitor scale populations for crawlers and treat crawlers about 3 times, every 7-10 days to target staggered emergence.  Use insecticidal soap and Landscape Oil or other registered chemical insecticides when peak hatch occurs, in the next couple of weeks or so.  Fall and spring (dormant) applications of horticultural oil may also reduce beech scale populations.

Leafhoppers: nymphs and adults are still be feeding on crops.  Monitor for leafhoppers (such as potato leafhopper) on nursery crops such as Caragana, and Acer, especially after forage crops have been cut on neighbouring farms.  Leafhopper 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. Adults blow in from the south and prefer to feed and lay their eggs on newly expanding leaf tissue, especially the 2^nd flush in June.  Leafhopper nymphs are tiny, flightless, yellow-green insects that move sideways, very rapidly across the leaf. Leafhoppers suck plant sap from expanding foliage and cause foliage to wilt, become off-coloured and eventually curl and become stunted with brown-black margins (¡°hopper burn¡±). Leafhopper injury also appears as bronzing or stippling on more mature leaves.  Monitor populations and treat with insecticides before damage becomes economically threatening.  Leafhoppers are also attracted to yellow sticky cards, for monitoring purposes.  Registered insecticides for nursery production include Tristar and Sevin XLR.

Fall webworm nests are quite noticeable on tree branches.  They can be seen on Betula (birch), Fraxinus (ash) and Juglans (esp. black walnut), Prunus (cherry) and Malus (apple, crabapple) etc.  Look for webbed tents on the ends of branches with fuzzy, cr¨¨me-coloured caterpillars inside.  The tents can be easily pruned out and destroyed (e.g. squished).  Pruning out infested branches can be quite effective right now since there are multiple generations of this pest through late summer.  Chemical pesticides are virtually ineffective because of the tough web.  Keep in mind that many predators, parasites and pathogens attack fall webworm.  Damage from the fall webworm is usually insignificant to tree health, late in the season.  Telescoping pruners can be an excellent tool for IPM in the landscape.

Monitor evergreen Euonymus for the second generation of Euonymus scale crawlers in the landscape.  Also, monitor for the second generation of Pine needle scale crawlers on Austrian, Mugo and Scots pine.  Repeated applications of insecticides will be necessary as emergence is staggered, especially with the 2^nd generation.

European fruit Lecanium scale crawlers are settling and much less susceptible to pesticides at this time.  Look for adults: reddish brown bumps on the twigs of deciduous trees such as Quercus, Fraxinus and Acer.  Crawlers are tiny, pale tan and have settled on feeding sites and are developing a protective waxy coating.

Emerald ash borer adults may still be flying in south western Ontario.  TreeAzin (azadirachtin, neem) has an emergency use registration (until August 31) for emerald ash borer on ash.  This is an injectable insecticide that is delivered though BioForest¡¯s Ecoject system, to inject insecticides to help protect ash trees from this borer.  For more information contact BioForest (http://www.bioforest.ca/).

The regulated areas for Emerald Ash Borer can be found at: http://www.inspection.gc.ca/english/plaveg/pestrava/agrpla/survenqe.shtml

We found spider mites on leaves of Quercus this time last year in nursery production.  Check for teeny-tiny mites that are orange with black backs (visible with magnification).  They have caused bronzing on the foliage in past years.  It looks like they are in the genus Oligonynchus (spruce spider mite, maple spider mite) and they look very similar to the maple spider mites we find on red-silver hybrids this time of year.

Look for honeylocust spider mite on cultivated honeylocust (Gleditsia).  These orange mites can be found feeding on leaf undersides in late summer.  Where damage is causing leaf drop and dieback in the nursery, a miticide application may be warranted.

Two-spotted spider mites (TSSM) are active on greenhouse and field grown ornamentals (woody and herbaceous).  They love this hot weather and populations can increase dramatically within a week or so.  Use your hand lens to see tiny, clear bodied mites with dark regions (may be faint black) on their backs, on the UNDERsides of leaves.  The upper surface of leaves appears as stippled and slightly chlorotic.  These mites are small but the damage is significant so catch them early.  Miticides registered for this mite in the greenhouse include: DynoMite, Vendex, Shuttle, Floramite, Avid and Kelthane.  Miticides registered for this pest on nursery crops include: Apollo (eggs and newly hatched nymphs), Floramite, Vendex, Dyno-Mite, Kanemite, Forbid, Kelthane.

EVERGREENS & CONIFERS:

We saw White Pine Blister Rust sporulating on the lower leaf surfaces of Ribes (currant) this week in Guelph.  This host is responsible for new infections on white pine in late summer each year.  White pine blister rust is known to cause lethal branch and stem cankers on white pine in the nursery, landscape and forest.  There are no fungicides registered for this disease in Canada. Keep currants far away from your white pine crops.  When white pine is dormant, prune out and destroy cankered branches to help reduce disease incidence and progress.  Unfortunately, once cankers reach the main stem tree mortality is unavoidable, remove and destroy all above-ground tissue when plants with trunk cankers are dormant.

For those of you growing Scots and Austrian pine, Lophodermium needlecast could be starting to sporulate in your production area.  Look for brown, fallen needles with tiny, black football-shaped fruiting bodies running the length of the needle.  Where more than 10% of the trees are infested, Michigan State University recommends fungicide applications during warm, humid weather in August and September.  Registered fungicides to help protect healthy tissue include Copper spray, Daconil, Dithane and Manzate.

Are you seeing dead tops (a.k.a leaders, terminal shoots) on spruce and pine?  It could be from white pine weevil larvae, tiny, white, legless larvae that were boring inside terminal shoots in June and July.  White pine weevil larvae are emerging as adults, congregating on their hosts to do a bit of feeding before they overwinter.  It¡¯s too late to do anything about this pest but you can prune out damaged tips and start training a new leader.

Taxus or Fletcher Scale (Parthenolecanium fletcheri) crawlers are starting to settle on foliage and twigs of Thuja and Taxus.  Look for honeydew, black sooty mould and small, brown bumps (dead adult females) on foliage. Applications of insecticides are not nearly as effective against settled nymphs as they were for the crawlers.  In the nursery, systemic insecticides may be warranted where populations are significant.

Cedar leaf miner larval populations were very damaging this spring.  The next generation of larvae are feeding inside the tips of foliage.  Applications of systemic insecticides and pruning infested tips should be targeted for early-mid August to catch the next generation of young larvae.

Monitor for nymphs and adults of spruce spider mite on conifers with a history of mite damage.  SSM nymphs are tan coloured with dark backs, and move at a moderate pace. Adults have darker black backs. Miticides registered for this pest include Kanemite, Floramite and Vendex.  In field production, SSM populations usually go dormant (egg stage) in the heat of the summer.  However in container production, SSM may stay active all summer (probably due to cooling effect of overhead irrigation).

– See more at: https://lawnsavers.com/nursery-and-landscape-report-2010/nursery-and-landscape-report-for-august-19-2010.html#sthash.VJaLWauE.dpuf