Nursery and Landscape Report for July 10, 2009

Environment Canada is calling for showers and possible thunderstorms to roll in late tonight and stick around until tomorrow evening some time (later in the east).  Winds will be from the SW or S gusting up to 20km/hr this afternoon and 30km/hr tomorrow morning. Saturday and Sunday will be cooler and much less humid, high’s are expected to be around 22-25oC for much of the weekend, night time lows will also be cooler (around 10oC).

Growing Degree Day summaries are from Environment Canada and are base temperature 10oC (July 7).

The Pesticides Act has been amended by the Cosmetic Pesticides Ban Act, 2008 and Ontario Regulation 63/09 that have taken effect on April 22, 2009.  For more information on the legislation call the Minitry of Environment information line at: 1-800-565-4923 or see the Ministry of the Environment’s website at

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.

VARIOUS ORNAMENTALS:

Check for adults of black vine weevil and strawberry root weevil on crops such as Picea, Rhododendron, Taxus, Thuja and Euonymus in field production nurseries and the landscape.  BVW are about 1.5 cm long, black, with mottled brown flecks on their backs.  SRW are about 0.8 cm long, reddish brown.    Adult weevils can be found hiding deep in foliage or just under leaf litter during the day.  In nursery production, Pounce and Thiodan are registered to manage the adult stages of weevils.  Applications of beneficial nematodes are no longer effective at this time.  The next window for nematodes to target the next generation larvae in soil will be September.

European chafer adults are flying where the Tilia cordata are blooming.  Look for brown beetles swarming and buzzing at sunset.  May/June beetle adults have already emerged.  Preventative applications of Intercept (imidacloprid) are registered for white grubs in nursery production.  The application period is late June and July (to coincide with egg-laying).  Nematode applications for white grubs are not effective at this time.  Try timing nematode applications for late August/early September to catch early instar larvae.

Look for long-legged, bronze coloured beetles feeding on roses, crabapples and other woody ornamentals in the coming weeks, these are Rose chafers (Photo: http://www.uwex.edu/ces/wihort/flowers/RoseChafers.htm).  Try shaking beetles into a bucket of soapy water, this will smother them.  Contact insecticides (e.g. Sevin) will reduce populations where this pest is a major problem in the nursery.

Summer rate applications of horticultural oil (e.g. Landscape Oil) may be used (where permitted) so that treated foliage dries before the heat of the day.  To avoid phytotoxicity, try to apply oils once leaves have hardened off (where possible) and avoid applications on hot days.  Some uses of summer oil include:  scale insect crawlers, European red mites and mealybugs.

DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:  

Monitor for common leaf diseases such as leaf spot, anthracnose and downy mildew on herbaceous perennials and deciduous shrubs (Rosa, Prunus, Cornus).  These leaf diseases are more prevalent under late-day irrigation since the leaf wetness period is more prolonged, encouraging disease sporulation and infection.  Keep disease-prone ornamentals on a strict, mid-morning watering schedule to reduce leaf wetness periods and you will notice that the next flush of growth is much nicer.

Euonymus anthracnose is sporulating and infecting the second flush of growth on container grown euonymus.  Ensure good fungicide coverage before warm, humid nights.  Daconil is registered for this disease.  Anthracnose appears as a leaf spot (usually late summer) and stem canker and can be quite serious on variegated cultivars of Euonymus fortunei.

Powdery mildew is becoming evident on highly susceptible ornamentals (Amelanchier, Physocarpus, Rosa, Syringa) right now.  Look for powdery, while 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 fungicides include Banner MAXX, Compass, Nova, MilStop, Rhapsody (B. subtilis) etc.

Japanese beetle adults have emerged (where the Tilia cordata are blooming).  Look for large, coppery-green metallic beetles (13mm long) with distinctive white tufts of hairs around the sides of their abdomen.  I’ve had a few people report groups of JB’s forming small balls on the ground. They are very attracted to floral lures and Japanese beetle sex pheromones and can be easily trapped 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 plants.  If adult populations become economically threatening, applications of Imidan, Sevin and Malathion may be warranted.  Growers: if you think a drench of Intercept will be needed to allow shipping of nursery stock outside your JB zone, make sure you are carrying out applications in the next 4-6 weeks.

We have seen significant leafhopper populations in nursery crops this week (watch your Caragana, Ptelea, Acer-especially red-leaved cultivars of A. platanoides) especially after forage crops are cut.  Each year I receive calls of injury on Acer in the mid-summer and quite often, late spring leafhopper injury is to blame.  Leafhoppers (and aphids) that feed on expanding foliage will cause it to twist and become shrunken and distorted.  Leafhoppers injury also appears as bronzing or stippling to mature leaves.  Monitor populations and treat with pesticides before damage becomes economically threatening.  Leafhoppers are very mobile, tiny, pale coloured jumping insects that are easily disturbed when you approach infested foliage. Leafhoppers are also attracted to yellow sticky cards, for monitoring.  Registered insecticides include Tristar and Sevin XLR.

We’ve noticed quite a significant population of aphids in the landscape and on outdoor nursery stock this year.  There are several species that can be found feeding on the stems and leaves of woody and herbaceous plants.  There is a species of aphid (black with white lines on the back) that we are finding widely across southern Ontario, it has been detected on several species of woody deciduous shrubs and trees.  Insecticidal soap may help reduce populations of aphid, repeat applications at least weekly to give good knockdown.  In the nursery, several insecticides are registered to manage aphids on ornamental crops.

The honeylocust plant bug has taken it’s toll on honeylocust foliage this year.  Their feeding causes twisting, mottled and defoliated stems. You will find nymphs and adults of this tiny green insects infesting honeylocust right now.  Honeylocust leafhoppers are also become more of a problem as the season progresses.  Time insecticide applications (e.g. Tristar for leafhoppers in the nursery) where monitoring reveals significant populations and injury.  http://oregonstate.edu/dept/nurspest/honeylocust_plant_bug.htm

Scale insects are pretty bad in some areas.  Monitor evergreen Euonymus for the second generation of Euonymus scale crawlers in the next couple of weeks.  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 2nd generation.

Gypsy moth (Lymantria dispar)larvae can be found feeding on several different kinds of plants right now.  They are 2.5 to 5 cm long, dark, fuzzy larvae and are especially fond of Quercus, Tilia and Ulmus.   You will be able to see the blue and red dots on their backs.  We are seeing some larval death due to natural pathogens!  Dipel is not as effective with these larger larvae, especially after the head capsule turns yellow.  Try spinosad (Success) insecticide to manage more mature lavae.  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.  Homeowners will need to inspect burlap skirts and underlying bark crevices daily (1-3 pm is best) and remove/destroy larvae.

We found spider mites on leaves of Quercus this week.  Check for teeny-tiny mites that are orange with black backs (visible with magnification).  They are causing bronzing on the foliage.  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.

Two-spotted spider mites (TSSM, Tetranychus urticae) are showing up on field grown ornamentals (woody and herbaceous).  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. TSSM overwinter as adult mites in the soil and crawl up on host plants and start feeing in late spring.  Where the egg stage is present, Apollo (an ovicide) is available to help reduce populations of eggs and newly hatched nymphs. Miticides registered for this mite in the greenhouse include: DynoMite, Vendex, Floramite, Forbid and Kelthane.

Peach tree borer (Synanthedon exitosa) adults are flying in container grown Prunus. Look for cankered regions and chewed bark/wood in the lower stems of Prunus x cistena (and other Prunus spp.) 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 are also starting to emerge in container production at this time.  To purchase pheromones, try ordering from IPM suppliers such as www.greatlakesipm.com and www.naturalinsectcontrol.com.

Emerald ash borer adults are flying.  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 protect ash trees from this borer.  For more information contact BioForest (http://www.bioforest.ca/). The regulated areas for Emerald Ash Borer have been updated (it has most recently been found in Welland). The movement of potentially infested material is restricted in four new areas that are regulated under Ministerial Orders. In Ontario, these areas include Toronto and surrounding areas, Sault Ste. Marie, and Ottawa and its neighbouring city, Gatineau, Quebec. A new Ministerial Order is also in place for Carignan, Quebec, and its surrounding municipalities.  Check out: http://www.inspection.gc.ca/english/plaveg/pestrava/agrpla/survenqe.shtml

EVERGREENS:

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 closely at 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, 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.

Striped pine scale (Toumeyella parvicornis) has been found on Scots and jack pine.   You’ll notice reddish brownish “bumps” with white mottled stripes along the twigs and copius amounts of honeydew and black sooty mould.  Crawlers are hatching and can be managed with contact insecticides.  In the landscape try repeated applications of insecticidal soap and the summer rate of horticultural oil where labelled

White pine weevil larvae (Pissodes strobi) will be feeding from inside the shoots (terminals) on pine and spruce.  Terminal shoots become brown, flagged or crooked right about now.  Prune out infested shoots down to the original bud and destroy them to prevent the successful emergence of the next generation.

Pine false webworm (Acantholyda erythrocephala) larvae are snipping off foliage and making 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.

Look for adelgids that have laid their eggs on the new needles of larch.  These eggs will be hatching in the next week or two, newly hatched nymphs are very susceptible to insecticides.  The nymph adelgids feed openly on new needles, causing them to twist and become chlorotic.

Look for yellow headed spruce sawfly on spruce.  Sawfly larvae are very susceptible to chemical control when they are still young.  Try Success (spinosad) as a lower toxicity alternative.

Red-headed pine sawfly are feeding on new growth of pine.  When threatened, the larvae will simultaneously rear up on their end and form an “S” shape.  Small infestations can be removed manually.  Contact insecticides are registered for this pest (e.g. Success 480 SC).

Spruce spider mites (Oligonychus ununguis) can be found feeding on new growth of conifers (Abies, Picea, Pinus, Thuja etc.).  Use lots of water and pressure, try to coat undersides of twigs and foliage.  Kanemite, Floramite and Vendex are registered for use against spruce spider mite.  If you are using Kelthane, treat water if pH > 7.0 as alkaline water will decrease efficacy of Kelthane.

Taxus or Fletcher Scale (Parthenolecanium fletcheri) crawlers are active on foliage of Thuja and Taxus.  Look for honeydew and small, brown bumps on foliage, pick off scale and examine the undersides.  If the undersides are packed with tiny, white grains, they have laid their eggs.  Applications of insecticides are most effective against crawlers and repeated applications will be necessary since egg hatch and crawler emergence is staggered.

Cedar leaf miner (Argyresthia sp) larvae have pupated and tiny, grey adult moths can be found fluttering around foliage.  Foliar applications of systemic insecticides are much more effective when applied to the next generation of young larvae (August).  A light sheering of foliage in late August will also help reduce the number of larvae that successfully overwinter.

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