Nursery and Landscape Report for June 26, 2009

The LO Nursery Growers Summer Tour is coming up on Tuesday, July 14 .  This year the group is visiting Sloans Nursery, Downham Nurseries, Heritage Country Gardens, Pieper Nurseries and Agrium Advanced Technologies.  The cost for this a one-day tour is only $55.00 per person.  Register with Kathleen Pugliese at Landscape Ontario (1-800-265-5656 ext. 309).

Environment Canada is calling for sun and cloud today and Saturday.  High’s will be in the mid-high 20’s.  Winds will be from the NW at 10-15 km/hr. Showers are expected for Sunday.

Growing Degree Day summaries are from Environment Canada and are base temperature 10oC.

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 http://www.ene.gov.on.ca/en/land/pesticides/index.php

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.

White grubs are pupating and many 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.

DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:  

Where foliage on outdoor grown ornamentals appears chlorotic (yellow), cold temperatures we experienced a couple of weeks ago may be the culprit.  I received a few calls from growers wondering about yellow foliage.  It is likely not a fertilizer issue, but a result of that cooler weather.  Plants should be greening up with these warmer temperatures.

Monitor for common leaf diseases such as leaf spot and anthracnose on herbaceous perennials and deciduous shrubs (Rosa, Prunus, Cornus).  These leaf diseases are more prevalent under late-day irrigating 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, 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.

Look for thick, white, powdery fungal growth on the newest leaves of Physocarpus opulifolius (especially Diablo, Coppertina).  This is powdery mildew (likely Sphaerotheca sp.) that has been reported widely on our ornamental ninebark.  This fungus sporulates quite profusely on Physocarpus and is difficult to control with fungicides once heavy sporulation is evident.  Remove and destroy infested tips and continue to do so throughout the growing season while protecting new shoots with fungicides (where necessary).

Japanese beetle adults are just starting to emerge (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.  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.

Leafhopper populations are starting to build, they are infesting outdoor ornamentals in many parts of the province (watch your Caragana, Ptelea, Acer) 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.

Wooly beech aphid can be found feeding on the leaf undersides of ornamental beech trees this time of year.  These adelgids can be found underneath the white, waxy material that protects them from pesticide applications.  Worry not!  Wooly beech aphid rarely affects tree health, it is just unsightly.

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 will also become more numerous as the season progresses.  Time insecticide applications (e.g. Tristar for leafhoppers) where monitoring reveals significant populations and injury.  http://oregonstate.edu/dept/nurspest/honeylocust_plant_bug.htm

Oystershell scale (Lapidosaphes ulmi) crawlers have hatched.  Adult scales look like miniature sea shells, often twisted to one side.  They are small scale insects, about 3mm long when mature.  They feed on the twigs of Fraxinus, Acer, Quercus, Malus and Tilia.  Crawlers begin to hatch when the Philadelphus begins to bloom and the Syringa patula ‘Miss Kim’ are in full bloom.  Treat crawlers at PEAK egg hatch, about 7-10 days after crawlers start to hatch.  Try Landscape Oil and insecticidal soap first.  Repeated applications will be required since crawler hatch is staggered.

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 pathogens this week!  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.

Peach tree borer (Synanthedon exitosa) adults are flying. 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

Two-spotted spider mites (TSSM, Tetranychus urticae) are showing up on greenhouse 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.  Miticides registered for this mite in the greenhouse include: DynoMite, Vendex, Shuttle, Floramite, Avid and Kelthane.  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).

EVERGREENS:

Low temperature injury is still quite noticeable on several types of evergreen woody shrubs and trees (e.g. Abies, Picea, Taxus etc.).  Look for brownish black dead, stunted shoots.  Hopefully the next flush of growth should mask this symptomatic foliage.

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, 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.

Check your conifers for raucus weevils.  We have seen Otiorhynchus raucus feeding on the new growth of spruce and buds of eastern white cedar over the last two spring seasons.  Where populations are high, Pounce and Thiodan can help growers manage the adult stages of this weevil.

Small, yellowish, Juniper scale (Carulaspis juniperi) have hatched.  They usually start to hatch when the Kolkwitzia amabalis (beauty bush) is in full bloom and the Catalpa speciosa is in early bloom.  This scale insect in not susceptible to dormant horticultural oil applications in fall or spring so you need to target pesticide applications to the crawler stage or you will miss the opportunity to manage them.  Try summer rates of horticultural oil (e.g. Landscape oil) and insecticidal soaps.  Repeated applications over a 3-week period will be needed to target all hatching nymphs of this scale.

Euonymus scale (Unaspis euonymi) nymphs have settled.  A second generation will hatch in about 4-6 weeks.  Settled nymphs are more difficult to manage, wait for the next generation of crawlers.

A Pine tortoise scale (species to be confirmed) has been found on Scots and jack pine.  You’ll notice reddish brownish “bumps” with white 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 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.

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.

Balsam twig aphid (Mindarus abietinus)nymphs have hatched and can be found feeding on new growth of Abies, causing it to become twisted and chlorotic.  This generation of nymphs is very difficult to manage with pesticides.  Focus pest management efforts on “stem mothers” next spring.

Taxus or Fletcher Scale (Parthenolecanium fletcheri) nymphs are laying their eggs on foliage of Thuja and Taxus.  Look for honeydew and small, brown bumps on foliage, pick off scale and examine the undersides.  If the tissue underneath appear “fleshy”, they are still maturing.  If the undersides are packed with tiny, white grains, they have laid their eggs.  Applications of insecticides are most effective against crawlers (once those eggs have hatched) in a couple of weeks or so.  Repeated applications will be necessary since egg hatch 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.

– See more at: https://lawnsavers.com/nursery-and-landscape-report-2009/nursery-and-landscape-report-for-june-26-2009.html#sthash.vboOEZQV.dpuf