Nursery and Landscape Report for September 25, 2009

The 31st annual Canadian Greenhouse Conference is coming to the International Centre (near Pearson / Toronto airport) October 7 and 8th. The program includes pre-conference tours, sessions related to the production of greenhouse ornamentals and vegetables and there is also a trade show. For more information please check out their web site at http://www.canadiangreenhouseconference.com/.

Environment Canada is calling for cooler, cloudy weather.  There is a good chance of showers for Saturday morning and Sunday in many areas.  High¡¯s expected to be in the range of 15-18oC.

Growing Degree Day summaries are from Environment Canada and are base temperature 10oC (Sep 22).

Up to half of the annual fertilizer requirement may be applied to field and landscape plants, after top growth ceases (mid-September to mid-October).  Autumn is a major root growth period for woody and herbaceous perennials.  Roots will grow and absorb nutrients whenever soil temperatures remain above 5¡ãC (conifers will grow at even lower temperatures).  Environmental cues like temperature, day length and light intensity will stimulate plants to prepare for dormancy – late season root growth and storage is part of that process.  It is not advisable to apply fertilizer in late fall or winter¡ªabsorption will be limited due to cold soil temperatures and fertilizer can be lost through runoff.

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 Ministry 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.

Now is the time to start putting out rodent bait for vole control in the nursery and landscape (especially where container plants are pot tight).  With all the seeds and fruit available this time of year, rodents are beginning to breed heavily and build up their numbers for the winter months ahead.  By putting out bait in September, you can prevent populations from getting out of control.  Place bait stations in areas known to be infested such as grassy fence rows, weedy patches and walkways between containers and polyhouse frames.  Try to have about 10 bait stations per acre of production area.  Remember torotate zinc phosphide baits with other baits (e.g. bromidialone, brodifacaum, defethalone) since the voles will become bait shy with repeated use of zinc phosphide.  Where large areas of field production exist, broadcast application of baits may give some control where tunnels and past damage are evident.

VARIOUS ORNAMENTALS:

Bagworm has been reported widely in the neighbouring United States.  This is a moth whose caterpillar stage feeds on foliage from inside a small, protective case or ¡°bag¡±.  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 small, 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 bags to feed.  Dipel (Bacillus thuringiensis) is not likely as effective this late in the season as larvae will be pupating soon.  At the end of the season, bags can be found on branch tips and resemble small conifer cones. Those bags contain the pupating larvae and later, the overwintering stage of the females (eggs) and can be picked off and destroyed to reduce populations next spring.  Please give me a call if you are seeing this pest. http://ohioline.osu.edu/hyg-fact/2000/2149.html

Check for adults and larvae 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.  Applications of beneficial nematodes (e.g. Heterohabditis bacteriophora) are effective against the early larval stages in mid-late September where soil/media temperatures are warm (above 10oC).

DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:  

Pear trellis rust (Gymnosporangium fuscum) is quite evident on pear trees this year in the landscape.  Look for bright orange lesions on pear leaves, these are getting larger each week.  It is too late to do anything about this disease, leaves were infected during warm, wet conditions in June (from infected Juniperus sabinae, the overwintering host).  Lesions are very unsightly and sometimes lead to premature leaf drop.  Lesions will produce cr¨¨me coloured structures on leaf undersides in late summer and send spores to the alternate Juniper host.  Once the pear leaves drop, the tree is no longer infected.  Annual infection of pear depends on the alternate host, Juniper, sporulating nearby in the spring.  Keep trees healthy and where possible, protect with fungicides during sporulation period of Juniper host.  http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2007/23hrt07a2.htm

Take a close look at the foliage of Norway, silver and red maples for tar spot.  Large, black, tar-like spots (these are the fruiting structures that will send up spores next spring) are quite obvious this time of year.  Fungicides are ineffective at this time of year (infection took place in spring).  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.

Viburnum leaf beetle adults have laid their eggs on the twigs of Viburnum.  Look for holes and skeletonised foliage on Viburnum.  Turn the new twigs upside down and you will see rows of brown, bumpy caps on the underside of the green twig.  Pick off the bumpy caps and you¡¯ll see the tiny yellow eggs tucked down inside the twig.  By pruning out infested twigs, you can reduce the population of hatching larvae next spring.

Birch Catkin bug has been quite prolific on several birch trees in southern Ontario landscapes in the last few years.  This plant bug is tiny (about 4 mm long) with an ¡°X¡± on their membraneous wings (you¡¯ll need a hand lens to see the x).  They can be found in large groups, feeding on the catkins (and the seeds inside) of birch trees.  They are just a nuisance and do not cause any harm to the tree.   http://www.extension.umn.edu/distribution/housingandclothing/M1181.html

Tiger moth caterpillars can often be found feeding on nursery crops this time of year.  These are very hairy, 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 3 or 4 days to see mortality).    http://bugguide.net/node/view/160

Fall webworm nests are quite noticeable on deciduous trees (e.g. Fraxinus).  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 since there are multiple generations of this pest.  Chemical pesticides may give some reduction in webworm populations (webworms hide in the tents during the day and feed at night).  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.

Magnolia scale crawlers are starting to settle.  If you want to try insecticides for the crawlers, make sure you are making at least 3 repeat 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 nymphs are hiding under tiny, white wooly masses on the trunks of large beech trees. They are not as susceptible to horticultural oil as the wooly layer protects them.  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).

EVERGREENS:

Look for defoliation of last year¡¯s needles on pines (Scots, Austrian, red) as a sign of Lophodermium needlecast.  Affected foliage is found primarily at the base of the tree.  Fallen, diseased needles will be brown with football-shaped black fruiting structures on them.  These fruiting structures will produce spores that infect the newest growth from now until the beginning of autumn.  Protect new growth with applications of Copper Spray, Daconil and Dithane starting now until the end of September.  Sporulation takes place when conditions are warm and wet.   http://www.plantpath.cornell.edu/Trees/LophNcst.html

Adults of Pales weevil are active.  These reddish-brown weevils will feed briefly on twigs of pine (especially Scots pine) and other conifers and are susceptible to contact insecticides (Sevin 50W) at this time.  Cornell University suggests monitoring for adult weevil activity by placing freshly cut pine discs around the base of trees that attract adult weevils for monitoring during daylight hours.  High populations of adults will cause some twig girdling and flagging.  The bulk of the injury is carried out by the larvae, which feed on underground stems and roots.

Spruce spider mites (Oligonychus ununguis) can be found feeding on new growth of conifers (Abies, Picea, Pinus, Thuja etc.).  The fall is a time when spruce spider mites do a lot of feeding on the current season¡¯s needles.  Often this damage is noticed until next spring.  NOW IS THE TIME to manage spruce spider mites on evergreens.  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 in the nursery.  If you are using Kelthane, treat water if pH > 7.0 as alkaline water will decrease efficacy of Kelthane.  Horticultural oil is available for use on some evergreens.  Avoid horticultural oil applications on white pine.  The blue hue may be removed when applied to blue cultivars of juniper and spruce.  Injury on eastern white cedar has been reported from time to time but is often associated with improper agitation, rate and extreme temperatures after the horticultural oil was applied.

Taxus or Fletcher Scale (Parthenolecanium fletcheri) NYMPHS are feeding on foliage of Thuja and Taxus.  Look for honeydew and small, flat, light brown oval scales on foliage.  Applications of insecticides are most effective against newly hatched crawlers and repeated applications will be necessary since egg hatch and crawler emergence is staggered.

Cedar leaf miner (Argyresthia sp) early instar larvae are starting to feed inside tips of Eastern white cedar.  A light sheering of foliage may help reduce the number of larvae that successfully overwinter.   Galls of Eastern and Cooley Spruce Gall Adelgid are more noticeable as they have turned brown.  The immature adelgids that feed inside the galls until late summer when winged adults emerge and galls turn brown.  A fall application (when sugar maples turn yellow) of horticultural oil to the undersides of branches will help smother the overwintering stage of nymphs.

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