Nursery and Landscape Report for September 26, 2008

You have reached Jen Llewellyn for the 21st edition of the 2008 OMAFRA Nursery and Landscape Report, updated on Friday, September 26th.

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The 30^th annual Canadian Greenhouse Conference is coming to the International Centre (near Pearson / Toronto airport) October 8 and 9^th. 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 (http://www.weatheroffice.gc.ca/forecast/canada/index_e.html?id=ON) is calling for sunshine today, there is a 40-60% chance of showers for Saturday but the sun will return on Sunday (except in the East where there is still a chance of showers on Sunday).  High¡¯s will be in the low 20¡¯s and night-time lows will be in the mid-teens.  Intellicast¡¯s radar (http://www.intellicast.com/National/Radar/Current.aspx) is a clear slate for southern Ontario today.

Growing Degree Day accumulations to the end of Thursday, September 25 (GDD 10^oC / GDD 50^oF).(Courtesy of those nice folks at the Weather INnovations Incorporated (WIN): http://www.weatherinnovations.com/index.cfm).  These numbers are only a guide for monitoring purposes. The temperatures at your production facility can vary significantly from the nearest WIN weather station.

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.

Rodent bait for vole control should be placed out by now 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 to rotate 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.

DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:  

Take a close look at the foliage of Norway (also silver and red maples) for large, black spots.  These are tar spot lesions.  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 and may be associated with premature leaf drop.

Where Gymnosporangium rust was detected on ornamental Pyrus in the landscape this summer, look for bright orange-red lesions on the tops of leaves and bumps on the underside.  Cr¨¨me-coloured sporulation on the undersides of leaf lesions will appear in the next few weeks or so and will send out spores to infect Juniperus.  Pear Trellis Rust has been confirmed on several ornamental Pear trees in the Toronto area last year and is likely the species present in many other areas as well.  This disease does not overwinter on Pyrus, it overwinters on the Juniperushost.

I¡¯ve had a few inquiries about fireblight this summer.  It¡¯s no surprise that this was a really bad year for this disease.  A lot of people are wondering what they can do to improve the look of the trees.  Science says to hold off on pruning.  Because of the warm weather, pruning could still lead to new infections.  Wait until plants go dormant and prune well below the symptomatic tissue.  Better still, prune in late winter.

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

Honeylocust spider mite has ramped up on Gleditsia in production nurseries and in the landscape.  Mites are very tiny (similar to TSSM) with clear-tan bodies.  We have seen this mite in production nurseries in previous years, especially in hot, dry summers.  Where populations are high, mite injury could cause significant stippling, bronzing and defoliation may result.  It¡¯s getting too late to warrant pesticide applications this year, start monitoring for this mite in July next year.

Are you seeing mite injury on Acer rubrum, Acer x freemanii (e.g. ¡®Autumn Blaze¡¯, ¡®Jeffersred¡¯)?  Mite injury appears as bronzing and flecking on the top sides of leaves.  Look at the bottom leaf surface and check for tiny, pinpoints or specks.  You¡¯ll need to get your hand lens out.  Recently we have discovered populations of ¡°maple spider mite¡± in at least 2 areas of southern Ontario.  Maple spider mite (Oligonychus aceris) looks exactly like spruce spider mite: black backs, brown legs and head and they lay red, spherical eggs but it feeds on maple leaves.  They can cause major leaf stippling and sometimes the injury results in leaf drop and poor fall colour.  It¡¯s getting too late to warrant pesticide applications this year, start monitoring for this mite in July next year.

Fall webworm nests are very common on deciduous trees (e.g. Juglans, Fraxinus, Prunus, Malus) in the landscape this year.  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).  Chemical pesticides aren¡¯t going to help much (webworms stay in their protective tents and only come out to make a new tent).  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.

Magnolia scale adults are dead but are still clinging to twigs as orangy-pink bumps.  If you pick them off, you will see tiny white grains (empty egg cases).  Crawlers are small, black specks and have settled at permanent feeding sites on twig undersides.  Fall applications of horticultural oil can help smother this scale and help knock down populations.  Avoid horticultural oil applications when high temperatures (e.g. >28^oC) or freezing temperatures are in the forecast.

Beech Scale crawlers should be crawling (from mid-late August to mid-late 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 applications of dormant oil may also reduce beech scale populations.

Aphid populations usually start to explode this time of year.  The good thing is that their predators/parasites populations are usually pretty significant as well.  Aphids love to feed on the soft, succulent new leaves.  Quite often they hide on the leaf undersides or inside coiled up leaves.  A sure sign of aphid infestation is the presence of ants and ladybird beetles.  Injury is not as significant this late in the season.  If predator/parasites don¡¯t seem to be around, several insecticides will knock down aphids, some newer products include Endeavor and Tristar.  Some softer alternatives include insecticidal soap.

There are several more sites for Emerald ash borer infestation in Ontario, most recently in Vaughan and Sault Ste. Marie,  http://www.inspection.gc.ca/english/plaveg/pestrava/agrpla/survenqe.shtml

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.

VARIOUS HOSTS:

Black vine weevil and Strawberry root weevil adults are still feeding on evergreens and perennials in the field and landscape. Adulticides registered for root weevils include Pounce, Sevin and Thiodan. Where black vine weevil larvae are a problem in container production (e.g. perennials, evergreens), now is a great time to treat with Heterohabditis bacteriophora (BGreen) or Heterohabditis megidis (NemasysH).  This should result in a significant reduction of larval populations in containers and in the landscape.

There are still some distinct areas around Lake Ontario where Gypsy moth populations are high.  Blue Colorado spruce seemed to be a significant host in the landscape again this year (a sign that the insect is over populated).  Some of this year¡¯s larvae fell victim to fungal and viral diseases with the cool, wet weather we received in late spring.  Manual removal of GM egg masses can help reduce populations for next spring, but many of these egg masses are also laid quite high on the tree trunk, out of reach.  (Something to consider if you are thinking of an egg mass removal program).

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://ppathw3.cals.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.

The next generation of larvae of the cedar leaf miner are feeding inside the current season¡¯s foliage.  Foliar applications of systemic insecticides (to target mining larvae) are becoming less effective as larvae are preparing for winter diapause.  Where insecticide applications are not possible, try a light sheering (pruning) of branch tips to help prevent the young larvae from completing their life cycle.

Spruce spider mites are feeding on conifers (Abies, Picea, Pinus, Thuja etc.).  You will require a hand lens to see them better.  Adults are tan brown with black backs, nymphs are more orange.  Use lots of water and pressure, try to coat undersides of twigs and foliage.  If you don¡¯t see much activity, monitor in September/October when temperatures cool down¡­.fall is a major feeding period for this mite.  Kanemite (Shuttle) 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.  Floramite can be used for SSM on Christmas trees in Canada.

THIS MESSAGE WILL BE UPDATED the week of October 10th.

– See more at: https://lawnsavers.com/nursery-and-landscape-report-2008/nursery-and-landscape-report-for-september-26-2008.html#sthash.oeC0QkDr.dpuf