Nursery and Landscape Report for October 13, 2009

Environment Canada is calling for the cooler weather next week.  Check your local weather for frost warnings.

Growing Degree Day summaries are from Environment Canada and are base temperature 10oC (Oct 1).

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°C (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—absorption 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.

With autumn mowing practices you have the opportunity for the cultural control of many tree diseases (and help discourage voles and mice from nesting near your trees). All those infected leaves dropping from the maples, oaks and crabapples are carrying fruiting structures that will be a source of disease next spring.  Research has shown that mowing/mulching fallen leaves regularly (e.g. weekly) and applying a light irrigation (and some water soluble nitrogen that is part of your fall fertilizer program) will help accelerate the breakdown of those diseased leaves over the autumn months.  This means a significant reduction in the amount of fruiting structures that can start off the disease cycle next spring.  Kevin Frank of Michigan State University suggests keeping mower blades sharp since leaves can be tougher than grass.  Raise the mower height up and mow leaves when they are lightly wet (e.g. morning dew).  This will keep the leaves from blowing all over and will prevent the mower from getting bogged down in wet leaves.  The decomposing leaf litter is an excellent source of slow release nutrients and organic matter for your lawn or cover crop.

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.  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 autumn where container media temperatures are still warm (above 10oC).  Soils will likely be a little too cool by now until you can use Steinernema kraussei.

DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:  

Fireblight was bad in some production areas this summer.  It’s no surprise that this was a fairly significant 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.  Pruning during warm autumn weather could still lead to new infections.  Wait until plants go dormant and prune well below the symptomatic tissue.  Better still, prune in late winter.

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 crème 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, crème-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.

This is a great time of year to monitor for Eastern tent caterpillar egg masses.  Monitor Prunus, Malus and Crataegus on sunny days once the leaves have dropped.  Look for shiny, silver thickened bands around current season’s twigs.  Prune out and destroy to prevent all those messy larval tents and defoliation next spring!

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. <28oC) or freezing temperatures are in the forecast.

EVERGREENS:

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.

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.

– See more at: https://lawnsavers.com/nursery-and-landscape-report-2009/nursery-and-landscape-report-for-october-13-2009.html#sthash.GTATXL1A.dpuf