Nursery and Landscape Report for July 4, 2008

You have reached Jen Llewellyn for the 13th edition of the 2008 OMAFRA Nursery and Landscape Report, updated on Friday, July 4th.

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Environment Canada (http://www.weatheroffice.gc.ca/forecast/canada/index_e.html?id=ON) is calling for a beautiful, warm, sunny weekend.  High’s are expected to reach 25-28^oC in much of southern Ontario.  Winds be light and out of the NE/E and switching to the S on Sunday.  Intellicast’s radar (http://www.intellicast.com/National/Radar/Current.aspx) is looking nice and clear to the southwest of us.

Growing Degree Day accumulations to the end of Thursday, July 3rd (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.

DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:  

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.

Where the second flush of growth is emerging on euonymus (container or field grown), continue to protect new foliage with fungicides until the new growth hardens off.  Euonymus anthracnose causes a leaf spot and stem canker (stem dieback) on many of the variegated cultivars of euonymus (Emerald Gaiety, Emerald ‘n Gold).  The anthracnose is a weak pathogen that preys on succulent or damaged tissue (e.g. pruned tissue) and persists in foliar litter and diseased tissue from last year.  Anthracnose is most active during warm wet/humid weather (especially where nights are warm).  When the weather warms up again and the nights stay warm, you may want to consider a fungicide program for the damaging fungus.

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 have emerged.  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 significant in some areas, they are infesting outdoor ornamentals in many parts of the province (watch your Caragana, Ptelea, Acer) where forage crops are receiving their first cut.  I often get 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.

Look for a second generation of Euonymus scale crawlers in container production (soon in landscape/field production).  Crawlers are tiny and bright orange, you can see them without a hand lens.  Treat at peak egg hatch – about 7-10 days after hatch begins.  Try weekly applications of insecticidal soap and the summer rate of horticultural oil to smother newly hatched crawlers.

Lecanium scale (Parthenolecanium corni) crawlers have hatched.  Monitor deciduous trees (e.g. Quercus, Fraxinus) and look for small, rounded, dark brown bumps on the undersides of small twigs.  Pick off these adult female scales and look for tiny, white grains underneathe….those are the eggs.  Crawlers are fast-moving, white insects with 6 legs.  Treat at weekly intervals with the summer rate of Landscape Oil and insecticidal soap.  Population of scale insects on and landscape trees that have southwest exposure will be further advanced in their development (i.e. the eggs will hatch sooner than on other trees).

Cottony maple scale crawlers have hatched.  Adult females are just starting to lay their eggs in those cottony masses.  They are often found on silver maples that are under stress.  Despite their name, I’ve seen them on a broad range of woody plants.  Monitor for peak egg hatch before attempting pesticide applications.

Lily leaf beetle adults are active.  Monitor for red beetles with small black heads, feeding on foliage of Lilium spp (Asiatic lilies) and also Fritillaria.  Try picking off adults (drop them into a bucket of soapy water) to reduce populations this spring.  Also monitor for yellow/orange eggs on undersides of leaves and pick off these leaves and destroy before egg hatch.  This is usually more of a pest in the garden than in production.

Photo of adults: http://www.forestryimages.org/browse/detail.cfm?imgnum=9000004

Photos of eggs: http://www.forestryimages.org/browse/detail.cfm?imgnum=1445004

Photo of larvae: http://www.forestryimages.org/browse/detail.cfm?imgnum=1445005

You won’t have trouble finding aphids infesting herbaceous and woody nursery stock this time of year.  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.  Several insecticides will knock down aphids, some newer products include Endeavor and Tristar.  Some softer alternatives include insecticidal soap.

Two-spotted spider mites are infesting container grown ornamentals (woody and herbaceous) in the greenhouse and in outdoor production.  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 include: DynoMite, Vendex, Forbid and Kelthane.  TSSM on field grown nursery stock will be emerging in the next couple of weeks. TSSM overwinter as adults on the ground, in polyhouses and in greenhouses.  After they emerge and lay their first clutch of eggs, try applying Apollo (an ovicide) at the FIRST sign of egg hatch.  This will help reduce viability of eggs and newly hatched motiles.  Do not make more than one application of Apollo per season.

Peachtree borer adults may still be 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 from the last generation.  The clearwing moths that emerge are very much attracted to sticky wing traps that are baited with peachtree borer pheromones. Place pheromone traps out in early-mid June (approximately 390 GDD Base 10^oC, ‘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 adults are likely finished flying (container production mainly).  To purchase pheromones, try ordering from IPM suppliers such as www.greatlakesipm.com and www.naturalinsectcontrol.com.

Maple petiole borer damage has become visible.  The larval stage of the insect (sawfly) bores a tunnel in the petiole, causing it to break off in the wind.  Fallen leaves are wilted and have a black discolouration on the petiole where it is shriveled (http://www.ppdl.org/dd/id/maple_petiole_borer-maple.html).  (It’s easy to mistake the black leaf petiole as a disease.)  The remaining segment of the petiole stays attached to the twig and usually contains the larvae of the borer.  This is why raking up and destroying fallen leaves does not help control the pest.  If you have some time on your hands, remove the stub of leaf petioles from the tree (these house the larvae) and destroy them.  The number of fallen leaves is not usually significant enough to have an effect on tree health.  Watering and light fertilizing may help the tree overcome foliar losses during long, hot, dry periods.  Check out the Michigan State U Landscape Alert website for excellent photos and more information: http://www.ipm.msu.edu/CAT01_land/L05-25-01MaplePetiole.htm

Birch leafminer larvae are quite active. Inspect expanding foliage for small, brown blotches or mines THAT START FROM THE LEAF EDGE.  Hold the leaf up to the light and look for frass and the small larvae inside the brown blotch.  Birch case bearer is also quite active right now but they cause much smaller leaf mines that usually are found in the centre of the leaf (with a papery case hanging down).  Where infestations are heavy, treat foliage with Orthene (or Cygon in the nursery) to help reduce populations of young larvae in the leaves.   

Bronze birch borer adults are still flying.  Birches with a history of bronze birch borer infestation may be visible at this time.  Symptoms appear as branch tip death, branch death and death of the leader and progresses quite quickly.  Natural resistance to this pest can be enhanced through activities that improve plant health, such as fertilizing (May, October), irrigating and removing any weeds and grasses that provide competition for the tree.  Betula pendula is most susceptible to this pest and should be avoided in areas of known BBB infestation.  Betula nigra and its selections have been shown to be quite tolerant to BBB attack.

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.

Where sucking insect pests were a problem in the past, monitor for honeylocust plant bugs and leafhoppers.  These populations are quite established and we are starting to see all life stages present; which makes management quite difficult.  To monitor, tap leaves over a white sheet of paper and look for small, yellowish-green insects.  Application of contact insecticides at this time will be much less effective then if used earlier in the spring when the nymphs were present.

Gypsy moth larvae are still feeding on foliage although they can be found hiding in bark crevices and under branches during the day. Larvae are dark, hairy caterpillars with red and blue spots on their back. They can be found on several different kinds of deciduous trees (and also on the undersides of branches on Colorado spruce).  Early larval damage looks like holes in the foliage, but later, foliage becomes completely stripped.  We are at the end of the widow for Bt (Dipel, Foray) to be effective.  For larger larvae, try Success (spinosad), it is a lower toxicity alternative to acephate, and carbaryl.  Apply insectidices to both leaf surfaces where possible (larvae are still feeding on leaf undersides now).  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 (this behaviour is peaking right now).  Homeowners will need to inspect burlap skirts and underlying bark crevices daily (1-3 pm is best) and remove/destroy larvae.  In early July, sticky bands around trunks (above pupation sites where possible) will help prevent adult females from laying eggs above those bands, and will attract males to the sticky surface.

According to the University of Maryland, the Emerald Ash Borer adults start to fly when the black locust (Robinia pseudoacacia) is blooming.  In Ontario, TREEAZIN is registered for use as an injectable insecticide (using the Eco-Ject system, BioForest Technologies) to help protect ash trees against Emerald ash borer attack.  Treat trees in July and August, on sunny days; this will facilitate rapid uptake and help protect the tree from larval attack.

Viburnum leaf beetle adults have emerged.  They too will feed on the interveinal tissue of leaves, causing skeletonising of the second flush.

VARIOUS HOSTS:

Black vine weevil adults have emerged 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), wait until the next generation of larvae in August or September and treat with Heterohabditis bacteriophora (BGreen) or Heterohabditis megidis (NemasysH) then.  This should result in a significant reduction of populations in late summer.

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 but control may not be acceptable.

EVERGREENS:

Keep protecting new foliage of evergreens for foliar blights.  Monitor for needlecast and blight diseases in the area.  Diplodia tip blight on 2 and 3 needled pines and Rhizosphaera needlecast 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.  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 out slightly, during sporulation.  New, soft growth is susceptible to foliar diseases until foliage hardens off.  Where there is a history of damage, treat with registered fungicides (copper oxychloride, Daconil) as buds start to open and protect new foliage until it hardens off.  Apply fungicides prior to precipitation events (spore dispersal).

If you are bringing in SOD (Sudden Oak Death, Phytophthora ramorum) host nursery stock from high risk areas, you may want to monitor for SOD symptoms.  Camellia, Rhododendron, Viburnum, Pieris, Kalmia and Syringa are considered to be high risk host genera, as they are most common genera found positive for SOD in retail and wholesale nurseries.  For a complete list of SOD regulated hosts, check out:        http://www.inspection.gc.ca/english/plaveg/protect/dir/sodspe.shtml

The California Oak Mortality Taskforce (COMTF) is a great place to find photographs and the latest info on this disease:    http://www.suddenoakdeath.org/

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 will be emerging soon and 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).

Cedar leaf miner adults are flying, look for tiny, grey-white moths hovering around foliage.  Tear along the margin of green and brown tissue and check for hollowed out tissue, larvae, pupae or and tiny emergence holes from the adult.  Emergence is staggered because there are more than one species of CLM here in Ontario.  Foliar applications of systemic insecticides are much more effective when applied to young larvae (August).  If no larvae can be found and interior tissue seems to be intact, CLM is not likely the cause of foliar damage.

Pine false webworm larvae have dropped to the ground and preparing for their long pupation period in the soil.  They are no longer susceptible to chemical control and they will do no more damage to their host.

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.  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.

Where Fletcher scale was a problem on evergreens last year, monitor for small, brown scale adults on evergreens such as Taxus, Thuja. These scales can be found on the undersides of foliage and twigs.  They have completed their life cycle and if you pick them off, you will see the tiny white eggs underneath.  You will also notice sticky honeydew and black sooty mould.  Fletcher scale CRAWLERS have hatched and are susceptible to many pesticides (including summer rate of horticultural oils).  Egg hatch is staggered so apply insecticides weekly and repeat to get optimal control.

Emerald ash borer has been detected in Quebec.  http://www.inspection.gc.ca/english/corpaffr/newcom/2008/20080626e.shtml

If you see large, black, long-horned beetles flying around, don’t be too alarmed.  White-spotted sawyer beetle adults have emerged and can be found in many areas, especially where there is firewood or dead trees (their favourite food).  They look a lot like Asian Long Horned Beetle but the native White-spotted sawyer has a distinctive white spot on the back of it’s “neck”.  Check out these photos:  http://imfc.cfl.scf.rncan.gc.ca/ins-images-eng.asp?geID=900

THIS MESSAGE WILL BE UPDATED Friday, July 11th.

– See more at: https://lawnsavers.com/nursery-and-landscape-report-2008/nursery-and-landscape-report-for-july-4-2008.html#sthash.tC6U3ziQ.dpuf