Spring is finally here! Environment Canada is calling for sunshine today and the risk of showers for Saturday. Daytime highs are expected to be in the “normal range” for this time of year, 14-19oC in many areas of southern Ontario. Night time lows will be 0-5oC (cooler to the north and east of Toronto).
Growing Degree Day summaries are not available at this time. If you would like to track GDD’s from the weather station nearest you, check out: http://climate.weatheroffice.ec.gc.ca/climateData/canada_e.html). Just record the maximum and minimum temperature for each 24 hour period, take the average and subtract off 10 if you are working in oC and subtract 50 if you are working in oF.
[GDD 10oC = (Max + Min)/2 – 10]. Only positive GDD’s are accumulated.
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. There are numerous ways to get more information on the legislation. You can go to the Ministry of the Environment’s website at http://www.ene.gov.on.ca/en/land/pesticides/index.php
This web site contains the Act and the Regulations, the new 11 pesticide classes the warning signs and notice signs. Fact sheets for each of the sectors that are impacted by this legislation are also listed under “What You Need To Know”. You can also telephone the Ministry of the Environment at 1-800-565-4923. This will get you to their Public Information Centre and you can dial 0 to speak to an Information Officer. They will direct you to a Regional Pesticide Information Officer. If you know the telephone number of your Regional MOE Office, you can telephone them directly and ask to speak to the Pesticide Information Officer. A list of all the regional offices and the 1-800 numbers are listed at: http://www.ene.gov.on.ca/en/contact/regionalmap.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, effective April 22, 2009.
VARIOUS ORNAMENTALS:
Winter desiccation is evident on many evergreens this spring. Drying winds and warm, sunny days in late winter caused foliage to lose water. Because the ground was still frozen, roots could not replenish lost water from the foliage and the foliage dried out and became brown. Newly-transplanted evergreens are even more susceptible because of their reduced root systems and ability to store water. Quite often, the damage is on the afternoon sun side of the plant. Take heart, as long as buds are not damaged, the emergence of new growth should hide most of the winter burn.
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. Fungicides registered for SOD in nurseries include: Subdue Maxx, Chipco Aliette WG. For a complete list of SOD regulated hosts, check out: http://www.inspection.gc.ca/english/plaveg/protect/dir/sodspe.shtml
Where nursery stock continues to be maintained in a polyhouse, caution should be taken when applying pest control sprays. Temperatures in the polyhouse can soar on clear sunny days, causing the chemical to injure foliage. Ventilation holes should be cut to keep high temperatures and high humidity at bay. High humidity has been linked to distortion and stunting of new growth on vines and shrubs and should be addressed where these symptoms have been observed. Fungal and bacterial blights (e.g. Pseudomonas blight on Syringa) of woody stock can often be attributed to stressful conditions experienced under poly and also the extreme shifts in environment once the poly is removed. Pseudomonas bacterial blight looks very similar to low temperature injury, and often the two conditions go hand-in-hand. In container nurseries, where Pseudomonas blight on lilac (and other deciduous shrubs) was a problem last season, you may want to consider an application of copper as buds start to swell. Research also indicates that the copper becomes more effective if combined with Dithane. The bacteria overwinter next to the buds and can infect leaf tissue once bud caps split open. Again, infection and spread of this bacterial disease can be reduced where temperatures and humidity levels are reduced (i.e. ventilation under poly) and new foliage is more gradually hardened off.
For growers forcing euonymus under in the poly or greenhouse to encourage a flush of growth on Euonymus with a history of anthracnose, consider protecting foliage with Daconil. (This will not be necessary where euonymus are growing unprotected.) Euonymus anthracnose appears as a leaf spot and canker on small twigs during periods of HIGH TEMPERATURE and high humidity/leaf wetness periods (which may be possible under poly in the spring). Infected leaves will drop and twig cankers and dieback can also be seen. Ventilate poly to keep stressful humidity and temperature levels down. The fungus overwinters on old leaves and twigs. Remove and destroy dead and dying twigs and leaves from infected plants to reduce further spread.
Low temperature injury is quite common on new growth of Euonymus in the spring, even if air temperatures don’t fall all the way down below 0oC. The new growth on broadleaf evergreens are especially sensitive to low temperature injury. Where broadleaf evergreens are putting out new growth in the field or in uncovered container beds, consider protecting new growth from low temperature injury (air temp 2-3oC and below). Methods of preventing low temperature injury include night time watering, copper applications and removing cold air masses through air circulation (fans). Low temperature injury damage foliage appears water soaked in the 24 hour period following the low temperature event. The damaged tissue will turn brown and often becomes susceptible to attack by weak fungal and bacterial pathogens (Pseudomonas bacteria, Colletotrichum anthracnose), giving a misdiagnosis of the original cause of the problem.
Check for overwintered larvae of black vine weevil on Rhododendron, Taxus, Thuja and Euonymus in the field and landscape. Where soils are cold and moist (e.g. landscape), you can try an application of nematodes (Steinernema kraussei, NemasysL) to help reduce the population of larvae in the next 6-8 weeks. Where black vine weevil larvae are a problem in CONTAINER PRODUCTION (e.g. perennials, evergreens), wait until soils reach 10-12oC and treat with Heterohabditis bacteriophora (e.g. BGreen) or Heterohabditis megidis (e.g. NemasysH). This should result in a significant reduction in populations in just two weeks. Since Heterohabditis species require moist, warm (10-12oC) soil, we find that they do not work well in the landscape/field unless ample, supplemental irrigation can be provided for the 2 weeks following application. NemaysL is therefore a much simpler solution for the landscape/field in the spring (apply when soils reach 5-7oC). Met 52 (Metarhizium anisopliae) is a new bioinsecticide for container grown ornamentals that has insecticidal properties against root weevils. Met 52 must be applied by mixing with moist potting media before or during potting up plant material.
Given how wet it was last summer and fall, it’s probably safe to say that we could be seeing a bit of a spike in white grubs this spring. Moist conditions would have had a positive effect on larval development last summer and would lead to increased populations of European chafer, May/June Beetle, Japanese Beetle and other species in the soil. Only preventative applications of pesticides are registered for white grubs in nursery production, and the application period is in June and July during the adult flight period. Nematode applications for white grubs are much more effective in late August/early September as they will target the 1st and 2nd instar. Later instars of white grubs do not seem to be as susceptible to nematodes.
DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:
Aphids are quite common in greenhouse grown herbaceous ornamentals this time of year. Green peach aphid is one of the most common species we saw this week although melon aphid and foxglove aphid are also quite common. Various insecticides are registered to manage aphids in greenhouses including Endeavor, Intercept and Enstar II. Where populations aren’t economically damaging, biological control (e.g. Aphidius, Aphidoletes) may provide excellent management when introduced on a regular basis. Some growers use “banker plants” (cereal plants harbouring aphid species that don’t feed on ornamentals) to keep a constant introduction of beneficial, parasitic wasps (Aphidius) into the crop while aphid populations are still low. These banker plants have been used successfully by many Ontario greenhouse growers. Biocontrol suppliers include Koppert, Plant Products and Canadian Hydrogardens.
Monitor ornamental Corylus sp. for signs of Filbert Blight, PRUNE OUT CANKERED STEMS WHERE PLANTS ARE STILL DORMANT. This is a fungal disease that causes rows of small, black, crescent-shaped cankers along dead stems. Corylus avellena ‘Contorta’ is particularly susceptible. Remove cankered shoots, 20-30 cm behind visible cankers, when plants are dormant. Pruning when new shoots are emerging will accelerate the spread of this disease. Spray fungicides to protect new growth, starting at bud swell to bud break. Registered fungicides for this disease include: Copper oxychloride 50, Copper Spray and Flint (Compass).
Brown shoots on juniper may be a symptom of juniper tip blight (Kabatina blight). A small grey band or pinched grey canker can be found at the base of the infected shoot, this is where the spores come from. Where plants are still DORMANT, PRUNE OUT DEAD SHOOTS during dry conditions (and remove shoots) to reduce disease spread. Disinfect pruning shears between each cut (e.g. rubbing alcohol, other sterilants) to reduce disease spread. Pruning is not suggested once new growth appears as it will help spread this disease. Where cankers are found, copper and Dithane are registered to protect emerging new growth this spring and summer.
Black knot is easy to see on Prunus sp. at this time. Monitor gardens and adjacent wild areas for Prunus shrubs and trees for large black knots on previous years twigs. If you have the time to prune, prune the cankers out quite close to the main stem BEFORE LEAVES EMERGE. Pruning too shallow retains the undetectable, developing canker on the tree and does nothing to limit the disease. Fungicides may give some suppressions when sprayed at green tip, pre-bloom and blossom time. Fungicides include Maestro. For more information:http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2003/03hrt03a4.htm
Monitor overwintering, galls of cedar-apple rust and cedar-hawthorn rust and branch swellings of pear-trellis rust on Juniper. Prune out galls where they are dormant and destroy. These juniper galls will begin producing slimy, orange projections during warm, wet/humid weather. These projections contain the spores that will infect the alternate Rosaceous hosts: Malus, Crataegus, Amelanchier, Pyrus etc. Keep Rosaceous and Juniper hosts separated from eachother where possible. Apply protectant fungicides (such as Nova) to Rosaceous hosts when the Juniper galls start to sporulate this spring. For photos of galls: http://www.uoguelph.ca/~thsiang/rust/rust.htm
Applications of horticultural oil should be carried out where plants are still dormant and temperature are mild (daily temperatures between 4oC and 12oC are ideal). Timing of dormant oil applications are critical since freezing temperatures, mixing with sulphur and applying at the dormant-rate on actively growing tissue may result in injury. Apply dormant oil on clear mornings to facilitate rapid drying. The oil provides a barrier that restricts both respiration and movement of overwintering insects. It is quite effective for the management of overwintering spruce gall adelgids, scales and mite eggs (including spruce spider mite, European red mite, maple spider mite on silver/red hybrids). Keep in mind that most of these insects overwinter on the undersides of leaves and twigs. Since the oil droplets come out of solution so easily, frequent agitation is VERY important during application. Some plants listed as sensitive to dormant oil applications include: Japanese maple, red maple, sugar maple, hickory, walnut, blue junipers, blue Colorado spruce, white pine, red oak, and to a lesser extent: yew and cedar.
The nymphs of many scale insects have overwintered on twigs and are visible at this time. Heavy infestations can be pruned out and destroyed where possible (or use horticultural oil). Some species of scale to monitor for include: Magnolia scale, Fletcher scale (Taxus, Thuja), Euonymus scale, golden oak scale and European fruit Lecanium scale (Quercus). Pine needle scale, Oystershell scale and Juniper scale overwinter as eggs below the dead females and are NOT susceptible to applications of horticultural oil at this time.
Remember the maple spider mite (Oligonychus aceris) injury you saw on the silver-red maple hybrids last year? The tiny, red, overwintering eggs of those maple spider mites can be found on the leaf scar, just below the bud for this years growth, on 2008 twigs. The mite eggs are tiny flat, red spheres and are just barely visible, you will need a hand lens to see them. Where populations caused damage last year, applications of horticultural oil prior to leaf emergence should help smother eggs and reduce the population.
Where honeylocust podgall midge was a problem in the past, monitor trees for overwintered adult midges soon. These adults will be emerging as the buds start to swell, a little later on. Adults will be laying eggs on buds in early spring (reddish eggs on buds and new leaves). Recent research in Oregon suggests that dormant oil applications targeting the first couple of egg clutches can help reduce the incidence of pod gall midge. This involves applications of product early in the season, starting before foliar emergence.
Birches with a history of bronze birch borer infestation should be pruned by now. Destroy pruned material to prevent emergence of beetles. 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.
Manually remove and destroy the egg masses of Eastern tent caterpillar where plants are still dormant. The egg masses appear as swollen, shiny grey bands around small twigs of cherry, crabapples and hawthorns. They actually glisten in the sunlight. Egg masses will be hatching when shoots start to emerge, usually when the Forsythia is in full bloom. Dipel (B.t., Bacillus thuringiensis) can be effective against young larvae once they are all hatched and are starting to feed on foliage. Spray B.t. on foliage during the evening hours as young larvae feed at night. B.t. does not have any contact insecticidal properties, larvae must ingest it (e.g. while feeding on foliage) in order to be killed. Other lower toxicity insecticides effective against young larvae include Success 480SC and Pounce. The larvae form tents in branch crotches and can cause severe defoliation where populations are high.
Gypsy moth egg masses can be scraped off and destroyed where they are still dormant. Typically Gypsy moth egg masses hatch where the Cercis canadensis and Viburnum carlesii are starting to bloom. The egg masses appear as raised, buff coloured fuzz on tree trunks, fence posts, buildings and other sheltered locations. When populations are high, you can find them on almost any overwintering object, even on leaf litter! When larvae begin to emerge, some control can be achieved using Bacillus thuringienesis (Dipel, Foray) and spinosad (Success) insecticide in the first 2 weeks after egg hatch. 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 usually peaks near the end of May). Homeowners will need to inspect burlap skirts and underlying bark crevices daily (1-3 pm is best) and remove/destroy larvae. Sticky bands around trunks will help prevent females from laying eggs above sticky bands and will attract males to the sticky surface. Extremely high populations of egg masses were noted in the Great Lakes region, including Toronto and Mississauga last year. Rainy weather last June helped spread diseases that kill GM larvae before they pupate, but there is still a residual population in many areas.
Viburnum leaf beetle egg masses can still be pruned out and destroyed where plants are still dormant. Look for raised bumps on the undersides of 1 and 2-year-old twigs. The bumpy caps can be picked off to reveal the yellow eggs underneath. Monitor these eggs as they will hatching into larvae as foliage emerges. The larvae are vulnerable to chemical control only during the first 7-10 days after hatch. Larvae feed on the interveinal tissue from the undersides of the leaves, keep that in mind if you are doing insecticidal applications. Repeated applications of softer alternatives (such as Class 11 insecticides) will be required to suppress populations of larvae.
The regulated areas for Emerald Ash Borer have been updated. 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
EVERGREENS:
Where the Cornelian cherry dogwood (Cornus mas) is not blooming yet, the overwintering nymphs of pine bark adelgid are susceptible to chemical control. Avoid horticultural oil applications on (white pine) foliage as it can cause discolouration, direct sprays to the bark. Nymphs will be laying eggs in the coming weeks and those young nymphs are susceptible to pesticide applications (Malathion, Orthene, Tristar) until their white, waxy covering has developed (2nd nymphs at 32-340 GDD Base 10oC). Insecticide applications should be applied early in the time frame since the woolly covering protects them in late spring. Naked and woolly nymphs can also be dislodged with a strong stream of water.
Overwintering pine weevil adults are emerging from leaf litter and mating on young twigs of pine in the next few weeks. Monitor for small black/brown snout beetles around the foliage. Where populations are high, an application of contact insecticide (e.g. carbaryl) on foliage may help reduce numbers. Common weevil pests include white pine weevil (1/4 inch long, two white spots on the back), northern pine weevil and pales weevil (1/2 inch long, brownish black). Pales weevil adults also cause shoot flagging on white pine (they girdle twigs in summer and fall). Pine root collar weevils also overwinter as adults (and larvae, developmental stages are overlapping), but they feed and lay their eggs at the root collar. Some informal research indicates the spraying terminals when Forsythia are in full bloom, will help reduce the number of white pine weevil larvae infesting terminals in the summer.
European pine sawfly eggs overwinter on needles. The eggs will be hatching when the Acer platanoides are in full bloom and the Magnolia x soulangiana are in mid-bloom. Young larvae feed in groups on old foliage, older larvae (June) are green with dark green and crème coloured lateral stripes and a black head. They feed on several species including Pinus strobus and P. sylvestris. Larvae will be hatching in container grown Pinus soon. Remove colonies of young larvae manually or spot treat with contact insecticides. Some lower toxicity choices include Pounce and Success 480 SC.
Cooley spruce gall adelgid and eastern spruce gall adelgid overwintering females appear as tiny (you’ll need a hand lens to see them), grey/blue fuzzy spots at the base of buds, on the undersides of twigs. They are just barely visible with the naked eye. Galls do not usually have much effect on plant growth but appear unsightly in summer when they turn brown. Where populations are high, the adelgids are susceptible to chemical control (or horticultural oil applications) when buds start to swell. Target pesticide applications to the undersides of shoot tips. Use wettable powder formulations on blue spruce to prevent foliar discolouration.
Monitor for eggs of spruce spider mite on conifers with a history of mite damage. Spruce spider mite eggs appear as very tiny, round, reddish-brown spheres that adhere to the UNDERSIDES of twigs and foliage this time of year. You will require a hand lens to see them clearly. Monitor lower branches, this is where most of the feeding damage is done. These eggs are susceptible to dormant oil applications in the next few weeks, where temperatures permit and plant species are not sensitive.
Monitor for overwintering Balsam twig aphid eggs on terminal buds on fir, white spruce, Colorado spruce and juniper, they are susceptible to dormant oil applications. Eggs are hatching now and stem mothers (nymphs) will be feeding. The tiny, bluish grey aphid stem mothers can be found on/near terminal buds. Apply Diazinon, Malathion and Tristar on warm days (55 to 78 GDD Base 10oC) to target these stem mothers (before the bud caps loosen off).
Photos: http://www.insectimages.org/browse/subimages.cfm?SUB=321 http://ctrees.cas.psu.edu/pdfs/PestsofTrueFir.pdf
Where larch casebearer was problem in the past, eggs will be hatching where the Magnolia soulangiana are in early bloom. Larvae feed within newly-emerged foliage, causing it to die and turn straw-like in colour. High populations can cause moderate-severe defoliation.
Taxus/Fletcher Scale nymphs have overwintered on foliage of Thuja and Taxus. Applications of insecticides may give some suppression of this pest but nymphs are more susceptible in mid-to-late summer of the previous year. Nymphs will be feeding and producing copious amounts of honeydew in the next 4-6 weeks.
Cedar leaf miner larvae have resumed feeding from the inside of leaf scales. Tear along the margin of green and brown tissue and check for the presence of tiny, yellow/green larvae with dark heads (to confirm CLM is the cause of the browning foliage). Prune out infested foliage and destroy clippings to keep larvae from developing into adults before the end of May. 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.
Where leaf cupping and distortion was a problem last year, look for tiny, orange eggs and newly-hatched nymphs of the boxwood psyllid. The eggs hatch as the new leaves begin to emerge. The nymphs also secrete a white, waxy substance that can be seen on new foliage and on the nymphs themselves. Treat with insecticides such as insecticidal soap, carbaryl to reduce populations of newly hatched nymphs when new growth appears. Carbaryl is toxic to honeybees so avoid carbaryl applications on plants that are blooming. Where boxwood leafminer was a problem last year, treat new growth with a systemic insecticide (dimethoate) to limit damage from new generation larvae.
Pine shoot beetle adults have emerged. Adults lay eggs underneath the bark of stressed or dead pine trees and stumps. Those larvae will develop later in April and May. Remove brood material (i.e. trap (sentinel) logs, snags, dead/dying trees) before new progeny adults emerge (210 GDD, Base 10oC) to comply with the CFIA. All brood material must be burned, chipped (less than 2cm diameter) or buried (30 cm deep) to comply with CFIA standards.
– See more at: https://lawnsavers.com/nursery-and-landscape-report-2009/nursery-and-landscape-report-for-may-1-2009.html#sthash.OFCvGXXC.dpuf
