Environment Canada is calling for mixed weather for the weekend. We can expect a bit of sun, cloud and showers with high’s in the range of 18-20oC (cooler near the lake). It will be warmer (26-28oC) in the southwest (Windsor). Winds are expected to be out of the southwest at 15-20 km/hr. More seasonably warm weather is expected for next Monday and Tuesday.
Growing Degree Day accumulations to the end of Thursday, May 26 (GDD 10oC / GDD 50oF). (Courtesy of Environment Canada). These numbers are only a guide for monitoring purposes. The temperatures at your production facility can vary significantly from the nearest weather station.
Borden: 82 / 148
Oshawa: 79 / 142
Hamilton RBG: 92 / 166
Vineland Stn: 71 / 128
London CS: 129 / 232
Windsor A: 130 / 234
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. www.ontario.ca/pesticides
NEW TOOLS FOR Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape database is now available online. Check out www.dkbdigitaldesigns.com/clm
Weed Identification ONLINE: http://www.weedinfo.ca/home.php
VARIOUS ORNAMENTALS
With all the cool, damp and cloudy weather, we’re seeing a lot of extra Disease and Physiological problems on ornamentals this year. There are a lot more disease issues (blights, blotches, leaf spots and anthracnoses) in the field and in the greenhouse and much of that is due to low light levels and high relative humidity. Protectant fungicides such as Daconil and Nova will help protect new shoots until they harden off in the hotter weather. In the greenhouse, vent crops more frequently and keep air circulation up until the sunny weather returns.
We’ve seen a lot more slug damage in the last week or so. Look for holes in leaves, especially near the base of the plant. Slugs feed at night and the travel through moist, dark places. They will crawl up the plant stem at night and chew on leaves, leaving small-medium irregular holes. Slugs will hide during the day. Culturally, a dry, rough soil surface will really help reduce slug navigation. Try mulching soils and container media surfaces with fresh, dry wood mulch. Some growers will use sawdust or bedding that dries quickly after irrigation. In nursery production, growers have access to Sluggo (ferric phosphide), a low toxicity bait that is safe for other insects and animals. And also Deadline (metaldehyde) is available but has a higher toxicity and use restrictions on the label.
Some 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 temperature 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 moderated (i.e. ventilation under poly) and new foliage is more gradually hardened off to outdoor conditions. Some growers will leave the poly on into late spring and vent heavily to reduce leaf wetness periods and protect new foliage from low temperature events.
These are prime conditions for apple scab and fireblight, especially where trees are in bloom! Where new growth is still emerging on Malus sp., the overwintering fruiting structures of apple scab on last year’s foliage may still be infecting new growth. Apple scab appears as a blotching along veins and also on fruit, it is often associated with early leaf drop. Where appropriate, protect new growth before rain events with fungicides throughout leaf emergence (until leaves harden off). The apple scab fungus grows best at temperatures between 16-24oC, a leaf wetness period is required for the spores to germinate and infect emerging leaves. Intervals between fungicide applications can be longer during dry weather. Some newer fungicides registered for apple scab include: Banner Maxx and Serenade Max (a biological). Early applications of copper fungicides (as well as Streptomycin) will also help protect new shoots from fire blight infections during warm, wet weather this spring.
In the LANDSCAPE and GARDEN, check for overwintered LARVAE of black vine weevil on Rhododendron, Taxus, Thuja, Euonymus etc. in the garden. Where soils are cold and moist you can try an application of nematodes (Steinernema kraussei, NemasysL) by early May to help reduce the population of weevil larvae.
DECIDUOUS WOODY AND HERBACEOUS PERENNIALS
Black knot is easy to see on Prunus sp. (cherry) at this time. Monitor gardens and adjacent wild areas for Prunus shrubs and trees for large, black growths along the twigs. The dried, black growths are dead fungal tissue. Outwards from the black knot, look for swollen twig tissue that is orange-brown with splitting bark. Look closely between split bark and you will see olive-green tissue. That green tissue turns into tiny black bumps when the fungus is sporulating. Black knot sporulates when new twigs emerge and will infect them. Black knot infections are nearly invisible for the first year after infection. 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
Dutch Trig is registered for Dutch Elm Disease on Ulmus americana species in Canada. This is a new registration (fall, 2009) that contains a biological organism that induces an immune response to help the tree fight off DED infections. Injections should be made on sunny days during leaf emergence to maximize uptake.
Various species of aphids (e.g. green peach aphid) are being detected on deciduous and broadleaf woody plants in the greenhouse, polyhouse and now outdoor production. Because of the cool weather, foliage is much more tender and aphid populations are thriving. Biocontrol organisms are available to help suppress aphid populations in protected crops (midge: Aphidoletes and wasp: Aphidius). Insecticides registered for aphids in nursery production include: Tristar, Endeavor. Insecticide applications can be very effective where even coverage can be achieved.
Leafrollers can be found feeding on several deciduous woody trees and shrubs. Look for leaves that are suspiciously stuck together, or rolled up and held together by webbing. You will see a yellow-green tiny caterpillar inside feeding. An evening application of B.t. (Bacillus thuringiensis) should give kill of leafrollers within 3-4 days. Success (spinosad) another low toxicity choice. Get them now before the populations totally explode. Soft growth is making it easy for leafrollers to do their thing this spring.
Woolly Beech Aphids can be found on the undersides of beech leaves at this time. Where aphids are still woolly, they are very susceptible to most pesticides, including insecticidal soap. Other choices include: Tristar, Trounce (malation, orthene, pyrate, thiodan).
Snowball Aphids can be found on various Viburnum opulus this spring. Look for curled up, distorted leaves that are thickened. Inside the curled up leaf you will finy tiny white cast skins, and perhaps the white, woolly aphids that are causing the injury. This is a spring feeding aphid and will complete its lifecycle soon. Most of the damage has already been done.
Viburnum leaf beetle larvae are feeding. They hatch as the foliage emerges (Viburnum carlesii in full bloom, Syringa vulgaris first bloom). 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 making insecticidal applications. Young larvae are most commonly found on the undersides of the newest leaves.
Adults of the imported willow leaf beetle (Plagioderaversicolora) were found on Salix discolor (Pussy Willow) in container production nursery this week. The beetles were feeding on the leaves, chewing conspicuous holes and notches into them. They are easily recognizable by their shiny, metallic black to bluish-green color. Adults overwinter in cracks within the bark on the host tree and start feeding in the spring. They will soon be laying yellow eggs on the underside of leaves, which will hatch 2 weeks after that. The larvae will feed on the interveinal tissue on the underside of the leaves and damage can be significant. The adults can be found feeding in field production and in the landscape in the coming weeks and it’s best to target adults before they start laying eggs. Low toxicity insecticides registered for this pest include Success 480 SC. Other insecticides include Malathion, Orthene and Sevin. Avoid Sevin application when Salix is in bloom.
Fall Cankerworm larvae are feeding on deciduous tree leaves (Tilia, Fagus, Quercus). Look for green or dark grey “inchworms” feeding on the undersides and edges of leaves. They will strip leaves similar to Gypsy moth larvae (and in fact, the two can often be found feeding on the same tree). Cankerworm larvae are susceptible to Bacillus thuringienesis (Dipel, Foray), spinosad (Success) insecticides, but you will need to make B.t. applications as early in larval development as possible.
We saw small, black, adult sawflies of birch leaf miner mating and laying eggs on the foliage of Betula spp. last week. Where possible, a summer application of Landscape Oil (horticultural oil at the summer rate) can help smother adult sawflies. Various insecticides are registered for this pest in the nursery.
Where honeylocust podgall midge was a problem in the past, monitor trees for overwintered adult midges. These adults will be emerging as the buds start to swell. Adults will be laying eggs on buds in early spring (reddish eggs on buds and new leaves). Recent research in Oregon suggests that horticultural 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.
Eastern tent caterpillar larvae are coming up to their heavy feeding period. Applications of B.t. (Dipel) should be taking place as soon as possible. Apply B.t. on foliage during the evening hours.
Gypsy moth larvae have hatched and are tiny, fuzzy, black caterpillars dispersing on threads to various other hosts before they settle to feed. When larvae begin to feed, 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.
EVERGREENS
Where new foliage is emerging on conifers, monitor for needlecast and blight diseases in the area. Diplodia tip blight on 2 and 3 needled pines and Rhizosphaera needlecast and Stigmina 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. Stigmina appears on green and chlorotic needles, but doesn’t always lead to needle drop. 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 during sporulation. New, soft growth is especially susceptible to foliar diseases, but infection may also take place later in the season (we don’t know). Where there is a history of damage, treat with registered fungicides (copper oxychloride, Daconil) as buds start to open and protect new foliage. Apply fungicides prior to precipitation events (spore dispersal). Unfortunately, most of these blights and needlecasts can be found sporulating for much of the year.
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. The galls on juniper are/will begin producing orange sporulating bodies during warm, wet/humid weather. These sporulating bodies 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.
Cedar-quince rust is sporulating on Juniperus scopulorm in container production. Monitor for the small, orange masses on older twigs. Remove infected twigs or treat susceptible alternate hosts where possible.
Brown shoots on juniper may be a symptom of juniper tip blight (Kabatina is the fungus most commonly found in S. Ontario samples). We saw some on Juniperus scopulorum last week. 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 in early fall. 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. Where cankers are found, copper and Dithane are registered to protect new growth in summer.
Volutella blight on boxwood has been detected on some propagative stock of boxwood. Symptoms include black tissue discolouration along stems, tiny orange cushion-like fruiting structures and tip dieback and browning. Although the disease is worse in propagation zones, it can also be found in field production in moderate amounts. Care should be taken to avoid introducing Volutella blight through cuttings from infected plants. Remember, Volutella is often associated with wounds, keep the mother plants protect with fungicides once any pruning or cuttings are taken in the spring.
European pine sawfly larvae are feeding on last year’s pine needles. Look for small, green-tan larvae with dark heads clustered against needles. Where they are still feeding in a tight cluster, they can be destroyed or manually removed. A low toxic pesticide choice is Success. Closely examine pine trees and shrubs such as Pinus sylvestris, Pinus mugo, Pinus nigra.
Look for small black and orange (males) or orange (females) sawflies mating and laying eggs on new growth of spruce as adult Yellow-headed spruce sawfly. The adults are quite active on new shoots of spruce. There are several insecticides registered including Dragnet, Dylox, Pounce and Success to target young larvae. Larvae are green with lighter longitudinal stripes, yellow-brown heads. This is a significant pest of spruce in York region and has caused significant damage to spruce trees. http://www.dkbdigitaldesigns.com/clm/species/pikonema_alaskensis
Spruce budworm (Choristoneura fumiferana) can be found on the new growth of spruce at this time. In spring, the early instar larvae feed on male flowers and may mine buds and needles. Older larvae feed on expanding shoots, destroying them before they can fully elongate. The small, green larvae were detected because of small patches of browned foliage that had tiny nests made of shoots wrapped together by silk. Larvae can cause defoliation and also browning of the needles. B.t. (Dipel) is an excellent biological insecticide for suppressing spruce budworm populations in mid-late spring.
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). In the landscape, prune out infested foliage (twig tips) ASAP. Collect and destroy clippings to keep larvae from developing into adults before the first week 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 (winter desiccation may be suspect).
Most white pine weevil adults have finished laying their eggs and those eggs will be hatching into larvae inside 2010 terminals. Insecticide applications are futile at this point but do inspect white pine, Norway and Serbian spruce for wilting or hooking terminals in the coming weeks. Prune out, destroy and train a new leader.
Pine shoot beetle adults have emerged. The tiny beetles take flight after 2-3 days where temperatures reach 10-12oC. 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.
European pine sawfly larvae will be just starting to hatch (where Acer platanoides are in late bloom, Pyrus calleryena ‘Bradford’ begin bloom). Look for tiny, green-tan larvae with dark heads clustered against needles (they really blend in against the foliage!). They can be easily destroyed or manually removed this when they are still small (~1 cm). A low toxic pesticide choice is Success. Closely examine pine trees and shrubs such as Pinus sylvestris, Pinus mugo, Pinus nigra.
Cooley spruce gall adelgid and eastern spruce gall adelgid overwintering females are laying their eggs (under white, woolly masses) and are no longer susceptible to pesticide applications. Galls do not usually have much effect on plant growth but appear unsightly in summer when they turn brown.
Monitor for overwintering Balsam twig aphid eggs are hatching on terminal buds on fir, white spruce, Colorado spruce and juniper, they are susceptible to dormant oil applications. Eggs will be hatching in the coming weeks and stem mothers (nymphs) will be developing later this month. The tiny, bluish grey aphid stem mothers can be found on terminal buds. Monitor for stem mothers and apply Diazinon, Malathion and Tristar on warm days NOW (55 to 78 GDD Base 10oC) to target these stem mothers (before the bud caps loosen off).
Taxus or Fletcher Scale nymphs are active on foliage of Thuja and Taxus. Applications of insecticides may give some suppression of this pest at this time (but nymphs were more susceptible in mid-to-late summer of last year). Nymphs are feeding and producing copious amounts of honeydew (sticky, sugary residue on needles below infestation).
Monitor for spruce spider mites on conifers with a history of mite damage. Newly hatched spruce spider mites are reddish and very tiny (visible mainly with hand lens). Monitor lower branches, this is where most of the feeding damage is done. Horticultural oil applications to target overwintering eggs should be finishing up now and miticide applications (e.g. Floramite, Kanemite, Vendex) should be ready to go for when mite eggs hatch in the coming weeks (Magnolia x soulangiana in full bloom).
– See more at: https://lawnsavers.com/nursery-and-landscape-report-2011/nursery-and-landscape-report-for-may-27-2011.html#sthash.l47Is3bg.dpuf
