Environment Canada is calling for CLEAR SKIES TONIGHT. THERE IS A CHANCE OF FROST IN MANY AREAS (esp. north of the 401, East of Toronto). We can expect high’s in the mid-teens on Saturday and winds out of the SE at 20 km/hr. There is a chance of rain on Saturday evening and rain will continue through Sunday, when it will be cooler.
It will be no surprise to you that we are ~2 weeks ahead in Growing Degree Days from where we were last year. Growing Degree Day accumulations to the end of Thursday, April 22 (GDD 10oC / GDD 50oF).These numbers are only a guide for monitoring purposes. The temperatures at your production facility can vary significantly from the nearest weather station. Check out:https://climate.weather.gc.ca/?url=http%3A%2F%2Fclimate.weather.gc.ca
| Peterborough: 26.5 / 48 | Hamilton RBG: 43.5 / 78 | |
| Vineland Stn: 24.6 / 44 | London CS: 43 / 77 | Windsor: 70 / 126 |
NEW! Web-based TOOLS FOR HORT. Weed ID: http://www.weedinfo.ca/home.php Check out this website to help you identify weeds. You can type in the name of a weed or you can search through their weed index. If you’re still stuck, you can submit an electronic image and they will try to identify it for you (“Weed ID Services”).
PLEASE NOTE: 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. There is exception from the ban for the use of pesticides to maintain the health of TREES, if certain conditions are met. For more info, you can go to the Ministry of the Environment’s website athttp://www.ene.gov.on.ca/en/land/pesticides/index.php
VARIOUS ORNAMENTALS:
Given the amount of new growth out there and the fact that this is only April, yes, we should all be watching the weather closely and preparing plants for protection against freezing. Historically, frequent, low volume overhead irrigation (e.g. small droplet size nozzles designed for frost protection) throughout the coldest hours of the night/morning have been used to reduce freezing injury on new plant tissue. This takes repeated irrigation events, before temps go down to freezing, to keep a film of water on the plants (and under the ice). Water can also be used in early morning to melt ice more quickly and take that stress load off the plant tissue. Insulating cloths (light duty thermal blankets) have also been used quite successfully when secured around plants to hold heat around them during cold temperature events (sometimes in conjunction with irrigation). Fans can also be used to blow cold air off of plants, leaving a void for warmer air to come in (e.g. frost fans in vineyards, polyhouses).
Low temperature injury is quite common on new growth of evergreen Euonymus in the spring, even if air temperatures don’t fall all the way down below 0oC. The new growth of broadleaf evergreens is 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, covering 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.
Winter desiccation is evident on many evergreens this spring. Drying winds and lots of 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 (or potted) evergreens are even more susceptible because of their reduced root systems and ability to store water. Quite often, the most 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: Acrobat, Chipco Aliette WG and Subdue Maxx. For a complete list of SOD regulated hosts, check out: http://www.inspection.gc.ca/english/plaveg/protect/dir/sodspe.shtml
Monitor for black vine weevil larvae in the FIELD and LANDSCAPE on Rhododendron, Taxus, Thuja and Euonymus. 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 couple of 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).
Where black vine weevil larvae are a problem in CONTAINER PRODUCTION (e.g. perennials, evergreens), treat with Heterohabditis bacteriophora. This should result in a significant reduction of the population in just 1-2 weeks (grubs turn orange-pink). Check the viability (movement) of nematode stock solutions under the dissecting or compound microscope, you should even see movement with your hand lens. Black vine weevil larvae were starting to PUPATE in container production last week.
DECIDUOUS WOODY AND HERBACEOUS PERENNIALS:
Those of you growing stone fruit trees and chokecherry are probably dealing with some level of black knot. Cultural management (PRUNING) is the backbone of any black knot management program.
Although it may not be visible, there are cankers developing for next spring’s infection period so you need to prune infected branches well before the visible canker. It is VERY important to prune out infected branches during dry weather, BEFORE the trees bloom. Scout for Prunus species in hedgerows and neighbouring properties, prune out black knot, collect and destroy It is VERY important to COLLECT those pruned knots and DESTROY them (e.g. burning, burying and composting) IMMEDIATELY since clipped knots will still produce spores that infect new growth. In the nursery/orchard, Daconil has been shown to be the most effective fungicide. Fungicides need to be applied ahead of precipitation events during bloom and stem elongation. (Fruit-bearing mature Prunus: Daconil cannot be applied after shuck split or fruit will be injured)
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 will also help protect new shoots from fire blightinfections during warm, wet weather this spring.
Monitor ornamental Corylus sp. for signs of Filbert Blight, DORMANCY IS THE TIME TO PRUNE THEM OUT. Do not prune once new growth is emerging. 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. 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.
Applications of horticultural oil should be finishing up (daily temperatures between 4oC and 12oC are ideal). Timing of dormant oil applications are critical since freezing temperatures, mixing with sulphurand 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 galladelgids, 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, Euonymus scale, golden oak scale, fruit Lecanium scale and juniper scale.
Elm flea weevil adults may be noticeable on Siberian elm (Ulmus pumila) at this time. They emerge as the leaves are opening and start to feed. Early adult feeding causes small, discrete holes in the leaves. Adults are tiny, reddish brown weevils. They lay their eggs into leaf tissue and the larval stage feed as leafminers in spring and early summer. If you are seeing this pest, please let me know.
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 2010 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. These adults will be emerging as the buds start to swell and break. Adults will be laying eggson buds in early spring (reddish eggs on buds and new leaves). Research in Oregon suggests that horticultural oil applications (summer rate) targeting the first couple of egg clutches can help reduce the incidence of pod gall midge.
Egg masses of Eastern tent caterpillar have hatched. You can still prune them out where they are small (larvae often hide in tents during the day) and destroy them. Applications of B.t. (Dipel) on foliage during the evening hours is a good biological management tool for this pest.
Gypsy moth egg masses can be scraped off and destroyed at this time. 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 (Cercis canadensis blooming), 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.
Viburnum leaf beetle egg masses can still be pruned out and destroyed at this time in the field and landscape, but they are JUST ABOUT TO HATCH. Look for raised bumps on the undersides of 1 and 2-year-old twigs. The bumpy caps can be picked off to reveal the tiny, yellow eggs underneath. Monitor these eggs as they will hatching into larvae as 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 doing insecticidal applications.
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.
The regulated areas for Emerald Ash Borer have been updated. Check out:http://www.inspection.gc.ca/english/plaveg/pestrava/agrpla/survenqe.shtml
EVERGREENS & CONIFERS:
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.
Overwintering pine weevil adults have emerged from leaf litter and are mating on young twigs of pine and spruce where the Forsythia are blooming. 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). Pineroot collar weevils also overwinter as adults (developmental stages are overlapping), but they feed and lay their eggs at the root collar.
Euopean pine sawfly larvae will be just starting to hatch soon (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 can be easily destroyed or manually removed this early. 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 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 week or two, where temperatures permit and plant species are not sensitive. THEY ARE JUST ABOUT TO HATCH (Magnolia soulangiana, Amelanchier laevis, Pyrus calleryena ‘Bradford’ begin bloom)
Monitor for overwintering Balsam twig aphid eggs on terminal buds and the bark of fir, white spruce, Colorado spruce and juniper, they are susceptible to dormant oil applications. EGGS will be HATCHING VERY SOON and tiny, bluish great stem mothers (nymphs) can be found on 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
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.
Monitor overwintering, galls of cedar-apple rust and cedar-hawthorn rust and branch swellings ofpear-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
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 or 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 (winter desiccation may be suspect).
– See more at: https://lawnsavers.com/nursery-and-landscape-report-2010/nursery-and-landscape-report-for-april-23-2010.html#sthash.75zXDUe8.dpuf
