Environment Canada is calling for continued hot, humid weather and showers for the weekend and for the next several days (high’s 28-32oC).
Growing Degree Day accumulations to the end of Thursday, July 21 (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: 576 / 1037 | Oshawa: 600 / 1080 | Hamilton RBG: 651 / 1172 | |
| Vineland Stn: 716/ 1289 | London CS: 704/ 1267 | Windsor A: 837 / 1507 | |
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
HOLD the DATE! Thursday, September 15. Nursery Growers Annual Summer Tour. This year the group will be doing a local tour of horticultural operations east of Toronto. More details to follow.
Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape database is available online. Check out www.dkbdigitaldesigns.com/clm
Weed Identification ONLINE: http://www.weedinfo.ca/home.php
Yellowing and sudden leaf drop has been reported on deciduous trees in the landscape and also on some crops in the nursery (e.g. Euonymus). Some of the leaf drop is likely in response to extreme heat, humidity and those areas not receiving as much precipitation. In some cases, spring diseases such as anthracnose have been linked to the dropped leaves. It is a survival mechanism of the plant and in most cases, does not lead to dieback.
VARIOUS ORNAMENTALS:
Our Nursery Scout is reporting resurgence of the population of green peach aphid (Myzus persicae) on various woody and herbaceous perennials this week. Look for these small, green, pear-shaped, sucking insects feeding on the newest leaves and stems. 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.
Potato leafhoppers are feeding! Monitor for leafhoppers (such as potato leafhopper) on nursery crops such as Caragana, and Acer (platanoides, saccharum), especially after forage crops have been cut on neighbouring farms. Adult leafhoppers are winged, very mobile, tiny, pale yellow-green jumping insects that are easily disturbed when you approach infested foliage. It almost looks as though they are being flicked off of the foliage. The soft, succulent growth we had this year was especially susceptible. Leafhopper nymphs are active and appear as tiny, flightless, yellow-green insects that move sideways, very rapidly across the leaf. Leafhoppers (and aphids) suck plant sap from expanding foliage and cause foliage to wilt, become off-coloured and flecked. Potato leafhoppers are especially damaging because they cause foliage to become stunted and deformed, with brown-black margins (�hopper burn�). Leafhopper injury also appears as bronzing or stippling on more mature leaves. Monitor populations and treat with insecticides before damage becomes economically threatening. Leafhoppers are also attracted to yellow sticky cards, for monitoring. Registered insecticides include Tristar and Sevin XLR.
http://dkbdigitaldesigns.com/clm/species/empoasca_fabae
European chafer adults may still be mating and swarming but most have laid their eggs in the soil. Japanese beetle adults are actively skeltonizing leaves of Prunus, Tilia, Syringa and Ulmus etc. Sevind is registered for JB adults in nursery production. A preventative application of Intercept (imidacloprid) is registered for white grubs in nursery production. In the field, the application period is June to July (to coincide with egg-laying). To help qualify for the Japanese beetle certification program, an application of Intercept on container stock should be some time between mid-June to July. The cut-off period for Intercept applications to comply with the JB Certification program this year may be as early as July 31st. Nematode applications for white grubs (e.g. European chafer) are not effective at this time. Try timing nematode applications for late August/early September to catch early instar larvae.
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) and deciduous trees. These leaf diseases are more prevalent under late-day irrigation since foliage does not dry off before the evening, prolonging the leaf wetness period and 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. There are several different fungicides labelled for foliar diseases, including Daconil, Dithane, Copper, Nova, Banner Maxx, Pristine (watch phyto on Physocarpus, Euonymous) and Rhapsody (a biological).
Powdery mildew is prevalent on herbaceous perennials (e.g. Phlox, Rudbeckia) and some deciduous shrubs (Amelanchier, Physocarpus). There are several fungicides registered for powdery mildew (Serenade/Rhapsody, Nova, Banner, Compass) but they work best as preventative and will not cure a moderate-heavy infection. Also available this year for the home garden is the biological, Serenade Garden. This product is available as a ready-to-use home garden product. https://www.planetnatural.com/product/serenade-garden-disease-control/
Pear trellis rust (Gymnosporangium fuscum) has become evident on pear trees this year in the landscape. Look for bright orange lesions on the tops of pear leaves. It is too late to do anything about this disease, leaves were infected during warm, wet conditions in May (from infected Juniperus sabinae, the overwintering host). Lesions are very unsightly and sometimes lead to premature leaf drop. Lesions will produce cr�me-coloured structures on leaf undersides in September and send spores to the alternate Juniper host. Once the pear leaves drop in the autumn, the tree is no longer infected (the disease does not overwinter on the pear tree). Annual infection of pear depends on the alternate host, Juniper. Keep trees healthy and where possible, protect with fungicides during sporulation period of Juniper host in mid-spring. http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2007/23hrt07a2.htm
Where an additional flush of growth is emerging in container grown Euonymus fortunei, Euonymus anthracnose may be sporulating and infecting the new growth. Ensure good fungicide coverage before warm, humid nights. Daconil is registered for this disease. Anthracnose appears as a leaf spot (usually late summer) and stem canker and can be quite serious on variegated cultivars of Euonymus fortunei.
We are seeing dieback of Syringa reticulata ‘Ivory Silk’ in field production nurseries. Those trees growing on heavier, not-as-well draining soils with clay in them are holding too much water/insufficient aeration and the fine feeder roots of the trees are dying. In the canopy, we are seeing wilting, tissue browning, brown leaves persisting on the trees. If you slice into the cambium on the stem at the soil line, you will see brown lesions in the tissue. Previous lab reports have come back with Pythium root and stem wilt. The underlying cause is poorly-drained soils and ‘Ivory Silk’ intolerance of heavy soils.
Fall webworm larvae may be starting to feed on trees. We’ve seen them recently on Betula (birch) and Ribes (current), they are also common on Fraxinus (ash) and Juglans (esp. black walnut). Look for webbed tents on the ends of branches with fuzzy, cr�me-coloured caterpillars inside. The tents can be easily pruned out and destroyed (e.g. squished). Pruning out infested branches can be quite effective right now since there are multiple generations of this pest. Chemical pesticides may give some reduction in webworm populations but it is very difficult to get past that web. 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 in the landscape.
Are you seeing strange growths on the leaves of deciduous trees and shrubs? There are several different kinds of leaf galls on ornamental woody plants and the vast majority are completely benign in terms of plant health. I’ve had lots of questions about strange bumps (white, pink, red, green) on oak, ash maple leaves and velvety fuzz (red to orange) on various plants (including maple). Many of these leaf galls are inhabited by immature, tiny wasps, mites and midges. Take a good look at the leaf, if the tissue is still green and its attached to the tree; chances are the gall-forming insect isn’t detrimental to the tree. An exception to this rule are some oak twig galls (gouty, horned), which cause twig dieback.
Various species of aphids (e.g. green peach aphid, melon aphid, foxglove aphid) may still active on deciduous and broadleaf woody and herbaceous plants (spiraea, hosta) in the greenhouse, polyhouse and outdoor production. According to our nursery scout, the heat has enabled populations to explode. Because of the earlier cool weather, foliage is much 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.
The regulated areas for Emerald Ash Borer can be found at: http://www.inspection.gc.ca/english/plaveg/pestrava/agrpla/survenqe.shtml
Peach tree borer (Synanthedon exitosa) 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. The clearwing moths that emerge resemble wasps. Adults are very much attracted to sticky wing traps that are baited with peach tree borer pheromones. Place pheromone traps out in early-mid June (approximately 390 GDD Base 10oC, ‘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 have started to emerge in container production at this time. To purchase traps, try ordering from IPM suppliers such as www.greatlakesipm.com and www.naturalinsectcontrol.com.
Magnolia scale is quite common in the landscape this year. Right now, magnolia scale appears as large, white scales with a dusting of white powder. They will be starting to turn pinkish-orange and lay their eggs pretty soon. Pick off scale insect and look at the underside: if it is still fleshy, they haven’t matured yet. If tiny, white grains can be seen (like salt grains), they have started laying their eggs. Crawler hatch usually starts late July to early August (~1200 GDD 10oC). If you want to try insecticides against the crawler stage, make sure you are making at least 3 repeated applications, 7 days apart. This will have much better knockdown since crawler emergence is staggered. Insecticidal soap and the summer rate of horticultural oils should give good knock down. Malathion, Orthene and Sevin are registered for this pest in the nursery.
European fruit Lecanium scale crawlers are active. Look for adults: reddish brown bumps on the twigs of deciduous trees such as Quercus, Fraxinus and Acer. Crawlers are tiny, pale tan and emerge slowly over several days, multiple applications of insecticides may be warranted. For a low toxicity alternative, try insecticidal soap and the summer rate of horticultural oil where appropriate.
Two-spotted spider mites (TSSM) can be found on greenhouse and outdoor grown ornamentals (woody and herbaceous). This week our Nursery Scout found them feeding on Buddleia sp and Sambucus. 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 in the greenhouse include: DynoMite, Vendex, Shuttle, Floramite, Avid and Kelthane. Apollo is registered in outdoor nursery crops to knock down the egg stage and newly hatched nymphs. In the greenhouse, biocontrol agents should be brought in to coincide with the first sign of TSSM. Phytoseiulus persimilis is a predatory mite that feeds on TSSM when temperatures are below 26oC and it is a good choice when TSSM populations are low-moderate. Amblyseius californicus is a predatory mite that can be brought in ahead of TSSM appearance (because it can find other sources of food).
EVERGREENS:
Red-headed pine sawfly will soon be 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. Several contact insecticides are registered for conifer sawflies, try Success 480 SC as a low toxicity alternative.
Cedar leaf miner adults, the tiny silvery-white moths may still be fluttering around foliage in the southwest. Tear along the margin of green and brown tissue and check for the presence of tiny, brown pupa or just empty tissue (to confirm CLM is the cause of the browning foliage). Applications of systemic insecticides (to target larvae) are much more effective when applied to young larvae (early-mid 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).
White pine weevil larvae are white, legless larvae feeding and pupating inside the terminal of pine and spruce, causing them to wilt, flat and turn brown. Larvae will be pupating soon. Insecticide applications are futile at this point but do inspect white pine, Norway and Serbian spruce for wilting or hooking terminals. Prune out infested leaders and destroy them ASAP to reduce population of next generation adults.
Monitor for black vine weevil ADULTS in the FIELD and LANDSCAPE for Rhododendron, Taxus, Thuja and Euonymus. It’s too late for applications of nematodes in the field/landscape. Strawberry root weevil can also be a problem in field production of evergreens, adults have emerged. Signs of strawberry root weevil adults include brown, flagging shoot tips (and small girdling marks at the base of the flagged shoot) on Thuja (eastern white cedar). To scout for adult weevils, place a tarp or large piece of card board under the tree, shake branches vigorously and look for brown-black weevils �playing dead�. Insecticides for adult weevils in the nursery include Pounce, Sevin and Thiodan. Remember, adult weevils feed at night. Spray insecticides in late evening to target adults and reduce UV degradation (e.g. Pounce).
Black vine weevil adults are active in CONTAINER production. Where black vine weevil larvae are a problem in CONTAINER PRODUCTION (e.g. perennials, evergreens), insecticide applications can be made to target the adult stage. Nematode applications for larvae will have to wait for late summer/early autumn.
Taxus or Fletcher Scale crawlers are active on twigs and foliage of Thuja and Taxus. Look for tiny, white-clear crawlers on foliage (you will need a hand lens to see them). Since crawler hatch is staggered, two-three applications of insecticides during the crawler stage will give some good management of this pest.
Monitor for spruce spider mites on conifers with a history of mite damage. Newly hatched spruce spider mites are brown with a black back and very tiny with 6 legs (visible mainly with hand lens). Adults are a little larger, darker and have 8 legs. Monitor lower branches, this is where most of the feeding damage is done, on the morning sun side of the tree. Mite injury looks like bronzing (tiny, yellow flecks on the needle seen through hand lens). Miticide applications (e.g. Floramite, Kanemite, Vendex) are recommended where populations are at damaging levels.
– See more at: https://lawnsavers.com/nursery-and-landscape-report-2011/nursery-and-landscape-report-for-july-22-2011.html#sthash.dl1nCQzI.dpuf
