The LO Nursery Growers Summer Tour is coming up on Tuesday, July 14 . This year the group is visiting Sloans Nursery, Downham Nurseries, Heritage Country Gardens, Pieper Nurseries and Agrium Advanced Technologies. The cost for this a one-day tour is only $55.00 per person. Register with Kathleen Pugliese at Landscape Ontario (1-800-265-5656 ext. 309).
Environment Canada is calling for the chance of showers and possible thunderstorms this afternoon and tonight. Showers are expected for much of Saturday and Sunday is forecasted to be sunny and quite warm. Winds will be from the east this afternoon at 20km/hr and shifting to the north (20-30 km/hr) by Saturday evening. Saturday is the first day of the summer solstice!
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 10oC if you are working in oC. Subtract 50oF if you are working in oF. Only positive GDD’s are accumulated. Example: GDD 10oC = [(Max + Min)/2] – 10
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. For more information on the legislation call the Minitry of Environment information line at: 1-800-565-4923 or see the Ministry of the Environment’s website at http://www.ene.gov.on.ca/en/land/pesticides/index.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.
VARIOUS ORNAMENTALS:
Check for pupae and adults of black vine weevil on crops such as Rhododendron, Taxus, Thuja and Euonymus in field production nurseries and the landscape. Applications of beneficial nematodes are no longer effective at this time. The next window for nematodes to target the next generation larvae in soil will be September. In nursery production, Pounce and Thiodan are registered to manage the adult stages of weevils.
White grubs are pupating and many May/June beetle adults have already emerged. Preventative applications of Intercept (imidacloprid) are registered for white grubs in nursery production. The application period is late June and July (to coincide with egg-laying). Nematode applications for white grubs 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:
Where foliage on outdoor grown ornamentals appears chlorotic (yellow), cold temperatures we experienced a couple of weeks ago may be the culprit. I received a few calls from growers wondering about yellow foliage. It is likely not a fertilizer issue, but a result of that cooler weather. Plants should be greening up with these warmer temperatures.
Anthracnose and low temperature injury is still quite noticeable on several types of deciduous woody shrubs and trees (e.g. Fraxinus, Quercus, Acer etc.). Look for brownish black leaf margins and lesions, and distorted leaves. The next flush of growth should mask this symptomatic foliage.
Powdery mildew is becoming evident on highly susceptible ornamentals (Amelanchier, Rosa, Syringa) right now. Look for powdery, while residue on the tops of leaves as a symptom of this disease. Powdery mildew can lead to chlorotic, stunted foliage that may drop prematurely. Sulphur and copper are exempt for use as fungicides in the landscape. In the nursery, effective fungicides include Banner MAXX, Compass, Nova, MilStop, Rhapsody (B. subtilis) etc.
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).
We’ve noticed quite a significant population of aphids in the landscape and on outdoor nursery stock this year. There are several species that can be found feeding on the stems and leaves of woody and herbaceous plants. There is a species of aphid (black with white lines on the back) that we are finding widely across southern Ontario, it has been detected on several species of woody deciduous shrubs and trees. Insecticidal soap may help reduce populations of aphid, repeat applications at least weekly to give good knockdown. In the nursery, several insecticides are registered to manage aphids on ornamental crops.
Leaf galls such as bladder gall and spindle gall are quite common on maples, basswood and many other deciduous trees this spring. Worry not! The galls do not negatively impact tree health, leaves remain photosynthetic and do not usually drop prematurely from the tree. Treatment is not possible and it is not necessary.
Wooly beech aphid can be found feeding on the leaf undersides of ornamental beech trees this time of year. These adelgids can be found underneath the white, waxy material that protects them from pesticide applications. Worry not! Wooly beech aphid rarely affects tree health, it is just unsightly.
Have you noticed leaves wilting and dropping off sugar maples this year? Look closely and you will see that the leaf petioles (stems) are pinched and will be turning black in the next couple of weeks, as leaves break off in the wind and litter the ground below. This is typical injury of maple petiole borer, a sawfly whose larvae mine the petioles of sugar maple leaves. Maple petiole borer sawfly remain in the petiole stem that remains on the tree where they will complete their life cycle. Raking and destroying leaves will not reduce populations. Damage rarely has major negative consequences on tree health.
The honeylocust plant bug has taken it’s toll on honeylocust foliage this year. Their feeding causes twisting, mottled and defoliated stems. You will find nymphs and adults of this tiny green insects infesting honeylocust right now. Honeylocust leafhoppers will also become more numerous as the season progresses. Time insecticide applications (e.g. Tristar for leafhoppers) where monitoring reveals significant populations and injury. http://oregonstate.edu/dept/nurspest/honeylocust_plant_bug.htm
Oystershell scale (Lapidosaphes ulmi) crawlers have hatched. Adult scales look like miniature sea shells, often twisted to one side. They are small scale insects, about 3mm long when mature. They feed on the twigs of Fraxinus, Acer, Quercus, Malus and Tilia. Crawlers begin to hatch when the Philadelphus begins to bloom and the Syringa patula ‘Miss Kim’ are in full bloom. Treat crawlers at PEAK egg hatch, about 7-10 days after crawlers start to hatch. Try Landscape Oil and insecticidal soap first. Repeated applications will be required since crawler hatch is staggered.
Fall Cankerworm larvae (and other loopers) may still be feeding on deciduous tree leaves. Look for green or dark grey “loopers” or “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) when they are small. Spinosad (Success) insecticides may be effective once larvae reach a larger size.
Gypsy moth (Lymantria dispar)larvae can be found feeding on several different kinds of plants right now. The small, dark, fuzzy larvae are especially fond of Quercus, Tilia and Ulmus. With a hand lens, you will be able to see the blue and red dots on their backs. Dipel is not as effective with these larger larvae, especially after the head capsule turns yellow. Try spinosad (Success) insecticide to manage more mature lavae. 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. Homeowners will need to inspect burlap skirts and underlying bark crevices daily (1-3 pm is best) and remove/destroy larvae.
Peach tree borer (Synanthedon exitosa) adults are 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 are also starting to emerge in container production at this time. To purchase pheromones, try ordering from IPM suppliers such as www.greatlakesipm.com and www.naturalinsectcontrol.com.
Emerald ash borer adults are flying. TreeAzin (azadirachtin, neem) has an emergency use registration (until August 31) for emerald ash borer on ash. This is an injectable insecticide that is delivered though BioForest’s Ecoject system, to inject insecticides to protect ash trees from this borer. For more information contact BioForest (http://www.bioforest.ca/). The regulated areas for Emerald Ash Borer have been updated (it has most recently been found in Welland). 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
Two-spotted spider mites (TSSM, Tetranychus urticae) are showing up on greenhouse grown ornamentals (woody and herbaceous). 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. 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:
There have been a lot of calls about the poor health of cedar hedges this spring. I am referring to older, established cedar hedges that seem to have taken a really hard hit this winter. The Pest Diagnostic Clinic is getting samples and detecting spruce spider mites, cedar leaf miner and sometimes a tip blight, Pestalotiopsis funerea (Pestalotiopsis is often considered a weak pathogen). Quite often these hedges are associated with compacted soils and frequent irrigation events. Keep foliage out of the line of irrigation sprinklers to reduce leaf wetness periods and therefore, reduce diseases. Frequent irrigations also stimulate root growth close to the surface of the soil and can make the tree more susceptible to extreme temperature (including winter injury) and drought conditions.
Where foliar browning is evident on evergreens (broadleaf and needle-leaved) in the spring, we shouldn’t always assume it is a disease issue. I’ve been to a number of operations where foliar desiccation has been evident on evergreens (Picea, Juniperus, Buxus etc.). Most of the symptomatic plants have a less developed root system than other non-symptomatic plants in the same block. Winter desiccation is more pronounced on plants with smaller root systems (i.e. smaller storage of water).
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.
Check your conifers for raucus weevils. We have seen Otiorhynchus raucus feeding on the new growth of spruce and buds of eastern white cedar over the last two spring seasons. Where populations are high, Pounce and Thiodan can help growers manage the adult stages of this weevil.
Small, yellowish, Juniper scale (Carulaspis juniperi) have hatched. They usually start to hatch when the Kolkwitzia amabalis (beauty bush) is in full bloom and the Catalpa speciosa is in early bloom. This scale insect in not susceptible to dormant horticultural oil applications in fall or spring so you need to target pesticide applications to the crawler stage or you will miss the opportunity to manage them. Try summer rates of horticultural oil (e.g. Landscape oil) and insecticidal soaps. Repeated applications over a 3-week period will be needed to target all hatching nymphs of this scale.
Monitor for Euonymus webworm (Yponomeuta cagnagella) larvae on euonymus. Look for a cluster of leaves held together by webs and tiny, yellowish caterpillars with dark heads. Prune out or squish small infestations, chemical control is not usually warranted but Dipel (B.t.) should help reduce populations.
Euonymus scale (Unaspis euonymi) crawlers are active in container grown Euonymus and in the field/landscape. The crawler stage (newly-hatched nymphs) are orange begin to hatched when the Spraea x vanhouttei is in full bloom (or when the Kolkwitzia amabalis are beginning bloom). A second generation will hatch about 6 weeks later. Treat at peak egg hatch – about 7-10 days after hatch begins. Try repeated, weekly applications of insecticidal soap and the summer rate of horticultural oil to smother newly hatched crawlers.
Pine spittlebug seems to be quite common on evergreens this spring. Try using a strong stream of water to dislodge these sucking insect pests to reduce populations. In the nursery, Malathion, Pyrate and Sevin are registered to help reduce this pest.
A Pine tortoise–like scale (species to be confirmed) was found on young jack pine trees this week. We found a significant population on the lower branches. You’ll notice reddish brownish “bumps” along the undersides of twigs and copius amounts of honeydew and black sooty mould. They are very difficult to knock down because they are nearing maturity. It is advised to flag infested trees and treat them in early July to target the newly hatched crawlers. You can also prune out severely infested twigs right now to prevent the next generation of scale.
White pine weevil larvae (Pissodes strobi) will be feeding from inside the shoots (terminals) on pine and spruce. Terminal shoots become flagged or crooked in late June and July. Prune out infested shoots and destroy them to prevent the successful emergence of the next generation.
European pine sawfly (Neodiprion sertifer) larvae are actively feeding on Scots, red and mugo pine. Look for green larvae with dark heads feeding on last year’s pine needles. 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. Larvae will also be munching away in container grown Pinus (check your mugo pines). Remove colonies of young larvae manually or spot treat with contact insecticides. Some lower toxicity choices include Pounce and Success 480 SC.
Pine false webworm (Acantholyda erythrocephala) may still be found flying and laying their eggs on needles of white pine When eggs hatch, young larvae snip off foliage and make webby nests near the trunk. The larvae clip off more needles and pull them into the webby nest where they feed on them. The larvae feed mainly on older growth and will only eat the current year’s growth when all else has been consumed. The new nests can be dislodged with a strong stream of water.
Spruce spider mites (Oligonychus ununguis) can be found feeding on new growth of conifers (Abies, Picea, Pinus, Thuja etc.). Time miticide applications for “peak” egg hatch in areas of high populations. Use lots of water and pressure, try to coat undersides of twigs and foliage. Kanemite, Floramite 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.
Balsam twig aphid (Mindarus abietinus)nymphs have hatched and can be found feeding on new growth of Abies, causing it to become twisted and chlorotic. This generation of nymphs is very difficult to manage with pesticides. Focus pest management efforts on “stem mothers” next year.
Taxus or Fletcher Scale (Parthenolecanium fletcheri) nymphs are maturing and starting to lay their eggs on foliage of Thuja and Taxus. Look for honeydew and small, brown bumps on foliage, pick off scale and examine the undersides. If the tissue underneath appear “fleshy”, they are still maturing. If the undersides are packed with tiny, white grains, they have laid their eggs. Applications of insecticides are most effective against crawlers (once those eggs have hatched) in a couple of weeks or so. Repeated applications will be necessary since egg hatch is staggered.
Cedar leaf miner (Argyresthia sp) larvae are pupating and tiny, grey adult moths can be found fluttering around foliage. Tear along the margin of green and brown tissue and check for the presence of larvae, pupae or hollowed out tissue with a tiny emergence hole (where adults would exit). If no larvae can be found and interior tissue seems to be intact, CLM is not likely the cause of foliar damage. Foliar applications of systemic insecticides are much more effective when applied to young larvae (August). A light sheering of foliage in late August will also help reduce the number of larvae that successfully overwinter.
– See more at: https://lawnsavers.com/nursery-and-landscape-report-2009/nursery-and-landscape-report-for-june-19-2009.html#sthash.S5gdOwLH.dpuf
