Environment Canada is calling for showers this morning and sunshine for many areas this afternoon. It will be sunny and much cooler on the weekend. Overnight low’s are expected to be above freezing in southern Ontario.
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 will be pupating soon. 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:
Two-spotted spider mites (TSSM) will be starting to show up on greenhouse grown ornamentals (woody and herbaceous) soon. 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).
For those of you hoping to protect Norway maples from tar spot this year, fungicide applications should be taking place before precipitation events, until leaves harden off. Fallen leaves from last year’s growth contain fruiting structures that are releasing infective spores during rain events, from now until middle of June (spore release has been good because of all the rain; sporulation should be finishing up earlier than usual).
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. Protect new growth before rain events with fungicides throughout leaf emergence (until leaves harden off). 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 blight infections during warm, wet weather this spring.
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.
All this rain has stimulated sporulation of cedar-apple rust and cedar-hawthorn rust and branch swellings of pear-trellis rust on Juniper. These slimy, orange projections contain the spores that will infect the alternate Rosaceous hosts: Malus, Crataegus, Amelanchier, Pyrus etc. Apply protectant fungicides (such as Nova) to Rosaceous hosts when the Juniper galls start to sporulate this spring. Keep Rosaceous and Juniper hosts separated from eachother where possible. For photos of galls: http://www.uoguelph.ca/~thsiang/rust/rust.htm
The elm flea weevil, (Orchestes alni) has been found most recently in Ohio, Michigan and Ontario landscapes. Siberian elms are especially susceptible to this pest. The adults feed on leaves and the larval stage is a leafminer. If you are seeing holes in elm leaves, look for TINY (2-3 mm long), brown weevils with black spots on their backs and a prominent snout. The larval stage (leafminer weevil, white with no legs) is starting to show symptoms in southern Ontario. (It is not to be confused with the elm leaf beetle, the ELB larvae feed openly on the surface of Siberian elm and the adults are much larger beetles OR the elm leafminer: a sawfly larva). http://www.ipm.msu.edu/cat08land/l05-09-08.htm#12
Where honeylocust plant bug was a problem last year, monitor for nymphs of this tiny green insects. They are quite prolific on street tree honeylocusts right now. Honeylocust leafhoppers will also become more numerous. Time insecticide applications (e.g. Tristar for leafhoppers) where monitoring reveals significant populations and injury. http://oregonstate.edu/dept/nurspest/honeylocust_plant_bug.htm
Birch trees with a history of bronze birch borer infestation should be pruned by now. Destroy pruned material to prevent emergence of beetles. Birch leaf miner larvae are starting to cause noticeable blotches in leaves. For nursery growers, Cygon is registered as a soil drench or foliar applications, Orthene is registered as a foliar application to reduce the incidence of birch leafminer in nursery production.
Eastern tent caterpillar larvae are quite widespread this year, webby tens can be seen on Prunus, Crataegus and Malus sp. all over southern Ontario. Dipel (B.t., Bacillus thuringiensis) can be effective against young larvae. 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 in the nursery.
Fall Cankerworm larvae are feeding on deciduous tree leaves throughout the south right now. Look for green or dark grey “loopers” 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 soon as possible.
Gypsy moth 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. For early instar larvae, some control can be achieved using Bacillus thuringienesis (Dipel, Foray), 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.
Viburnum leaf beetle larvae are starting to cause noticeable injury on Viburnum leaves The larvae were 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. Also watch for tiny, snowball aphids inside twisted up leaves of Viburnum. These aphids are difficult to manage with contact insecticides due to their protected feeding location, systemic insecticides may be required where populations are economically damaging.
Where defoliation is apparent on dogwood (Cornus sp.), check the undersides of the leaves for tiny, slug-like larvae. Larvae will also develop a white, waxy covering and become more noticeable. These larvae are dogwood sawflies and are not susceptible to Dipel (B.t.). They will be susceptible to other broad spectrum insecticides, such as Success 480 SC.
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 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.
Monitor for Euonymus webworm larvae on container grown Euonymus fortunei (it will be hatching in a couple weeks in the field). 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.
Newly hatched nymphs of pine bark adelgid are susceptible to chemical control until their white, waxy covering has developed (2nd nymphs at 32-340 GDD Base 10oC). Pesticide applications include (Malathion, Orthene, Tristar). 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.
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.
Pine tortoise 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.
Pine weevil adults (Hylobius and Pissodes spp.) have mated and laid their eggs. 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. White pine weevil larvae will be feeding from inside the shoots of terminals on pine and spruce and flaggin or Shephard’s crooking will become apparent in late June. Prune out infested shoots and destroy them to prevent the successful emergence of the next generation.
European pine sawfly 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 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 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 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 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 are feeding and producing copious amounts of honeydew. Focus pest management efforts on the next generation of crawlers in about 4 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, green-yellow 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 larvae are feeding and developing under bark of stressed or dead pine trees and stumps. Those larvae will develop 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-29-2009.html#sthash.Gw69qB3K.dpuf
