Environment Canada is calling for rain and wind today as a warm front is bringing in some unsettled weather. It will be warm and sunny on Friday. Rain is expected for many parts of S. Ontario on Saturday. It will become considerably cooler on Sunday and Monday with sunshine and much cooler nights (there may be a chance of frost in some areas). Yep, it’s the long weekend in southern Ontario alright.
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. There are numerous ways to get more information on the legislation. You can go to 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:
Low temperature injury is quite common on new growth of Euonymus in the spring, even if air temperatures don’t fall all the way down below 0oC. The new growth on broadleaf evergreens is especially sensitive to low temperature injury. Methods of preventing low temperature injury include night time watering, copper applications and removing cold air masses through air circulation (fans). Low temperature injury damage foliage appears water soaked in the 24 hour period, turning brown or black after that. The damaged tissue will turn brown and often becomes susceptible to attack by weak fungal and bacterial pathogens (Pseudomonas bacteria, Colletotrichum fungi), giving a misdiagnosis of the original cause of the problem.
Euonymus anthracnose (Colletotrichum gloeosporioides) appears as a leaf spot and canker on small twigs during periods of HIGH TEMPERATURE and high humidity/leaf wetness periods (which may be possible under poly in the spring). For outdoor grown euonymus, protective fungicide sprays are more important for the second flush of growth, next month.
Check for overwintered larvae of black vine weevil on Rhododendron, Taxus, Thuja and Euonymus in the field and landscape. Applications of beneficial nematodes should be finishing up since larvae are pupating at this time.
Given how wet it was last summer and fall, it’s probably safe to say that we could be seeing a bit of a spike in white grubs this spring. Moist conditions would have had a positive effect on larval development last summer and would lead to increased populations of European chafer, May/June Beetle, Japanese Beetle and other species in the soil. 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:
Aphids are quite common in greenhouse grown herbaceous ornamentals this time of year. Green peach aphid is one of the most common species we saw this week although melon aphid and foxglove aphid are also quite common. Various insecticides are registered to manage aphids in greenhouses including Endeavor, Intercept and Enstar II. Where populations aren’t economically damaging, biological control (e.g. Aphidius, Aphidoletes) may provide excellent management when introduced on a regular basis.
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 will be releasing infective spores after rain events, from now until the end of June (spore release depends on rain). Tar spot has begun sporulating at the U of Guelph research site in Guelph.
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). 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 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.
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. 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
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. It can cause significant defoliation on elm leaves so treat for adults (leaf undersides) now to reduce populations and help prevent egg-laying in leaves. Let me know if you see this weevil. (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). http://www.ipm.msu.edu/cat08land/l05-09-08.htm#12
Applications of horticultural oil should be finishing up. It is quite effective for the management of overwintering spruce gall adelgids, scales and mite eggs (including spruce spider mite, European red mite, maple spider mite on silver/red hybrids).
Where honeylocust podgall midge was a problem in the past, monitor trees for overwintered adult midges soon. 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 dormant 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. Where honeylocust plant bug was a problem last year, nymphs of this tiny green insect will be emerging soon (120 GDD 10oC). They start to feed early, on emerging leaves. Time insecticide applications (e.g. Tristar) where monitoring reveals significant nymphs leafhoppers. You will need a hand lens to monitor for these pests. 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. Branch and trunk applications of Pyrate may help reduce successful infestations of the next generation of larvae in nursery production if it is applied soon. Birch leaf miner adults (small, black sawflies) will be emerging soon to lay their eggs in leaf tissue. 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.
Egg masses of Eastern tent caterpillar have hatched since shoots have started to emerge, and the Forsythia is in full bloom. Dipel (B.t., Bacillus thuringiensis) can be effective against young larvae once they are all hatched and are starting to feed on foliage. 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. The larvae form tents in branch crotches and can cause severe defoliation where populations are high.
Gypsy moth egg masses are just starting to hatch, they can be scraped off and destroyed where they are still dormant. Typically Gypsy moth egg masses hatch where the Cercis canadensis and Viburnum carlesii are starting to bloom. When larvae begin to emerge, 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. Extremely high populations of egg masses were noted in the Great Lakes region, including Toronto and Mississauga last year. Rainy weather last June helped spread diseases that kill GM larvae before they pupate, but there is still a residual population in many areas.
Viburnum leaf beetle larvae are very tiny and feeding on the underside of emerging leaves, causing small holes. 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. Repeated applications of softer alternatives (such as Class 11 insecticides) will be required to suppress populations of larvae.
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 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 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. 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 susceptible to foliar diseases until foliage hardens off. Where there is a history of damage, treat with registered fungicides (copper oxychloride, Daconil) as buds start to open and protect new foliage until it hardens off. Apply fungicides prior to precipitation events (spore dispersal).
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.
Overwintering pine weevil adults (Hylobius and Pissodes spp.) have emerged from leaf litter and mating on young twigs of pine and spruce. Monitor for small black/brown snout beetles around the foliage. You can also find them clinging to the undersides of your pine trap logs (from Pine Shoot Beetle program). 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). 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. Some informal research indicates the spraying terminals when Forsythia are in full bloom, will help reduce the number of white pine weevil larvae infesting terminals in the summer.
European pine sawfly eggs overwinter on needles. The eggs will be hatching when the Acer platanoides are in full bloom and the Magnolia x soulangiana are in mid-bloom. 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. They feed on several species including Pinus strobus and P. sylvestris. Larvae will be hatching in container grown Pinus soon. 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 adults can be found flying around white pine foliage at this time. Adult sawflies are black, females have an orange head and males have a yellow face. They will be laying their eggs along the length of individual needles. 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.
Cooley spruce gall adelgid and eastern spruce gall adelgid overwintering females are starting to lay tiny, black eggs under those fuzzy, white masses. Adelgids appear as tiny (you’ll need a hand lens to see them), grey/blue fuzzy spots at the base of buds, on the undersides of twigs. The eggs are not susceptible to pesticide applications. Eggs will hatch as the new growth starts to emerge from the buds, nymphs will migrate to emerging shoots and will cause galls to form. Galls do not usually have much effect on plant growth but appear unsightly in summer when they turn brown. Where females haven’t laid eggs yet, the adelgids are susceptible to chemical control (or horticultural oil applications) when buds start to swell. Target pesticide applications to the undersides of shoot tips. Use wettable powder formulations on blue spruce to prevent foliar discolouration. The next opportunity for pesticide applications will be next fall.
Spruce spider mite eggs are just starting to hatch on conifers (Abies, Picea, Pinus, Thuja etc.) in southern areas. Spruce spider mite eggs appear as very tiny, round, reddish-brown spheres that adhere to the UNDERSIDES of twigs, foliage and bud scales this time of year. Newly-hatched mites (“motiles”) are reddish brown with black backs. You will require a hand lens to see them better. Monitor the undersides of twigs and look for clusters of eggs on the undersides of buds. The unhatched eggs are susceptible to dormant oil applications. Eggs will be hatching when the Pyrus calleryana ‘Bradford’, Amelanchier laevis and Magnolia x soulangiana are in full bloom (90 GDD Base 10oC). 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.
Monitor for newly hatched Balsam twig aphid nymphs (“stem mothers”) on terminal buds on fir, white spruce, Colorado spruce and juniper. Stem mothers (nymphs) will be feeding and getting ready to produce the next generation. The tiny, bluish grey aphid stem mothers can be found on/near 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). They will produce the next generation of nymphs that cause distortion of new 2009 needles. Photos: http://www.insectimages.org/browse/subimages.cfm?SUB=321http://ctrees.cas.psu.edu/pdfs/PestsofTrueFir.pdf
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.
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.
Pine shoot beetle adults may still be mating and laying eggs. 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.
– See more at: https://lawnsavers.com/nursery-and-landscape-report-2009/nursery-and-landscape-report-for-may-14-2009.html#sthash.GjoS22ov.dpuf
