It’s our favorite time of year, the temperatures are up and down like a yo-yo, the UV index is extremely high, the black flies are still biting (me at least) and a new batch of mosquitoes has just hatched (and you know deer fly season isn’t that far away), frost warnings are still on the radio and the phone is vibrating right off the table. Its spring in Southern Ontario! Weather experts are predicting a nice, warm summer but summer precipitation may be ample in our region. Quite a contrast from the drought California is experiencing.
For Plant Phenology Indicators this week, the Aesculus hipposcastanum (horsechestnut) are in early bloom,the Cercis canadensis (redbud) are in late bloom, ,the Prunus x cistena (purple-leaf sandcherry) are in late bloom. This puts us at about 110-195 GDD Base 10C. Plant phenology models for IPM can be found starting on pg. 39 of OMAFRA Guide 841, Guide to Nursery and Landscape Plant Production & IPM. Many of these models are based on Donald Orton’s COINCIDE.
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.
The Crop Protection Guide for Nursery and Landscape Plants (OMAFRA publication 840) contains the crop pest recommendations for nursery and landscape plants that was previously found in publication 383. Publication 840 is a .pdf file, accessible online and on cd.
Pest recommendations can also be found on our online, searchable database: www.nurserytracker.com. Check out NurseryTracker on your phone or tablet!!!
Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape database to help ID your problem pests.
Cool, dry, low humidity conditions in southern Ontario are a welcome reprieve for many as this weather does not support infection from many of our fungal and bacterial diseases. With no rain in the forecast until early next week, re-applications of fungicides can likely wait until just before the next rain event. The exception is for those crops being irrigated with overhead sprinklers.
Where new growth is emerging on Austrian pine, Scots pine and mugo pine, monitor for signs of Dothistroma needleblight (Dothistroma septosporum) on last year’s foliage and older. Initial infection appears as reddish-brown spots on the needles. The spots turn into a reddish-brown band with green tissue below and brown needle tissue above. Eventually infected needles turn completely brown and drop. Not so nice. We’ve had a couple of rainy summers so its no surprise this disease has shown up in production. This disease may be confused with Brown spot (Mycosphaerella dearnessii). Protect previous year’s growth with fungicides (Copper, Daconil) before wet, cool weather. A second mid summer application and third late summer/early fall application of fungicides will help protect 2015 needles. Yes that’s right, new growth resists infection and become susceptible mid-summer to early fall.
Fungicide applications for needlecast diseases of pine (e.g. Diplodia tip blight) and spruce (Rhizosphaera and Stigmina needlecast) can wait until just before the next rainy period. Check your local forecast.
Fungicides that protect new foliage against Apple Scab can also slow down a bit. Consider re-applying to susceptible foliage just ahead of the next significant rain event. Apple scab infections can lead to chlorosis and premature leaf drop. Some cultivars of Malus that are reported to be highly tolerant to Apple Scab:
M. halliana var. parkmanii
‘Purple Prince’ Redbud Red Jewel™
‘Sargent’ ‘Sugar Tyme’ ‘Silver Moon’
Below are the links to the Prediction Models for Fireblight in Ontario. Find your location on these maps to determine the level of risk forecasted for fireblight on apple and pear. Use these prediction models to make sprayer application decisions. Streptomycin, Kasumin and copper are all registered to manage this disease in the nursery.
Gymnosporangium rusts (e.g. Cedar-apple rust, Cedar-hawthorn rust, Cedar-Quince rust) are sporulating on a limited basis due to minor precipitation events in some areas. Sporulating structures are partially emerging and then drying out again. Some spores are landing on apple, crabapple, serviceberry pear, quince and hawthorn to infect leaves. Sporulation is not complete for a lot of overwintering Gymnosporangium galls on Juniper. Continue to protect foliage, especially before rain events in the next week or so.
Pear Trellis Rust will be sporulating soon on Savin-type Junipers, likely in the next batch of warm, humid/wet weather so fungicide application to pear trees should be in place before the next warm rain.
GYPSY MOTH: first generation larvae are blowing around on threads as a method of dispersal. When larvae start to feed on foliage, some control can be achieved using Bacillus thuringienesis (Dipel, Foray) and spinosad (Success) insecticide in the first 2 weeks after egg hatch. Dipel doesn’t work as well on older larvae but Success should be effective then. Don’t forget to monitor Colorado spruce for Gypsy moth larvae!
Some species of scale insects (pine needle scale, oystershell scale) that overwinter as eggs will be hatching into crawlers. Remember crawlers don’t all hatch at the same time, where insecticide applications are warranted, 2-3 applications about 7-10 days apart are usually necessary. Some low toxicity choices include the summer rate of horticultural oil and insecticidal soap. New insecticides registered for scale insects on nursery crops include Kontos (foliar and drench).
Once ash trees have completely leafed out to full size, injectable insecticides may be used to protect the trees from new infestations of Emerald Ash Borer (Agrilus planipennis). Trees must be actively transpiring in order to maximize insecticide uptake into the cambium. Registered injectable insecticide products include: AceCap 97, Confidor 200 SL, Ima-jet and Tree-Azin. Check out the Management Strategy for Emerald Ash Borer and Bronze Birch Borer at:http://www.omafra.gov.on.ca/english/crops/insects/eab-bbb-manage.htm For those of you interested in biocontrol of Emerald ash borer in North America, click HERE.
Birches with a history of BRONZE BIRCH BORER infestation, 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 light 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 (River birch) and its selections have been shown to be quite tolerant to BBB attack. Check out the Management Strategy for Emerald Ash Borer and Bronze Birch Borer at: http://www.omafra.gov.on.ca/english/crops/insects/eab-bbb-manage.htm
WOOLLY BEECH APHID will be starting to feed on beech as new leaves continue to emerge over the next week. These aphids are small and green but they cover themselves with bright white, woolly strands and produce honeydew droplets that cling to the woolly masses. Populations are usually not threatening to tree health but applications of Insecticidal Soap can be very effective at reducing populations of young nymphs, especially when adequate spray coverage on LEAF UNDERSIDES.
Where HONEYLOCUST PLANT BUG was a problem in the past, monitor trees for overwintered nymphs of plant bugs. Plant bug nymphs are feeding on newly emerging leaves, shake new leaves over a clipboard to quantify populations of plant bug nymphs. Most contact insecticides work very well against this pest. Reducing populations now can help since multiple generations will be cycling over the next few weeks.
Are your Viburnum leaves disappearing? VIBURNUM LEAF BEETLE larvae are feeding on the undersides of foliage at this time (V. trilobum, V. opulus, V. dentatum etc.). 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 (Success, Actara, horticultural oil).