Holy Cow its dry out there, lawns look like they are starting to go dormant. Newly planted trees and shrubs are really starting to suffer. I’ve got American goldfinches trying to drink from my Hummingbird feeder. And my colleague said he was watering some plants in his garden and a Hummingbird came along and drank from the stream of water in mid-flight.
For Plant Phenology Indicators this week, the Aesculus hipposcastanum (horsechestnut) are in full to late bloom, Robinia pseudoacacia in full bloom, the Viburnum opulus (snowball bush) are in full bloom, the Cornus alternifolia (pagoda dogwood) and the Weigela florida are in full bloom. This puts us at about 200-300 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.
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 should be finishing up. Leaves are hardening off and much less susceptible to disease. For those cultivars that are very prone to apple scab, you may want to apply one more protectant fungicide before the next rain.
Below are the links to the updated Risk Maps For Fire Blight. Since most apple growing regions are now beyond the critical growth stage for blossom infections we will do the last set of maps on Friday May 29. IT is important to watch for late blossoms, called ‘rat tail’ blossoms, which are very susceptible to infection.
Gymnosporangium rusts (e.g. Cedar-apple rust, Cedar-hawthorn rust, Cedar-Quince rust) are sporulating on a limited basis due to extended dry conditions in many 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, before rain events in the next week or so.
Fletcher scale (Taxus scale) nymphs are actively feeding on Thuja and Taxus and are getting larger. They have a distinctive white stripe down their backs. You’ll probably notice the honeydew first. This scale is difficult to manage at this size but an application of systemic insecticides may help reduce populations in hot spots. It is entering its most rapid growth phase.
Crawlers of Oystershell Scale are starting to hatch in many areas. These crawlers are tiny and brown and very susceptible to insecticides including insecticidal soap and the summer rate of horticultural oil. This scale species can be found on several deciduous trees including ash, magnolia, maple, hackberry, willow and lilac etc.
For those of you growing Thuja with a high percentage of Juniper tip midge, now is the time that they are most vulnerable to systemic pesticides. The larvae of the midge can cause significant damage and stunting on Thuja. Not to be confused with………
GYPSY MOTH: now is the time when larvae are hiding in bark crevices during teh warmest part of the day. These mid-instar larvae are feeding on foliage, some control can be achieved using Bacillus thuringienesis (Dipel, Foray) and spinosad (Success) insecticide. Dipel doesn’t work as well on older larvae but Success should be effective after larvae reach 1 inch long (head capsule turns yellow). Don’t forget to monitor Colorado spruce for Gypsy moth larvae!
Euonymus webworm (Yponemeuta cagnagella) is having a merry time on Euonymus alatus (burning bush). These webworms are difficult to manage with pesticides because their web repels water. Prune out and destroy webworm nests where possible.
Elm leaf beetle (Xanthogaleruca luteola) larvae can be found feeding on Siberian elms (Ulmus pumila) at this time. Look for greenish larvae with black longitudinal stripes feeding on the undersides of leaves. Damage can be significant where populations are high. Treat with insecticidal soap when larvae are small. More traditional insecticides may be necessary for management (orthene, sevin, success).
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. Emerald ash borer adults are just starting to emerge (black locust blooming) and will be active for several weeks.
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. Bark applications of insecticides applied now can help reduce the success of newly-hatched larvae boring into bark. 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 are feeding on beech. 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 becoming a problem in some areas as they are feeding on the newest 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 when they are small and get more tolerant as they get older. 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).