Malus ‘Rosseau’ at Royal Botanical Gardens
PLANT PHENOLOGY indicators this week,
A) north of 401, include: Cercis canadensis (redbud, full bloom); Amelanchier laevis (serviceberry, late bloom); Syringa vulgaris (common lilac, early bloom) (150-200 GDD base 10oC)
B) Niagara: Aesculus hippocastanum (horsechestnut, full bloom); Prunus serotina (black cherry, full bloom)Syringa vulgaris (lilac, full bloom); Spiraea vanhouttei (bridal wreath spirea, full bloom) (150-200 GDD base 10oC)
If you are referring to the Monitoring tables in the 2009 edition of publication 383, Nursery and Landscape Plant Production and IPM, look at Tables starting on pg. 66.
Environment Canada is forecasting a spectacular week, what fantastic weather for shopping in the garden centre and planting ornamentals in the garden. There is a small chance of rain for much of southern Ontario for Tuesday but its sunny skies after that.
Homeowners, landscape professionals and nursery growers are still finding carnage from “the Great Winter of 2014”. It’s amazing the variety and size of ornamental plant losses due to desiccation and low temperature injury this spring. Evergreens were hardest hit, including conifers and broad leaf ornamentals such as boxwood and Euonymus in the landscape, field and in container production. I was standing in a polyhouse last week where 90% of the native beech trees were dead yet all of the wisteria survived and were blooming in containers beside the poor beech. Fall hit fast and hard in November and a lot of plants did not have enough time to acclimate for winter. Others did not have an adequate root system and storage. Some, like the native beech and holly just can’t take the freezing conditions especially growing above ground in a pot. My redbud in Guelph? It’s showing signs of life but there aren’t many flowers this year.
DECIDUOUS WOODY AND HERBACEOUS
Monitor for the very beginning of powdery mildew on crops such as Physocarpus in production over the next few weeks. Monitor for white, powdery residule on the tops and bottoms of leaves. This is a very wooley type of powdery mildew and is very aggressive on this host (causes leaf and stem dieback). Protect new foliage with fungicide applications (e.g. Switch, Milstop, Regalia (bio)) where disease pressure is moderate to high. Prune out and destroy light infestations.
FIREBLIGHT of apple and pear. The window of infection starts once FLOWERS ARE BLOOMING. Most fireblight infections enter the delicate flower tissue. Protect flowers and emerging leaves with bactericidal products such as Kasumin (Grp 24) and Streptomycin (Grp 25) during bloom. For suppression of fireblgiht in the landscape with Class 11 biological fungicides, Blightban C9-1 and Bloomtime can be used during bloom of apple and pear. CHECK IT OUT! Prediction models for Fireblight Activity in southern Ontario May 23-29 can be found here:
http://www.omafra.gov.on.ca/english/crops/facts/fireblight-2.htm (English)
http://www.omafra.gov.on.ca/french/crops/facts/fireblight-2.htm (French)
APPLE SCAB causes diffuse-looking spots along leaf veins and often leads to premature leaf drop in JuneNote: copper should be avoided beyond 1/2″ green tip stage (as leaves are emerging) to avoid potential phytoxicity issues. Where ornamental crabapples are further along in leaf emergence, try fungicides such as Nova (Grp 3, rotate with other fungicides to avoid resistance), Pristine (Grp 7, 11), Compass (Grp 11), Captan (Grp M) and Manzate (Grp M) . For supression of apple scab in the landscape with Class 11 fungicides, Serenade Max (Bacilus subtilis) and sulphur can be used to help protect emerging foliage from this disease.
Dutch Trig is available for Dutch Elm Disease on Ulmus americana species in Canada. This injectable treatment contains a biological organism that induces a plant immune response to help stimulate the tree’s defense mechanisms for fighting off DED infections. Arbotect-20-S (thiabendazole) is the registered injectable fungicide treatment. Injections should be made on sunny days during leaf emergence to maximize uptake.
Canopy dieback on green ash due to EAB
Callus on larval tunnel of white birch from BBB
Ash trees have leafed out and 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 and Tree-Azin. Check out the Management Strategy for Emerald Ash Borer and Bronze Birch Borer here.
WOOLLY BEECH APHID is feeding on beech as new leaves emerge over the next week or two. These aphids are small and green but they cover themselves with bright white wooly strands and produce honeydew. Population 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.
In PRODUCTION NURSERIES where black vine weevil larvae are a problem in container crops (e.g. perennials, evergreens), nematode applications should be finishing up. In container production, Met 52 Granular can be used prevenatively, at the time of potting, to help control all stages of black vine weevil. In the LANDSCAPE and GARDEN, check for overwintered LARVAE of black vine weevil on Rhododendron, Taxus, Thuja, Euonymus etc. in the garden and treat with nematodes when soil temperatures warm up.
Aphids are showing up on the newest growth of herbaceous and woody ornamentals this spring! Green peach aphid is one of the most common species and melon aphid and foxglove aphid are also quite common.
Green Peach Aphid (U. California)
Black Bean Aphid (D. Fenwick)
In early spring we often see the black bean aphid (Aphis fabae) on deciduous flowering shrubs and Euonymus. Various insecticides are registered to manage aphids in nurseries including Endeavor, Tristar, Trounce. Low toxic landscape use choices for insecticides include insecticidal soap. In outdoor grown container nurseries, we often see aphids first on Euonymus alatus and Spiraea this week.
Now is the time to order your pheromone lures and sticky wing traps for Peach tree borer and Viburnum Borer. Are you seeing sparse foliage and dieback on your ornamental Prunus? Peach tree borer (Synanthedon exitosa) larvae can be found just inside the bark of stems at/below the soil line of ornamental Prunus at this time. Look for cankered regions and chewed bark/wood in the lower stems of Prunus (Prunus x cistena) as a sign of larval damage.
The clearwing moths that emerge in a few weeks time 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 will be starting to emerge in container production in a few weeks. To purchase traps, try ordering from IPM suppliers such as http://www.naturalinsectcontrol.com and Plant Products. Some growers are trying soil drench applications of beneficial nematodes (Steinernema carpocapsae) after peak adult flight, as a biological way to control hatching larvae. We have seen some pretty good suppression of clearwing moth borers using nematodes as a drench!
EVERGREENS
Monitor for needlecast and blight diseases on older foliage where new foliage is emerging on pine and spruce. Diplodia tip blight on 2 and 3 needled pines and Rhizosphaera needlecast (see photos above) 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 can also be found on spruce and 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. Where there is a history of damage, treat with registered fungicides (copper oxychloride, Banner Maxx, 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 so management can be difficult.
Spruce budworm (Choristoneura fumiferana) is feeding on the new needles of trees in the SW. In spring, the overwintering larvae feed on male flowers and may mine buds and needles. Older larvae feed on expanding shoots, destroying them before they can fully elongate. The small, green larvae are detected by the small patches of browned foliage that have tiny nests made of shoots wrapped together by silk. Larvae can cause defoliation and also browning of the needles. B.t. (Dipel) is an excellent biological insecticide for suppressing spruce budworm populations in mid-late spring (spray foliage in the evening).
Monitor for eggs and the first generation of Euonymus scale crawlers in container production, they should be hatching in the next week or two. Euonymus scale look like tiny white (males) and brown, sea-shell (females) flecks along twigs and the undersides of leaves. Look for bright, orange crawlers around populations of adults and on the undersides of leaves and twigs. Where insecticide applications are warranted, multiple applications (Kontos, Cygon, Orthene) may be required to get good knockdown since crawler emergence is staggered over a few weeks. Kontos (spirotetramat) is registered as a soil drench in container grown Euonymus. Lower toxicity options include insecticidal soap and the summer rate of horticultural oil.
Take a look at the roots of poor looking turf and field grown ornamentals and look for populations of European chafer, May/June Beetle larvae and other white grub species in the soil. Preventative applications of Intercept (imidacloprid) are registered for white grubs (nursery production) and the application period is in June and July (during the adult flight period). Beneficial nematode applications are not recommended this time of year and are much more effective when applied to early instar larvae, mid-late August for European chafer.
Monitor for Spruce spider mites on new growth (especially on east side of the tree), nymphs and adults will be feeding on shoots. Miticides registered for SSM include Floramite and Kanemite. Miticides may be required where pest pressure is moderate to heavy.
PLEASE NOTE: The previous 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 2013 Crop Protection Guide for Nursery and Landscape Plants (previously 383, now publication 840) can now be found at:http://www.omafra.gov.on.ca/english/crops/pub840/p840order.htm
This 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. The supporting guide publication 841, GUIDE TO NURSERY AND LANDSCAPE PLANT PRODUCTION AND IPM will be online soon.
Nursery-Landscape Insect Pest ID: Dave Cheung’s Common Pests of Nursery-Landscape database to help ID your problem pests. Check out http://www.dkbdigitaldesigns.com/clm
ONnurserycrops Blog 