What's Bugging Your Trees & Shrubs
For information on what's bugging your trees and shrubs, click the appropriate link below to go directly to the topic or scroll down the page.
Insect Pests
Aphids
Plants affected: Numerous indoor and outdoor plants
Symptoms: Severe infestations will cause curling/twisting of foliage, flowers to wilt and drop
Life Cycle: Eggs hatch on host plants in spring, these nymphs give birth to ‘daughters’, within days the daughters give birth – up to 30 generations per summer
Cultural Control:
• Ladybird beetles/larvae, lacewings are natural predators
• Strong jet of water to knock aphids off plants
Chemical Control: Doktor Doom House and Garden, End All
Ash Bark Beetle
Plants Affected: Ash
Symptoms:
• Wilting, yellowish foliage
• Check under bark for adults/galleries
Life Cycle:
• Adults overwinter in the bark of host trees
• In spring, females construct egg galleries (tunnels) between the bark and wood of host trees, which are typically stressed or damaged
• Larvae tunnel and feed in the inner bark of the tree during spring and summer
• Adults emerge in late summer
• One generation per year
Controls – Cultural or Non-chemical:
• Keep trees well-watered and fertilized
• Prune out dead or dying branches in early spring
• Remove old, badly infested trees
Controls – Chemical Controls: Doktor Doom Residual (yellow can) – insert straw into galleries to apply insecticide
Ash Leaf Cone Roller
Symptoms – Leaves rolled into cones – damage cosmetic
Life Cycle:
• Adult moths emerge in spring to early summer, mate and lay eggs on the leaves, twigs or bark of host trees
• Larvae hatch and roll leaves into cones to protect themselves as they feed, a stage that lasts up to 2 months
• Pupae may overwinter in the bark of host trees, or drop to the ground
• Usually one generation per year
Controls – Cultural or Non-chemical:
• Parasitic wasp is helping control
• Handpick small infestations
• Good leaf cleanup in fall
Controls – Chemical: None – spraying will kill beneficial insects that provide control
Ash Plant Bug
Plants Affected: Ash
Symptoms:
• Leaves turn yellow, may appear mottled or burned (similar to leaf hopper damage)
• Leaves may drop prematurely
• Damage is cosmetic
Life Cycle:
• Overwinter as eggs in the bark of ash trees
• In spring, eggs hatch and nymphs feed on the undersides of emerging leaves
• A second generation appears in July
• Adults are active from late summer until killing frost
Controls – Cultural or Non-chemical:
• Keep trees well-watered and fertilized, especially in droughts
• Remove feeding insects with a strong jet of water
Controls – Chemical: Ambush
Aspen Leafminer
Plants Affected: Aspen
Symptoms:
• Tunnels mined throughout leaf, can turn to blotches
Life Cycle:
• Overwinter in leaf debris, emerge in spring and lay eggs in leaves. Larvae feed between leaf layers, then emerge and overwinter in leaf debris or soil.
Controls – Cultural or Non-chemical:
• Infected leaves can be removed, all leaf debris should be raked up in fall and disposed of
Controls – Chemical: None
Aspen Leafrollers
Plants Affected: Aspen
Symptoms:
• Leaves rolled up tightly
• The culprit is a whitish caterpillar
• Cosmetic
Life Cycle:
• Overwinter as pupae in the soil and leaf debris on the ground
• Adult moths emerge in early spring and lay eggs on host trees
• Larvae hatch and construct shelters by rolling leaves up
• Mature larvae drop to the ground by late summer and pupate
Controls – Cultural or Non-chemical:
• Parasitic wasps help control
• Apply Horticultural Oil in early spring, before new leaves emerge
Controls – Chemical: Not available
Birch Leafminer
Plants Affected: Birch
Symptoms:
• Large dead patches (yellow/brown) in leaves
• Entire tree may appear to change to yellow or brown colour
• Insects will be found inside the leaves
• Damage is cosmetic
Life Cycle:
• Two generations per year
• Adult wasp emerges in late May
• Females insert eggs into leaves
• Larvae hatch and feed on the tissues between the leaves’ outer epidermal layers
• Mature larvae exit the leaves and drop to the ground to pupate, 1-2” deep
• Second generation hatches 2 weeks later; cycle repeats
Controls – Cultural or Non-chemical:
• Has been kept under control very well by beneficial insects
• Keep trees well-watered and fertilized, especially during drought
Controls – Chemical: Not available or necessary
Birch Sawfly
Plants affected: Birch
Symptoms: Clusters of yellow worms with black spots seen feeding around edges of leaves
Life Cycle: Pupae overwinter in soil; larvae emerge in spring and feed May to early July. A second generation may be seen in September
Controls – Cultural or Non-chemical: Handpick larvae
Controls – Chemical: Ambush, Malathion
Boxelder Midge
Plants Affected: Boxelder, Manitoba Maple
Symptoms:
• Leaves curl tightly, open to reveal white larvae
• Damage is cosmetic
Life Cycle:
• Adults emerge in spring when first leaves are unfurling
• Eggs are deposited into young folded leaves. Larvae appear a few days later and twisting/curling of foliage shortly after
• In mid-late June larvae drop to the ground, work their way into soil and construct cocoons. In late summer they pupate, overwinter in the soil
Controls – Cultural or Non-chemical:
• Prune off worst affected leaves (that can be reached), so less larvae drop to ground to pupate. Problems are aesthetic, since less than 50% of the tree is usually affected
Controls – Chemical: None available or necessary
Cottony Psyllid
Plants Affected: Ash, Elder (plants stressed by drought are more susceptible)
Symptoms: Twisted, distorted foliage—eventually browns and drops
Life Cycle:
• Overwinters as eggs laid along edges of bud scales
• Eggs hatch in May/June
Controls – Cultural or Non-chemical:
• Insect is very difficult to control once feeding begins. After leaf drop in fall (while temps still above 0) spray branches with Horticultural Oil (use dormant application rate)
• Again in early spring once leaves are about 3” long (this is when eggs are mature) spray again with Horticultural Oil (use summer application rate)
Controls – Chemical: You may spot adults dropping from tree on silken threads in late spring; if you notice these spray insects with Ambush
Cranberry Mite
Plants Affected: Cranberry/Viburnum
Symptoms:
• Leaves develop fuzzy white patches; commonly mistaken for powdery mildew
• Damage is cosmetic
Life Cycle:
• Adults overwinter in the bark of host plants
• Adults begin to feed on developing buds in spring, initiating gall development
• Female adults become encased in galls and lay eggs
• Young hatch and quickly mature and exit galls, repeating the cycle
• Several generations per year
Controls – Cultural or Non-chemical:
• Prune out affected sections as soon as damage noted
• Pick off affected leaves
• Apply Horticultural Oil after leaves drop in fall; reapply in early spring before new leaves emerge
Controls – Chemical: Not necessary or available
Elm Leafminer
Plants Affected: Elm
Symptoms:
• Leaves develop dead brown patches
• Insects will be found inside the leaves
• Damage is cosmetic
Life Cycle:
• Overwinters as pupae in the soil
• Adult sawflies are active from early May to early June
• Females insert eggs into the leaves of host trees in spring
• Larvae feed on the tissue between the epidermal layers of the leaves
• Mature larvae emerge from the leaves in mid-July and drop to the ground to pupate
• One generation per year
Controls – Cultural or Non-chemical:
• Keep trees well-watered and fertilized
• With small infestations, handpicking mined leaves is effective
• Remove all fallen leaves in fall
Controls – Chemical: None available or necessary
Elm Scale
Plants Affected: Elm
Symptoms:
• Honeydew, sooty mold on leaves and bark
• Branches die back
• Dark-coloured “bumps” noted on branches
Life cycle:
• Overwinter as eggs on the twigs of host plants
• Crawlers hatch in spring and disperse amongst suitable hosts by wind or animal carriers
• Mature scale mate; males then disappear and adult females become permanently stationary, developing an outer shell that protects them from harm
• By midsummer, adult females then begin to feed by sucking the sap from the host; eggs are laid beneath their bodies
• One generation per year
Controls – Cultural or Non-chemical:
• Apply a mixture of Horticultural Oil and Lime Sulphur in fall after leaves have dropped; reapply in early spring before new leaves emerge
• With small infestations, run gloved hand along bark to dislodge scales
Controls – Chemical: Not available
Hawthorn Lace Bug
Plants affected: Plants in the Rose Family, primarily Hawthorn, Pear, Cotoneaster, Saskatoon
Symptoms:
• Adults are small winged insects which appear to be covered in lace. Nymphs are dark brown to black and covered in varying amounts of spines
• Stippled or mottled leaves with many lace bugs present
• Feed in large numbers, leaves may be stained with their excrement
Life Cycle:
• Overwinter as adults (two generations per season)
• Black eggs are laid in clusters on the underside of leaves in early spring
• Nymphs emerge and feed on the underside of the leaves after about 3 weeks
• 5 instars; 1st generation of adults emerge in mid-summer, 2nd in fall
Controls – Cultural or Non-chemical:
• For small infestations, handpick
• Keep well-watered and fertilized
Controls – Chemical:
• For smaller shrubs, Doktor Doom House and Garden
• For larger shrubs or trees, Ambush
Leafcutter Bee
Plants Affected: Many, including Rose, Lilac, Ash
Symptoms:
• Half moon shapes cut out of leaves
• Use leaves to seal eggs into the cells of the hive
• Beneficial insect; may pollinate garden crops, do pollinate alfalfa
• Damage is cosmetic
Life Cycle:
• Overwinter as pupae in cells constructed out of leaf debris collected during spring and summer
• Adults emerge in spring and collect leaf material, pollen and nectar, and construct their cells
• Eggs are laid within the cells
• Larvae hatch and feed within the cells, and pupate before winter
Controls – Cultural or Non-chemical: Pick off affected leaves if desired
Controls – Chemical: Not necessary
Lilac Leafminer
Plants Affected: Lilac
Symptoms:
• Olive green patches that later turn into brown, blotchy areas
• Damage is cosmetic
Life Cycle:
• Mature larvae overwinter in soil, awake in spring and pierce leaf, laying eggs in late May in the evening, in rows on undersides of leaves. Hatch within 7-10 days
• Larvae bore into leaf and feed between layers for about 3 weeks, then surface, roll up in leaves and feed again
• 10 days later drop to ground, pupate and emerge again in early August for the second generation. These will feed until mid September then overwinter in soil
Controls – Cultural or Non-chemical:
• Remove affected leaves as they are noticed
• Keep well-watered and fertilized
Controls – Chemical: Not available
Maple Leafcutter Moth
Plants Affected: Maple, Birch, Saskatoon
Symptoms:
• Oval holes cut out of leaves, to be used by insect to “shield” itself
• Damage is cosmetic
Life Cycle:
• Overwinters as pupa, emerges in spring to lay eggs as leaves unfurl
• Larvae feed as leafminers for a bit, then emerge from mine and create a shelter using disks they have cut from leaf. As they mature they create bigger shelters using more disks from the leaf. Drop to the ground in fall to overwinter
Controls – Cultural or Non-chemical:
• Rake and destroy affected leaves
• Apply BTK as larvae emerge from mines
Controls – Chemical: Not available
Maple Mite
Plants Affected: Maple
Symptoms:
• Small, red, round “bumps” are seen on the surface of leaves in early to midsummer
• Damage is cosmetic
Life Cycle:
• Adults overwinter in the bark of host plants
• Adults begin to feed on developing buds in spring, initiating gall development
• Female adults become encased in galls and lay eggs
• Young hatch and quickly mature and exit galls, repeating the cycle
• Several generations per year
Controls – Cultural or Non-chemical:
• Prune out affected sections as soon as damage noted
• Pick off affected leaves
• Apply Horticultural Oil in fall after leaves drop; reapply in early spring before new leaves emerge
Controls – Chemical: Not necessary or available
Oak Gall Mite
Plants affected: Oak
Symptoms:
• Irregular “bumps” appear on foliage
• Damage is cosmetic
Controls – Cultural or Non-chemical:
• For small infestations, handpick affected leaves
• Good fall cleanup
• Apply Horticultural Oil in early spring, before new leaves emerge
Life Cycle:
• Adults overwinter in the bark of host plants
• Adults begin to feed on developing buds in spring, initiating gall development
• Female adults become encased in galls and lay eggs
• Young hatch and quickly mature and exit galls, repeating the cycle
• Several generations per year
Controls – Chemical: Not available
Oak Gall Wasp
Plants Affected: Oak
Symptoms: Round to oval galls about 1/2” in diameter found on twigs/branches in clusters. New galls are green, old ones brown
Life Cycle: Adult wasps lay eggs in leaf buds in fall. By early summer next season, larvae secrete chemical that causes plant tissue to enlarge (thereby creating gall). Gall envelops them. Late summer, adult emerges from the gall, mates and lays eggs again
Controls – Cultural/Non-chemical:
• Prune out galls
• Apply Horticultural Oil in early spring, before new leaves emerge
• Keep trees well-watered and fertilized
Controls – Chemical: Not available
Oak Phylloxera Aphid
Plants Affected: Oak – mostly English Oak
Symptoms: Yellow spots (“measles/chicken pox”) turn into dead spots in June. Turn leaf over, there will be a bright orange aphid
Life Cycle:
• Several generations per year
• Eggs overwinter in bark of host trees
• Nymphs hatch in spring and begin feeding on leaf undersides
• Mature aphids begin laying eggs in a circle around themselves, which will soon hatch into the next generation
Controls – Cultural/Non-chemical: Good fall cleanup
Controls – Chemical: Not available
Pear Slug
Plants Affected: Fruit Trees, Cotoneaster, Mountain Ash, Hawthorn
Symptoms:
• Browning and leaf skeletonizing in mid to late June and again late July/August
• Culprit is a small, dark-coloured, slug-like larva
• Damage is cosmetic
Life Cycle:
• Overwinter as pupae in leaf litter on the ground
• Adult flies emerge in late spring after hosts leaf out
• Females lay eggs into leaves, creating blisters
• 10-15 days later, slug-like larvae hatch and begin feeding on upper leaf surfaces
• Feeding continues for 2-3 weeks, skeletonizing leaves
• Mature larvae then drop to the ground to pupate
• A second generation emerges in late July; this causes the most damage
Controls – Cultural or Non-chemical:
• Pick off larvae, hose off with strong jet of water
• Bark mulch may deter adults’ emergence
• Parasitic wasps aid in control
Controls – Chemical: Ambush for large infestations
Poplar Borer
Plants Affected: Aspen, Willow, Poplar
Symptoms:
• Varnish-like resin and holes with boring dust on the stems. Larval galleries under bark
• Prefers main stems
• Damage could be confused with Poplar/Willow Borer
Life Cycle:
• Adults emerge late June. Females cut crescent shaped marks in bark in which to lay eggs
• Eggs hatch, larvae mine into bark and stay for summer and winter. Next spring enter the heartwood of tree and feed for 2 years; this is when you’ll notice sap
Controls – Cultural/Non-chemical:
• Use heavy gauge wire; locate holes and stick wire in to pierce and kill larvae
• Keep trees well-watered and fertilized
Controls – Chemical: Not available
Scurfy Scale
Plants Affected: Mainly Cotoneaster and other members of the Rose Family; also Ash, Aspen, Dogwood, Willow
Symptoms:
• Clusters of whitish to brown “bumps” found along branches
• Mistaken for fireblight, kills twigs/branches
Life Cycle:
• Overwinter as eggs on the twigs of host plants
• Crawlers hatch in spring and disperse amongst suitable hosts by wind or animal carriers
• Mature scale mate; males then disappear and adult females become permanently stationary, developing an outer shell that protects them from harm
• By midsummer, adult females then begin to feed by sucking the sap from the host; eggs are laid beneath their bodies
• One generation per year
Controls – Cultural or Non-chemical:
• Prune out affected branches/stems (bad infestations on Cotoneaster may necessitate a full rejuvenation prune to ground level)
• Natural predators include lacewings and lady bugs
• Apply a mixture of Horticultural Oil and Lime Sulphur in fall after leaves drop; reapply in early spring before new leaves emerge (use at half strength on Cotoneaster)
• Keep well-watered and fertilized
Controls – Chemical: Malathion at end of June
Tent Caterpillar
Plants affected: Mainly Aspen and Poplar; also Apple, Ash, Birch, Choke Cherry, Elm, Maple, Oak, Willow
Symptoms:
• Masses of relatively large, colourful caterpillars are found in spring, constructing “tents” of silk for shelter
• Causes major defoliation on host trees
Life Cycle:
• Several different species with similar life cycles
• One generation per year
• Adult moths lay eggs in summer, which overwinter in the crotches of trees
• Eggs hatch in spring; larvae feed for 4-8 weeks before maturing
Controls – Cultural/Non-chemical:
• Remove ‘tents’ – best done in late evening or early morning
• Handpick, scrape cocoons off of branches in summer
• Apply BTK while larvae are present; reapply as needed every 5-7 days
Controls – Chemical: Not necessary; BTK very effective
Viburnum Leaf Beetle
Plants Affected: Viburnum/Cranberry
Symptoms:
• Early damage appears as pin pricks—by June skeletonizing apparent
• In summer, lines of holes (egg chambers) can be seen along twigs of current season’s growth
Life Cycle:
• Eggs hatch in May, larvae begin feeding
• In June larvae drop to ground to pupate. Adult beetles emerge, females chew holes in twigs, lay eggs from summer to frost
Controls – Cultural/Non-chemical: Early spring examine twigs for holes—prune out
Controls – Chemical: Doktor Doom House and Garden—as leaves expand in spring, look for larvae and spray these. Adults difficult to spray as they fly away when disturbed
Willow Leaf Blotch Miner
Plants Affected: Willow, especially Laurel Leaf
Symptoms:
• Large brown blotches on leaves will start to ‘bubble’ revealing the larvae feeding between leaf layers
• Leaves eventually yellow and drop
• Damage is cosmetic; does not usually kill trees
Life Cycle: Adult moths overwinter, emerge in spring and lay eggs on undersides of leaves. Eggs hatch, larvae feed, spin silken covering on leaves or on ground. Adults emerge in August, overwinter
Controls – Cultural or Non-chemical:
• Rake affected leaves well in fall
• Apply Horticultural Oil at summer dilution rate, in spring RIGHT AFTER leaves emerge
• Keep trees well-watered and fertilized
Controls – Chemical: Not available
Woolly Bear Caterpillar (Spotted Tussock Moth Larvae)
Plants Affected: Numerous
Symptoms:
• Fuzzy, black and yellow caterpillars are seen feeding on the edges of leaves
• Damage is cosmetic and usually minimal
Life Cycle:
• Overwinters as pupa in the soil
• Adult moths fly from mid-June to mid-July, laying eggs on the undersides of host plants
• Larvae hatch about 1 week later and begin feeding on leaves
• Larvae will migrate if food source runs out or the host is too mature
Controls: No control recommended
Diseases
Apple Scab
Plants Affected: Apple
Symptoms:
• Fruit develops distinctive scabs on the skin
• Leaves develop brown “scorched” areas; damage often mistaken for fireblight
Life Cycle:
• Fungus overwinters on infected leaf and fruit debris from the previous season
• Spores travel on the wind and infect wet leaves, flowers, and fruit
Controls – Cultural or Non-Chemical:
• Rake up leaves and discard fruit
• Keep trees well-watered and fertilized
• Plant disease resistant varieties
Controls – Chemical: None available
Black Knot
Plants Affected: Members of the Rose Family and especially Prunus; primarily Schubert Chokecherry, Wild Chokecherry, and Mayday
Symptoms:
• Initially, new knots start out as branch swelling
• Large black ‘knots’ (cankers) appear on branches the following year
• Spreads to the trunk, eventually killing the tree after a number of years
Life Cycle:
• Mature cankers release spores in summer, which travel on the wind
• Spores infect wet tissue on susceptible plants, especially those that are stressed out or damaged
Controls – Cultural or Non-Chemical:
• Prune out knots at least 12 inches below affected area, clean pruners with bleach/alcohol after every cut
• Dispose of infected branches by burning or burial
• Keep trees well-watered and fertilized
Controls – Chemical: None available
Black Spot
Plants Affected: Numerous, especially Rose
Symptoms:
• Round black spots form on leaves, stems and leaf stalks
• Plants will most likely not be killed but can be severely stressed
Life Cycle:
• The fungus overwinters on infected leaf debris from the previous season
• Spores travel with wind and colonize on wet foliage
Controls – Cultural or Non-Chemical:
• Affected leaves or flowers can be pruned out and discarded. DO NOT COMPOST
• Keep plants well-spaced to improve air circulation
• Water in the morning and avoid wetting the foliage
• Keep affected plants well-watered and fertilized
• Cut back all dead foliage to ground level in fall to prevent reinfection next year
• Natria Bio-fungicide can be applied as a preventative in 5 day intervals, starting in June
Controls – Chemical:
• Safer’s Defender can be sprayed in 7 day intervals as a preventative on plants that have been previously infected
• Garden Sulphur can be dusted onto affected plants to suppress spores
Aspen Bronze Leaf Disease
Plants Affected: Poplar, Swedish Columnar Aspen, Trembling Aspen
Symptoms:
• First appears in mid-summer; leaves form yellowish, orange brown or reddish brown discoloration near leaf margins
• Discolored areas expand to cover the whole leaf except for the veins
• As discoloration spreads, it turns bronze in color
• Branch die back can occur as disease spreads; the entire tree can be killed in 3-5 years
Life Cycle:
• Fungus overwinters on infected leaf debris, both on and off host trees
• Spores travel on the wind to infect other trees in spring and summer
Controls – Cultural or Non-Chemical:
• Remove infected branches and leaves, disinfect pruners with bleach after each cut
• Good fall clean-up is essential
• If any infected leaves or branches are on the tree in the fall remove them
• Keep trees well-watered and fertilized
• Avoid overplanting aspen and poplar; consider alternatives for Swedish Columnar Aspen such as ‘Dakota Pinnacle’ or ‘Parkland Pillar’ Birch
Controls – Chemical: None available
Cytospora Canker
Plants affected: Evergreens
Symptoms:
• Needles start off yellow, in summer turn purple
• During periods of wetness, gelatinous threads can be seen
• Cankers form with sunken ridges, girdle branches, cause dieback
Life Cycle:
• Secondary fungal disease—moves in on sun scalded wood, stressed trees
• Spores are released onto the wind from gelatinous fruiting bodies
Cultural Control:
• Prune out affected sections
• Keep trees well-watered and fertilized
Chemical Control: None available
Fireblight
Plants Affected: Rose Family – Apple, Crabapple, Pear, Mountain Ash, Cotoneaster
Symptoms:
• Dramatic wilting at tips of new growth—shepherd’s crook
• Scorched appearance of leaves and clear, amber liquid may be seen oozing from plant
Life Cycle:
• Bacteria overwinter on cankers on infected trees
• Splashing rain or insects transfer bacteria from infected trees to healthy ones during the growing season
Controls – Cultural or Non-Chemical: Prune out affected branches 12” below infected area. Disinfect tools with bleach between EVERY cut
Controls – Chemical: Copper or sulphur—spray on plant in mid-June—this acts as a preventative. Sprays do not offer control once bacteria is present
Juniper-Hawthorn Rust
Plants Affected: Juniper/Cedars, and Hawthorn, Crabapple, Apple, Mountain Ash
Symptoms and Life Cycle
• Galls form on juniper/cedar branches
• After spring rains, galls ooze gelatinous ‘spore horns’
• On alternate hosts (hawthorn, etc.), yellow-orange spots show, later become orange-yellow surrounded by red bands. These will then release spores in June/July, infecting junipers/cedars in the area
Controls – Cultural or Non-Chemical:
• Eliminate a host (note: neighbours could still have one of the hosts)
• Prune out juniper galls in late winter/early spring before spore horns emerge
• Keep plants well-watered and fertilized
Controls – Chemical: Copper fungicide (Bordo) should be sprayed on Hawthorns and other alternate hosts foliage as plants start to bloom, then repeated twice at 7-10 day intervals
Lilac Blight
Plants affected: Lilac, Blueberry, Maple
Symptoms:
• Early spring foliage curls up/twists
• Brown spots with yellow halos
• Infected leaves and flower buds emerge and quickly turn black and die
Life Cycle:
• Bacteria overwinter on leaf debris and in the soil
• Emerges in the spring when weather is cool and rainy
• Spreads via splashing water or insects
Controls – Cultural/Non-chemical:
• Good fall clean-up of all leaf debris
• Keep plants well-watered and fertilized
Controls – Chemical: Apply copper spray as a preventative in spring
Oak Leaf Blister
Plants Affected: Oak
Symptoms:
• Slight yellowing of leaf surface followed by raised blisters
• Tree may prematurely defoliate in late summer
Life Cycle: Fungus overwinters on bud scales and in bark crevices
Controls – Cultural or Non-Chemical: Lime Sulphur applied to bark crevices and bud scales in fall or spring, when leaves are not present
Controls – Chemical: None available
Powdery Mildew
Plants Affected: Numerous, especially Beebalm, Columbine, Delphinium, Goldenrod, Jacob’s Ladder, Lungwort, Meadowsweet, Speedwell, Stonecrop, Summer Phlox, and others
Symptoms:
• White powdery spots, yellowing leaves
• Plants cannot manufacture as much food as they need; severe infestations can kill or severely stunt plants
Life Cycle:
• Fungus overwinters on infected leaf debris from the previous season
• Spores travel on wind and infect wet foliage
• Most prolific during summer weather where days are hot and dry and nights are cool and humid
• Weeds are frequently responsible for harbouring and spreading the disease
Controls – Cultural or Non-Chemical:
• Keep plants well-spaced to improve air circulation
• Clip off infected sections
• Perennials that are badly infected can even be cut back to ground level and allowed to regrow
•Keep well-watered and fertilized; liquid kelp and high potassium fertilizers aid in recovery
• Water in the morning only and avoid wetting the foliage
• Cut back all dead foliage to ground level in fall to prevent reinfection next year
• Keep beds well weeded
• Natria Bio-fungicide can be applied as a preventative in 5 day intervals, beginning in June
Controls – Chemical:
• Safer’s Defender can be applied as a preventative in 7 day intervals, beginning in June
• Garden Sulphur can be dusted onto affected plants to suppress spores
Raspberry Blight - Spur
Plants affected – Raspberry
Symptoms:
• Edge of older leaves have V shaped lesions. Advances to mid veins then to the leaf axil where new growth occur
• Lowest leaves affected first, then moves upwards
Life Cycle: Spores are discharged from May to August coming from old fruiting canes. Secondary spores (conidia) are also produced and those spores splashed about in July/August probably cause the most damage
Cultural Control: Provide good spacing between rows
Chemical Control – Apply preventative applications of Natria or Copper starting in mid to late June
Raspberry Blight - Cane
Plants Affected: Raspberry
Symptoms:
• Purple spots with grey-white centres form on new canes, leaves. Spots enlarge to form sunken pits. On second-year canes lesions can coalesce into cankers that girdle the cane
• Fruit symptoms include shrunken brown druplets or withered, dry seedy fruit
Life Cycle:
• Ascospores are rain-splashed and air-borne from infected canes in early spring
• Conidia are rain-splashed from overwintering infected canes in the spring and throughout the summer to new growth
• Infection requires three to twelve hours of wetness; only very young green tissue is infected
Controls – Cultural/Non-chemical:
• Prune out damaged canes
• Apply preventative applications of Natria Bio-fungicide starting in mid-June every 7 days
Controls – Chemical: Apply preventative applications of Copper Spray starting in mid to late June every 10 days
Saskatoon-Juniper Rust
Plants affected: Saskatoon
Symptoms:
• Infected leaves and berries develop yellowish-orange spots
• Later in season, spots may be covered with spiny projections (like whiskers)
• leaf can tolerate large quantities of spots, but one spot ruins the berry
• Two hosts; overwinters on Juniper plants
Controls – Cultural/Non-chemical:
• Remove junipers growing nearby
• Keep plants well-watered
Controls – Chemical: Preventative sprays of copper fungicide starting in June
Shothole Fungus
Plants affected: Numerous, in particular Prunus (Plum, Cherry, Chokecherry, Apricot)
Symptoms: Numerous tiny, perfectly round holes appear right through the leaves
Life Cycle: Overwinters in leaf debris – is caused by both a bacteria and fungus
Cultural Control: Good fall clean-up
Chemical Control: Copper fungicide in spring as a preventative starting in mid-June
Cultural Disorders
Disorders are plant abnormalities that are caused by environmental factors such as nutrient availability or temperature (not pests or diseases). Typically, disorders may make your plant look different than expected but unless severe, are not usually overly harmful.
Chlorosis
Symptoms:
• leaves are yellow but veins remain green, may be some browning on the margins of leaves
• will be evident first on new growth, then work back to older leaves on a branch
Control:
• ensure loose, well-drained soil, avoid overwatering
• high soil alkalinity can also be a cause, plants can be fertilized with iron chelate for recovery
Frost Crack
Symptoms:
• vertical cracks present in bark on trunks of trees
• fruit trees very susceptible to this
Controls:
• due to fluctuating temperatures in winter months
• mulch bases of trees with bark mulch, ensure plants are well hydrated before final freeze up in autumn
Gummosis
Symptoms:
• very common on fruit trees, especially cherries
Control
• causes vary from mechanical damages such as sapsucker damage, squirrel damage, wood boring insects or delayed winter injury, which is common in fruit trees
• beyond avoiding these, let the wounds heal over on their own
Herbicide Damage
Symptoms:
• curling or cupping leaves
• discoloration between veins
• twisted, elongated stems
Control:
• use all herbicides according to label, note that herbicide can drift for several miles, it’s very difficult to ascertain where chemical drifts from
• keep damaged plants well-watered, most plants will recover
Overwatering
Symptoms:
• wilting, yellowing leaves
• leaves will yellow from outside in
• Note: wilting is a symptom of BOTH over and underwatering, if plants are wilting don’t assume they require moisture until soil is checked by hand
Controls:
• plants in lower lying areas will suffer in times of heavy rains; plant appropriate species in these areas
• for new and established plants, water only as required; check soil prior to watering
Underwatering
Symptoms:
• wilting, crispy or browned leaf edges
Controls:
• water, especially for new transplants should be monitored daily during periods of extreme heat
• for new transplants, stick your hand into the soil to determine if moisture is required