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Insect of the Month - Woolly Elm Aphid / Woolly Apple Aphid | |
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| Eriosoma americanum / E. lanigerum
Crops Affected:
Saskatoon berries (WEA/WAA), elm (WEA/WAA), apple (WAA), hawthorn (WAA), mountain ash (WAA)
Life Cycle:
- Overwinters as an egg in bark crevices on elm
- 1st generation (wing-less) feeds on elm leaves
- Winged generation produced in mid-June to mid-July
- Migrate to Saskatoon plants (about 2 weeks after purple lilac blooms) throughout month of July
- Nymphs born upon landing on plants; migrate to roots; rapid population increase
- Colonies found on roots July through October
- Winged generation produced in September and returns to Elm (do not overwinter on roots of Saskatoon)
- Younger, more succulent roots = most susceptible to infestation; 2nd & 3rd growing season
Symptoms:
- Above ground
- Lack of vigour in young plants
- Failure to leaf out or partial leafing out, followed by early season plant death
- Early/premature fall colour change (late July/early August)
- Below ground
- White, woolly masses on plant roots
- Typically found late in the year of infestation or in the following year
- Infected roots may have a purplish / blue to whitish discolouration
- Roots may be swollen and puffy
- Presence and damage may not be noticed until after infestation (too late?)
- Symptoms on elm
- Causes curling of elm leaves
- Produce copious quantities of honeydew and secrete a powdery white wax
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Curled elm leaf, with Woolly Elm Aphid & their honeydew & waxy flocculence evident |
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Swollen roots and fluffy/woolly residues – indicates a past/present WEA infestation |
Photos by Robert Spencer |
Monitoring:
- Watch for development of above-ground symptoms in spring
- Inspect roots of symptomatic plants by digging a 15cm (6 inch) trench 30cm (12 inches) away from the base of the plant, removing soil from the outside of the trench towards the base of the plant.
- Yellow sticky traps can be used to monitor aphid migration.
Management:
- Orthene 75%SP (acephate) application (soil injection) can be made to bearing and non-bearing plants (11 month PHI on bearing plants)
- Apply mid-July to early August (better as early as possible) – after harvest for bearing plants
- Admire 240F / Alias 240SC (imidacloprid) – soil drench spray application to bearing and non-bearing plants (14 day PHI on bearing plants)
- Apply early to mid-July – when 75-100% of aphids have migrated
- Avoid planting near American Elm stands
Woolly Elm Aphid - Youtube video |
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For more information about the content of this document, contact Robert Spencer.
This information published to the web on May 29, 2018.
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