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Insect of the Month - Cottony Ash Psyllid | |
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Hort Snacks - November 2018 | |
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| Causal Organism: Psyllopsis discrepans
Crops Affected: Select Ash tree species (black, mancana, manchurian, hybrids of black/Manchurian ash, etc.) – not green or white ash
Life Cycle:
- Aphid-like insect that feeds by piercing and sucking, injecting saliva into the leaf
- Adults are small (~3mm in length), light green to light yellow with black markings and mostly clear wings (shaded towards tips)
- At least 2 generations are present each year
- Eggs overwinter in tight bends (crotches) between twigs and buds
- Eggs hatch around the time of bud break
- 2nd generation eggs are laid along the top of the midrib of the leaves
- Nymphs feed on expanding leaves
- Nymphs exude a white, waxy substance, leading to the characteristic appearance of “cotton”
- 2nd generation nymphs feed within the curled/deformed leaves and on other, unaffected leaves
Symptoms:
- Feeding by nymphs causes leaflets to curl along the edge and be deformed – most obvious symptom
- Leaflets roll under and curl towards the midrib of the leaf
- Leaflets of ash trees may show browning or yellowing in addition to curling
- Severe curling is referred to as “cauliflower” appearance
- White, cottony material may be observed along the midrib of an uncurled leaf
- Tree crown may appear thinner over time
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Cottony ash psyllid adult | Curled / distorted leaves caused by Cottony ash psyllid nymphal feeding |
Photo by City of Saskatoon | Photo by City of Edmonton | Photo by City of Saskatoon |
Monitoring:
- Monitor trees early for 1st generation nymphal feeding (to allow treatment) and throughout the summer for 2nd generation damage
- Watch for curling and for cottony material
Management:
- Ensure that trees are kept healthy – ensure good drainage, adequate water and nutrients and freedom from compaction, crowding or other stresses
- Some literature suggests that watering trees can help to minimize observed damage in trees
- Control weeds at the base of trees to reduce competition for moisture
- Bark mulch or other materials can reduce water requirement
- Control products available for treating trees are limited, particularly in urban and residential situations
- Some domestic products (e.g. insecticidal soaps) are registered and can be used for control of the pest
- Treat plants shortly after bud break as the eggs are hatching
- Treatment later stages (particularly with contact-type products) will be less effective
- Systemic products are effective but are restricted and not available to everyone
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For more information about the content of this document, contact Robert Spencer.
This information published to the web on October 30, 2018.
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