The behaviour and
lifecycle of pear bud
weevil (Anthonomus
piri) and potential for
control.
Michelle Fountain, Maddie
Cannon, Adrian Harris
Anthonumus
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rubi - strawberry
eugenii - pepper
grandis - cotton
pomorum - apple
piri – pear
• Buds and flowers
Anthonomus piri
• Commonly known as apple bud weevil
• Adult weevils lay eggs in the
overwintering buds, in the autumn
• Hatch into larvae feeding on the inside
of the bud
• Pupating and emerge in the spring as
adults (Alford, 2007)
• Female weevil can lay up to 25 eggs
– E.g. loss of 25 clusters of pears per female
weevil
– significant loss of yield to pear growers
Why becoming a problem?
• Anthonomus piri increasingly damaging pest in pear orchards
• Pear sucker resistance to insecticides - reduced use of insecticides
in pear orchards with a higher reliance on natural enemies
• Earwigs are important predators of many orchard pests
• Anthocorids are also important predators of pear sucker
• TF 196 and TF 220 projects at NIAB EMR
• acetamiprid (Gazelle) less harmful to earwigs than
• thiacloprid (Calypso) in lab studies
•
Peusens and Gobin (2008), Vogt et al (2010) and Shaw and Wallis (2010)
• Effects of field sprays in apple orchards were negligible
Biology and control
• Activity
– Day/night
• Fecundity
• Acetamiprid and thiacloprid efficacy for
control?
– Generally applied in autumn
– Harvest Intervals and natural enemies
Activity in spring
• Tap sampling in
Conference pear orchard
• Transect walked diagonally
across the orchard on
each visit
• 30 trees, beating one
branch on each tree 3
times with a stick over a
white tray
• Feb / Mar
• Day / night
Activity
Tap sampling 30 pear trees and night and in the day for pear bud weevil
2 Mar
3 Mar
4 Mar
Day
Night
Day
Night
Day
Night
Temp
4-8oC
4-8oC
4-10oC
4-10oC
0-10oC
0-10oC
Weather
Very windy
Very windy
Breeze
Breeze
Breeze
Breeze
Notes
Legs folded Legs folded Walking Walking Legs folded
Legs folded
Tree
16:30
19:00
15:30
19:00
12:20
19:10
TOTAL
1
3
0
14
0
9
• Night activity in spring
• Identification high variation between
individuals – dark
• Centipedes, spiders and earwigs springtails and woodlice
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2 March – low numbers of weevils
17 March 10 weevils collected
5 male and 5 were female
Mating observed
Females contained eggs
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30 March - 1 weevil on 60 trees
25 buds - 5 weevil feeding damage
Eggs laid just under the scale
Feeding damage appeared to go into the
centre of the flower bud
Grower field spray trial
• A small unreplicated spray trial
• Four rows to east of the orchard
unsprayed
• Rest of the orchard sprayed with
Calypso (thiacloprid) at the label
rate by the grower on 9 March
• Assessed on the evening 14
March
• Tap sampling 30 trees on each
side
• 9 weevils – untreated
• Observed mating
• 7 on thiacloprid side
• 6 moribund with legs curled under the body
• Dead within 2 days
Laboratory spray experiment
• Treatments acetamiprid or thiacloprid at full
or half field rate
Product
Field dosage
Recommended
Field spray
Field
field spray
volume (L/ha)
concentration
volume (L/ha)
Control
Water
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Acetamiprid Gazelle
375 g/ha
500-1500
1000
0.375 g/l
Thiacloprid
375 ml/ha
1000-1500
1000
0.375 ml/l
Acetamiprid Gazelle
187.5 g/ha
500-1500
1000
0.1875 g/l
Thiacloprid
187.5 ml/ha
1000-1500
1000
0.1875 ml/l
Calypso
Calypso
• Weevils collected from commercial pear orchard - 29
March 2016
• 30 March transferred into 5 cm petri dishes
• Filter paper disk at bottom
• Burkard computer controlled sprayer
• Transferred to clean dishes (honey wet/paper) at 16 oC
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10 replicates
Assessed at 0, 1.5, 16, 24, 96, 192 and 264 h (11 d)
Frozen and dissected, gender identified
Females distinctive spermatheca
Males - penis
Laboratory spray experiment
• 11 days post application
• NSD between males and females
Laboratory spray experiment
Conclusions
• Pear bud weevil night active and mating on warmer
evenings in the spring - Monitoring
• Females are laying eff in flower buds at this time
• Uncertainty over the lifecycle in UK pear orchards
• Further studies needed on lifecycle and activity
• Control: Preliminary studies
– Gazelle not effective
– Calypso up to 90% efficacy in lab
• Pilot study giving a best case scenario
• WARNING – do not treat every orchard - monitor
• Repeated with further replicated trials in pear orchards
Thanks
• Nigel Jenner (Avalon)
• David Long
• Jim Gunyan
• Adrian Harris (NIAB EMR)