acorn infestation rates in quercus - silvo ......acorn infestation rates in quercus long-term field...
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ACORN INFESTATION RATES
IN QUERCUS
LONG-TERM FIELD MONITORING IN AN
IBERIAN DEHESA AND WIDESCALE
META-ANALYSES.
TARA CANELO HERNÁNDEZ
RAÚL BONAL ANDRÉS
Oak trees
Quercus spp.ACORNS
Livestock feeding
autumn-winter
PESTS
Curculio spp. weevils Cydia spp. moths
DEHESAS AND MONTADOS
BIOLOGICAL CYCLE
ADULT
ACORN
LARVA
EGG
SOIL
LARVAADULT
ADULT
ACORN
LARVA
EGG
LARVAADULT
LARVA
STUDIES
Rates of infestation
Total number of acorns
TOTAL 23 studies 72 data
CURCULIO 20 studies
CYDIA 17 studies
QUESTIONS
1) Which is the main acorns pest?
2) Do the stimations of infestation rates depend on the
sampling methods?
3) Which environmental variables influence acorns
infestation rates?
INFESTATION RATES
Global infestation rate
Cydia spp. 0.1309
Curculio spp. 0.2719
Curculio
27,19%
Cydia
13,09%
Is it actually higher the rate of weevil infestation?
H0: there are not differences between Cydia and Curculio rates.
H1: there are differences.
Repeated measures ANOVA
YES
(p<0,0001)
INFESTATION RATES
What is affecting infestation
rates?
agrifolia alba cerris engelmannii ilex mongolica robur rubra serrata suber suber
0.0
0.2
0.4
0.6
Quercus
Ra
te o
f C
urc
ulio
Rate of Curculio - Quercus
Rate of Cydia - Quercus
agrifolia alba cerris engelmannii ilex mongolica robur suber
0.0
0.1
0.2
0.3
0.4
0.5
Quercus
Ra
te o
f C
yd
ia
SAMPLING
METHODOLOGY
SEED TRAPS GROUND
Ground Traps
0.0
0.1
0.2
0.3
0.4
0.5
SamplingR
ate
of C
yd
ia
Rate of Curculio Rate of Cydia
Ground Traps
0.0
0.2
0.4
0.6
Sampling
Ra
te o
f C
urc
ulio
METHODOLOGY
INFESTATION RATES
Quercus
Year
Methodology
Latitude
META-ANALYSIS
EFFECT SIZES
Effect size is a name given to a family of indices
that measure the magnitude of a treatment
effect.
These indices are independent of sample size.
TOTAL NUMBER OF ACORNS
META-ANALYSIS
Quercus ilex
This model explains 52,68 % variabilityModel: Effect Size ~ Quercus
AIC: 246.95
Curculio
This model explains 99,06 % variabilityModel: Effect Size ~ Sampling
AIC: 275,64
Cydia
This model explains 95,97 % variabilityModel: Effect Size ~ Sampling
AIC: 124,67
Curculio
This model explains 98,66 % variabilityModel: Effect Size ~ Sampling
AIC: 152,66
Cydia
What environmental variables influence acorns infestation rates?
Iberian dehesa
6 years
(2008-2013)
25 trees
Mixed Effects Logistic Regression
What determines the rate of weevil infestation?
The total number of adults that climb the tree and the amount of acorns produced by the tree
(p < 0,0001)(p < 0,0001)
PREDATOR SATIATION
What influences adult numbers?
The greater the total amount of rainfall during the emergency period, the
greater the total number of adults.
The timing of late summer storms determines the timing of adult
emergence.
the later the rains the later weevils emerge
What happens in the case of Cydia?
Not dependent on rainfall
Infestation rates by Cydia only depend on the total
amount of acorns
ADULT
ACORN
LARVA
EGG
LARVAADULT
PREDATOR SATIATION
CONCLUSIONS
1) Curculio spp. are the main acorns pest.
2) Infestation rates vary a great extent between Quercus species.
3) The sampling method has an effect on the estimation of infestation rates:
collecting acorns from the ground may underestimate them.
4) Inter-annual variability of acorns infestation rates by Curculio depend not only
on acorn crop size, but also on the amount of rainfall during the adult
emergence period.
5) Long summer droughts are not good for acorn productions…
but at least, the lack of rain also kills the weevils!!!
THANKS FOR YOUR ATTENTION