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