Tomislav Kos ; Renata Bažok ; Darija Lemić …...Urías-López & Meinke 2001. •However results of some studies indicate that economic loss may not occur under certain conditions

Tomislav Kos(1); Renata Bažok(1); Darija Lemić(1) Jasminka Igrc Barčić(2)

(1)University of Zagreb, Faculty of Agriculture, Department of Agricultural Zoology; Svetošimunska cesta 25, 10000 Zagreb,

Croatia(2)”Chromos-Agro”, Agro-chemical Company, Radnička 173n

10000 Zagreb, Croatia

Berlin, Germany 14th – 16th

November, 2012

Maize in Croatia:

– 296.768 ha – average yield –7,0 t/ha (Statistical annual, 2011).

National average value of production 2012 = 560.891.520 €.

Average price is 27 eurocent/kg(2012).

Maize is Croatian most important arable crop.

Invasive species.

Surčin, First detection 1992, (Bača, 1994),

Bošnjaci, First detection in Croatia 1995, (Igrc Barčić and Maceljski, 1996),

Acclimatized in Pannonia valley 2001, (Dobrinčić, 2001),

First report about two independent introduction from SAD-a, (Miller et al., 2005),

Spread in 22 European countries (Edwards and Kiss, 2010).

• Why?

Depending on the year, WCR larvae are causing damages in

Croatia and in Central Europe at different

intensity level.

• Lack of investigations in Croatia and Europe!

The total damage = WCR larval population + weather conditions.

• Lack of confirmation of USA investigation.

NO threshold level for WCR

larval rootfeeding.

• Investigate how larval population and weather conditions are influencing the damage on maize.

• Investigation must be conducted in the conditions of higher populations of WCR larvae.

How to improve understanding in Croatian conditions?

Sutter at al. 1990.

• Yield loss is significantly greater if fields are infested in higher egg densities.

Urías-López & Meinke2001.

• However results of some studies indicate that economic loss may not occur under certain conditions until root ratings are much greater than 3.0 (ISU 1-6).

Oleson et al., 2005.

• The poor relationship between injury and yield most likely resulted from some locations with favorable environmental conditions that allowed the plants to compensate and prevent injury from having its maximum influence on yield.

• Overall increase of WCR population in

Croatia and in Central Europe

allow us to conduct investigation for damage forecast

under the condition of

natural WCR larval infestation !!

Economical losses in Croatian agro-

ecological conditions are recorded in

continuous maize and in first year

of sowing.

Objective:

to develop a model for damage forecast based on established WCR larval population density in the field.

Main objective

to investigate the relationship between WCR larval population which was established at the time of maximal larval attack and subsequent root damage, plant lodging and yield loss.

Specific objective

Materials and methods:

three counties; three cycles; 2006/2007,2007/2008

and 2008/2009.

1 county: 10 fields:5 continuous maize sowing.

5 first year of sowing.


• At the Julian day (JD) 170 (in 2007), 163 (in 2008) and 167 (in 2009).

• Ten plants in each of four randomly selected rows in the field were dug (i.e., 40 plants per field).

• Average number of WCR larvae per plant was assessed.

The WCR larval

population was

established in June


• At JD 203 (in 2007 and in 2009) and JD 206 (in 2008).

• Ten plants in each of four randomly selected rows in the field were dug (i.e., 40 plants per field) were dug.

• Average scores on the Node Injury Scale (NIS, 0-3) were measured.

Root ratings were

measured in June


• At the JD 261 (in 2007), 267 (in 2008) and 265 (in 2009)).

• Lodging was measured using 100 plants in 5 randomly selected rows in each field (i.e., 500 plants per field).

• The plants were grouped as follows: upright, partially and fully lodged.

Plant lodging was

estimated

in September


Partially lodged<45° Fully lodged>45°


• In each fields from each grouping, three samples containing ten plants were harvested (3x10 plants) on same JD as plant lodging.

• The average yield was determined for each category and based on the ratio of each category in a particular field.

• The average yield was calculated.

• The yield loss was calculated by comparing obtained yields with the yields of upright plants in each field.

Yield loss was

measured

in September


y = x + cycle + x : cycle

y= dependant variable;

x= independent variable.

(SAS ver. 9.1.2. (SAS Inst., 2004)).

Model for statistical analyzes between dependant and independent variables

Materials and methods:Dependent variable

Independent variable

Average number of larvae per

root;

(ANL)

Root ratings (NIS 0-

3);

(RR)

Percentage of upright plants;

100% - % Upright

plants = %Partially

lodged + % fully lodged

plants;

(Upright plants)

Percentage of partially

lodged plants;

(Partially lodged)

Percentage of fully lodged

plants.

(Fully lodged)

Yield Dry grain

(14%)

(t/ha)Root ratings (NIS 0-3);

(RR)

x

Results:

Independent

variablePr > F Cycle

Coefficient

of

regression

Number of

fields

involved in

analyze

R2

ANL 0.0006** 06/07 0.423 14

0.522ANL:CYC <.0001** 07/08 0.344 13

08/09 0.392 12

ANL vs. RR

y = 0,4229x + 0,3075R² = 0,478

y = 0,3435x + 0,8082R² = 0,0733

y = 0,3916x + 0,8543R² = 0,1024

0

0,25

0,5

0,75

1

1,25

1,5

1,75

2

2,25

2,5

2,75

3

0 0,5 1 1,5 2 2,5 3 3,5 4 4,5

Ošt

ede

nje

ko

rije

na

/ Th

ero

ot

reat

ings

(NIS

0-3

)

Prosječan broj ličinki / The average number of larvae

Regresijska analiza prosječnog broja ličinki i oštedenja korijena na kukuruzu u ponovljenoj sjetvi, 3 dvogodišnja ciklusa.

Regression analysis of the average number of larvae versus the root ratings in continuous corn for 3 two years cycles.

2006/2007 2007/2008 2008/2009

Results

According to cycle 2006/2007 at ANL of 1.08 per root the RR of 0.75 (NIS, 0-3) can be expected.

Regression analyze: ANL and RR

R2=0.522

Results:

Lack of investigations between ANL per root and RR;

Ooverlapping of different larval stages;

Mortality after larvae hatch is big and a larval development is temperature dependant;

Because of huge deviation in average monthly temperatures of soil 3rd larval stage can appear in different weeks among years.

Results:

Relationship between artificial infestation with WCR eggs and

RR

(Branson et al., 1980; Branson et al.,1982; Branson et al.,1983; Gray & Tollefson, 1987; Riedell & Schumacher, 1994; Urías-López & Meinke 2001).

Results:

Average 2 larvae per root –insecticide application (cultivation application) and additional fertilization.

Bledsoe i Obermeyer

(2010)1 larvae per root possibility of damage if we use economic threshold level of 0.75 NIS that is to some authors approximately 3.5 ISU.

Our:

Results:

4.5 to 12.7 larvae per rootcaused RR 3.3 to 4.2 (ISU 1-6) -> (NIS 0.5 – 1.0).

Artificial infestation of 1000 eggs per 30.5 cm row.

More precise approach.

Urías-López & Meinke2001 1 larvae per

root in field conditions on different level of larval and previous year adult population density (NIS 0.75).

Usually 3rd

larval or pupae stage.

Our:

Results:LODGING Independe

nt

variable

Pr > F Cycle

Coefficient

of

regression

Number

of fields

involved

in

analyze

R2

UPR

IGHT ANL 0.0002** 06-09 -16,277 37

0.336ANL:CYC

0.5428

n.s.

PARTIALLY ANL 0.0026** 06-09 12.792 37

0.349ANL:CYC

0.2902

n.s.

FULLY ANL

0.0879

n.s. n.s.

ANL:CYC0.2059

n.s.

ANL vs. Lodging

Results:

According to data from all years of investigation ANL of 1 WCR larvae per root predicts 20.4% of plant lodging. 100% - % Upright = % Partially +% Fully lodged plants

Regression analyze: ANL and upright plants

y = -16,277x + 95,831R² = 0,3356

0

10

20

30

40

50

60

70

80

90

100

0 0,5 1 1,5 2 2,5 3 3,5 4 4,5

Po

sto

tak

usp

ravn

ih b

iljak

a/

The

pe

rce

nta

ge o

f u

pri

ght

pla

nts

(%)


Regresijska analiza prosječnog broja ličinki i postotka uspravnih biljaka na kukuruzu u ponovljenoj sjetvi, 3 dvogodišnja ciklusa.

Regression analysis of the average number of larvae versus the average number of larvae in continuous corn for 3 two years cy

2006.-2009.R2=0.336

Results:

According to data from all years of investigation ANL of 1 WCR larvae per root predicts 16.5% of partially lodged

plants.

Regression analyze: ANL and partially lodged plants

y = 12,792x + 3,7091R² = 0,3487

0

10

20

30

40

50

60

70

80

90

100

0 0,5 1 1,5 2 2,5 3 3,5 4 4,5

Po

sto

tak

bilj

aka

po

legn

uti

h <

45

°o

d u

spra

vnih

/ Th

e p

erc

en

tage

of

pla

nts

lean

ing

< 4

5°

fro

m u

pri

ght

(%)


Regresijska analiza prosječnog broja ličinki i postotak biljaka polegnutih <45° od uspravnih na kukuruzu u ponovljenoj sjetvi 3 dvogodišnja ciklusa.

Regression analysis of the average number of larvae versus the percentage of plants leaning <45° from uprig

2006.-2009.R2=0.349

Results:

Plant lodging is related to June rainfalls.

no regression model.

Spike i Tollefson(1988) Opposite: Rainy

June lack of lodging.

1) deeper roots because of lack of rainfalls in May or

2) lower rate of nitrogen fertilization then Spike & Tollefson(1988) (335 kg N/ha)

Our:

Results:

Independent


Coefficient

of

regression

Number of

fields

involved in

analyze

R2

ANL 0.0286** 06-09 -944.65 370.066

ANL:CYC 0.209 n.s.

ANL vs. yield loss

Results:

According to data from all years of investigation ANL of 1 WCR larvae per root predicts 10.9% of yield loss.

Regression analyze: ANL and yield loss

y = -944,65x + 9373,4R² = 0,0665

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0 0,5 1 1,5 2 2,5 3

Pri

no

s su

ho

g zr

na

(14

%)

(t/h

a) /

Yie

ldo

fd

rygr

ain

(14

%)(

t/h

a)


Regresijska analiza prosječnog broja ličinki i gubitka prinosa na kukuruzu u ponovljenoj sjetvi, 3 dvogodišnja ciklusa.

Regression analysis of the average number of larvae versus the yield loss in continuous corn for 3 two years cycles.

2006/2007 2007/2008 2008/2009 2006-2009R2=0.066

Results:

6.5 larvae per plant caused RR 4.0±0.3 (ISU 1-6) and 16.6% as 2nd maximal yield reduction.

No regression model.

Artificial infestation of 1000 eggs per 30.5 cm row.


Urías-López & Meinke2001

1 larvae per root in field conditions on different hybrids 10.9% of yield reduction.

Usually 3rd larval or pupae stage.

Our:

Results:LODGING

Independent


Coefficient

of

regression

Number

of fields

involved

in

analyze

R2

UPR

IGHT RR 0.0002** 06/07 -26.278 15

0.529RR:CYC 0.0006** 07/08 -26.177 14

08/09 -11.185 10

PARTIALLY

RR 0.0026** 06-09 0.222 15

0.498RR:CYC

0.2902

n.s.

FULLY RR

0.0879

n.s.06-09 5.462 38

0.075RR:CYC

0.2059

n.s.

RR vs. Lodging

Results:

According to cycle 2006/2007 at RR 0.75 (NIS 0-3) 13.5% of lodged plants can be expected .

Regression analyze: RR and percentage of upright plants

R2=0.397y = -26,278x + 106,22R² = 0,529

y = -26,177x + 106,42R² = 0,617

y = -11,185x + 93,459R² = 0,1327

0

10

20

30

40

50

60

70

80

90

100

0 0,25 0,5 0,75 1 1,25 1,5 1,75 2 2,25 2,5 2,75 3

Po

sto

tak

usp

ravn

ih b

iljak

a/

The

pe

rce

nta

ge o

f u

pri

ght

pla

nts

(%)

Oštedenje korijena / The root reatings (NIS 0-3)

Regresijska analiza oštedenja korijena i postotka uspravnih biljaka na kukuruzu u ponovljenoj sjetvi, 3 dvogodišnja ciklusa.Regression analysis of the root ratings versus the percentage of upright plants in continuous corn for 3 two years cycles.

2006/2007 2007/2008 2008/2009R2=0.529

Results:

According to data from all years of investigation RR of 0.62 (NIS, 0-3) predicts 10% of partially lodged plants.

Regression analyze: RR and percentage of partially lodged plants

R2=0.397y = 19,495x - 2,0877R² = 0,4981

0

10

20

30

40

50

60

70

80

90

100

0 0,25 0,5 0,75 1 1,25 1,5 1,75 2 2,25 2,5 2,75 3

Po

sto

tak

bilj

aka

po

legn

uti

h <

45

°o

d u

spra

vnih

/ Th

e p

erc

en

tage

of

pla

nts

lean

ing

< 4

5°

fro

m u

pri

ght

(%)

Oštedenje korijena / The root ratings (NIS 0-3)

Regresijska analiza oštedenja korijena i postotak biljaka polegnutih <45° od uspravnih na kukuruzu u ponovljenoj sjetvi 3 dvogodišnja ciklusa.

Regression analysis of the root ratings versus the percentage of plants leaning <45° from upright in continuous c

2006.-2009.R2=0.498

Results

According to data from all years of investigation RR of 2.14 (NIS, 0-3) predicts 10% of fully lodged plants.

Regression analyze: RR and percentage of fully lodged plants

y = 5,4624x - 1,6897R² = 0,1754

0

5

10

15

20

25

30

35

40

1 1,2 1,4 1,6 1,8 2 2,2 2,4 2,6

Po

sto

tak

bilj

aka

po

legn

uti

h >

45

°o

d u

spra

vnih

/ Th

e p

erc

en

tage

of

pla

nts

lean

ing

> 4

5°

the

n u

pri

ght

(%)

Oštedenje korijena / The root ratings (ISU 1-6)

Regresijska analiza oštedenja korijena i postotak biljaka polegnutih >45° od uspravnih na kukuruzu u ponovljenoj sjetvi, 3 dvogodišnja ciklusa.

Regression analysis of the root ratings versus the percentage of plants leaning > 45° then upright in continuous

2006.-2009. Linear (2006.-2009.)R2=0.075

Results:

Highly significant correlation were present between infestation and root damage rating r=0.710**.

RR 7.0 scale (1-9) -> 16.5% plant lodging.

Riedell andSchumacher

(1994)

14.0% at 0.75 (NIS 0-3).

Similar but with regresionmodel.

Our:

Results:

Climatic conditions in each year influence on lodging.

Coefficient of determination depend on environmental stress that affect on plants.

Coefficient of determination is higher if environmental stress is heavier.

Olesonet al. 2005.

Environmental stress

RR (NIS 0-3) / 10% Lodged

plantsR2 Our R2

High 0,02 0.70

Medium 1.07 0.46 0.62 0.498

low 1.03 0.28

Results:

Independent


Coefficient

of

regression

Number of

fields

involved in

analyze

R2

RR 0.0006** 06/07 -2299.17 38

0.157RR:CYC

0,2098

n.s.

RR vs. yield loss

Results:

According to data from all years of investigation RR of 0.75 (NIS 0-3) predicts 17.5% of yield loss.

Regression analyze: RR and yield loss

y = -2299,1x + 9853,6R² = 0,1576

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

0 0,25 0,5 0,75 1 1,25 1,5 1,75 2 2,25 2,5 2,75 3

Pri

no

s su

ho

g zr

na

(14

%)

(t/h

a) /

Yie

ldo

fd

rygr

ain

(14

%)(

t/h

a)

Oštedenje korijena / The root ratings (NIS 0-3)

Regresijska analiza oštedenja korijena i prosječnog prinosa po biljci na kukuruzu u ponovljenoj sjetvi, 3 dvogodišnja ciklusa.Regression analysis of the root ratings versus the average yield per plant in continuous corn for 3 two years cycles.

2006.-2009.R2=0.158

Results:

At RR 3.5 (ISU 1-6) -> 11.82% yield reduction.

GLM regression model R2=0.29.

A yield lossof separate plant.

Branson et al., 1980. At RR of 0.75

(NIS 0-3) 17.5% of estimated field yield loss on different hybrids.


Our:

Results:

At RR 3.5±0.3 (ISU 1-6) 17.1% as maximal yield reduction.

No regression model.

Artificial infestation of 1000 eggs per 30.5 cm row omome hybrid.


Urías-López & Meinke2001

At RR of 0.75(NIS 0-3) 17.5% of yield loss different hybrids.


Our:

Results:

Coefficient of determination of model depend on environmental stress that affect on plants.

Coefficient of determination is higher if environmental stress is higher.

Olesonet al. 2005.

Environmental stress

RR (NIS 0.75) /

Yield loss

Model R2 Our Model R2

High 85% Exponencial 0.686

Medium 6.51% GLM 0.076 17.5% GLM 0.158

Low 0.24% GLM 0.001

Conclusions:

The relationship between WCR larval feeding and yield loss is difficult to quantify by model. We have to agree with Spike

and Tollefson (1991) that a clearer understanding of secondary factors may provide insight into more effective

management of both the insect and the crop.

Efficacy of damage forecast is determinate with influence of agro-ecological factors on development of pest (WCR) and

maize (host).

Conclusions:

Damage forecast according ANL as a tool could be easier and faster and more acceptable for farmers (practice).

Because it consumes less time than RR and does not depend on higher level of knowledge needed for RR.

Lack of this tool is necessity for calculating degree day for 3rd larval stage, and possibility to fail in establishing peak of population.

Forecasting of root damage by ANL per root in field conditions is possible but depends on weather

conditions.

Forecasting damage expressed as lodged plants and yield loss by RR as a tool is better than by ANL per

plant.

Acknowledgements:

Especially thanks to farmers who gave their fields for observations even they handle serious damage.

• Risk estimation system - the basis for integrated control of corn pests (Ministry of Science, Education and Sport; number: 178-1782066-2064), Project leader Prof. Renata Bažok, PhD.

Developing IPM in maize through WCR risk management- FAO Project GTFS/RER/017/ITA, Project leader prof. Jasminka Igrc Barčić, PhD.

• Helpers in the field: Students Antonela Kozina DamirBertić.

Thanks for attention !

Documents

Tomislav Kos ; Renata Bažok ; Darija Lemić …...Urías-López & Meinke 2001. •However results of some studies indicate that economic loss may not occur under certain conditions