Title :

Influence of Climatic Changes on the Abundance of Major Insect Pests of

Sugarcane

Presented by

M. Abdullah

Bangladesh Sugarcane Research Institute

Ishurdi, Pabna, Bangladesh

INTRODUCTION

Agriculture is strongly interrelated with climatic factors. Temperature, which is one of the main factors of climate, is closely associated with agricultural production. Global warming is the increase in the average temperature of the Earth’s atmosphere and oceans that has been observed in recent decades.

The tropical and subtropical countries are more vulnerable to the potential impact of global warming through the effects on crops,soils, insects, weeds, and diseases.

Bangladesh is in the subtropical region. Therefore, the agriculture of this country may be affected.

Climate change may lead to an increase in world hunger unless population growth rates in developing nations are much smaller than currently projected, and farmers obtain adequate assistance.

It is expected that due to climate change, humidity, wind flow, and temperature in Bangladesh may be changed. These three climatic mechanisms, in changing conditions, cause an increase in insect pests, diseases and microorganisms in agriculture, and accordingly, crop production may be decreased.

These changes may increase the frequency and intensity of extreme weather events, such as tropical cyclones or floods.

Temperature has been considered as the most dominant factor of environment, influencing the development, survival, feeding, fecundity, dispersal, distribution and abundance of insects. Insects generally grow rapidly in warmer conditions.

It seems obvious that any significant change in climate on a global scale influence local agriculture, and therefore, affect the world's food supply.

So far about 70 species of insect pests have been identified in Bangladesh of which the most damaging are top shoot borer, stem borer and rootstock borer.

Among various factors, insect pests inflict considerable losses which are estimated to be around 20% in cane yield and 15% in sugar recovery (Avasthy, 1983).

►10% infestation by top shoot borer caused 12.29% yield loss and 80% infestation caused 35.01% yield loss (Alam et al.,2006).

► 10% infestation by stem borer caused 12.01% yield loss and 80% infestation caused 27.81% yield loss (Alam et al., 2006).

► 10% infestation by rootstock borer caused 10.44% yield loss and 60% infestation caused 27.76% yield loss (Alam et al., 2006).

► Stem borer caused 28.73% yield loss and 15.93% recovery loss (Abdullah et al., 2006)

Gupta (1956) reported that low maximum temperature is generally

considered favourable for build-up of top shoot borer. Gupta (1959)

has deduced it to be below 37.80C. The optimum relative humidity

for borer activity varies 60-80% (Singh, et al., 1957; Gupta, 1959).

High rainfall is also regarded as a contributory factor for profuse

multiplication of the borer (Gupta, 1959).

Rainfall appears to favour stem borer multiplication. However, under

drought conditions, profuse egg laying take place in July. High

atmospheric humidity during August also favour rapid build-up of the

borer (Gupta and Avasthy, 1957). The incidence of the pest is

significantly high in heavy soils and under water logged and flooded

conditions (Khanna et al., 1957).

The root borer has been observed to be active at high temperature

and moderate humidity levels and appears to be tolerant to rain to

an extent of 45cm after which its population declines (Gupta, 1953).

Root borer incidence and population are generally high in unirrigated

fields and in sand or sandy loam soils (Gupta and Avasthy, 1952).

Therefore, an investigation was made to observe the effect of

climatic factors on the abundance of major insect pests in

sugarcane.

MATERIALS AND METHODS

The investigation was made at Bangladesh Sugarcane Research Institute (BSRI), Ishurdi from 1980 to 2007. Planted sugarcane varieties/clones were subjected to natural infestation. No pest control measure was applied.

Data on the incidence of top shoot borer (Scirpophaga excerptalisWalker), stem borer (Chilo tumidicostalis Hampson) and rootstock borer (Emmalocera depressella Swinhoe) were taken from March to October. The percentage of infestation was calculated by counting the total and infested canes. Data on climatic factors viz., maximum temperature, minimum temperature, relative humidity (%) and rainfall were recorded by biometry section of the institute. Correlations of climatic factors with borer infestation were calculated.

Growth rate of temperature and pest infestation is calculated by using Discrete formula:Growth Rate r : ((A/P)1/t -1), where P= Value of the variable at beginning of period, A= Value of the variable at end of period, t= Number of periods including first and last.Growth rate is also calculated using Microsoft Excel: ((((A/P)^(1/t))*100

RESULTS & DISCUSSION

TSB Moth

Egg mass

TSB Larva

TSB infested cane

0

20

40

60

80

100

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

TS

B in

fest

atio

n (%

)

Figure 1 Top shoot borer infestation in different years

88.66% 86.20%

13.26%

37.00%

58.24%

16.53%

30.23%

46.33%

SB mothEgg mass

SB infested cane Larvae feeding inside cane

0102030405060708090

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

SB

infe

stat

ion

(%)

Figure 2 Stem borer infestation in different years

84.0%

26.99%

40.09%

29.30%33.18%

10.40% 7.30%

20.77%

RSB moth RSB larva

RSB infested caneInjured stock

0

10

20

30

40

50

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Year

RS

B in

fest

atio

n (%

)

Figure 3 Rootstock borer infestation in different years

19.62%

27.42%

12.57%

10.03

4.12%

29.98%

44.57%

March

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

Tem

pera

ture

(˚c)

max.

min.

Figure 4 Average maximum and minimum temperature in March (28 years)

35.190C

29.400C

20.900C

16.150C

April

0.005.00

10.0015.0020.0025.0030.0035.0040.0045.00

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

Tem

pera

ture

(˚c)

max.

min.

Figure 5 Average maximum and minimum temperature in April (28 years)

39.760C

30.120C25.430C

20.400C

May

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

Tem

pera

ture

(̊c)

max.

min.

Figure 6 Average maximum and minimum temperature in May (28 years)

37.970C

31.630C26.110C

23.280C

June

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

Tem

pera

ture

(̊c)

max.

min.

Figure 7 Average maximum and minimum temperature in June (28 years)

31.300C

35.720C

24.520C

27.070C

July

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

Tem

pera

ture

(˚c)

max.

min.

Figure 8 Average maximum and minimum temperature in July (28 years)

34.530C

31.020C

26.860C 25.500C

August

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

Tem

pera

ture

(̊c)

max.

min.

Figure 9 Average maximum and minimum temperature in August (28 years)

34.400C

31.320C 27.150C25.740C

September

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

Tem

pera

ture

(̊c)

max.

min.

Figure 10 Average maximum and minimum temperature in September (28 years)

34.060C

31.130C26.970C

24.750C

October

0.005.00

10.0015.0020.00

25.0030.0035.0040.00

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

year

Tem

pera

ture

(˚c)

max.

min.

Figure 11 Average maximum and minimum temperature in October (28 years)

35.290C

29.710C25.240C

21.920C

15.00

20.00

25.00

30.00

35.00

40.00

Mar

ch

Apr

il

May

June

July

Aug

ust

Sep

tem

ber

Oct

ober

Max.temp

Min.temp

Figure 12 Month-wise average maximum and minimum temperature (28 years)

35.590C

31.840C

26.410C

18.560C

R.humidity(%)

45.0050.0055.0060.0065.0070.0075.0080.0085.0090.0095.00

Mar

ch

Apr

il

May

June

July

Aug

ust

Sep

tem

ber

Oct

ober

Figure 13 Month-wise average relative humidity (28 years)

89.81%

74.33%

86.32%

Rainfall (mm)

600.00

1600.00

2600.00

3600.00

4600.00

5600.00

6600.00

7600.00

8600.00

Mar

ch

Apr

il

May

June

July

Aug

ust

Sep

tem

ber

Oct

ober

Figure 14 Month-wise total rainfall (28 years)

928.75

1902.25

5108.53

6456.80

7582.03

6125.52

7713.05

3495.96

0.001-0.201-0.154

0.075-0.380*-0.3490.192

0.354-0.240-0.2380.084

0.2760.002-0.054-0.006

0.223-0.254-0.1080.138

0.300-0.563**-0.2630.114

0.525**

Rootstock borer

-0.200-0.099-0.379*

0.089-0.3440.008-0.204

0.221-0.0800.134-0.156

-0.053-0.369-0.2990.160

0.399*0.1390.014-0.105

-0.0090.0380.081-0.091

0.179

Stem borer

-0.117-0.259-0.228

0.009-0.006-0.264-0.225

0.0380.180-0.177-0.209

-0.2410.052-0.256-0.264

-0.3090.448*-0.0590.011

-0.2250.149-0.0220.154

0.034

Top shoot borer

Total Rainfall (mm.)Av. R. humidity (%)Av. Min. temp.( ˚c)

Av. Max. temp.( ˚c)Total Rainfall (mm.)Av. R. humidity (%)Av. Min. temp.( ˚c)

Av. Max. temp.( ˚c)Total Rainfall (mm.)Av. R. humidity (%)Av. Min. temp.( ˚c)

Av. Max. temp.( ˚c)Total Rainfall (mm.)Av. R. humidity (%)Av. Min. temp.( ˚c)

Av. Max. temp.( ˚c)Total Rainfall (mm.)Av. R. humidity (%)Av. Min. temp.( ˚c)

Av. Max. temp.( ˚c)Total Rainfall (mm.)Av. R. humidity (%)Av. Min. temp.( ˚c)

Av. Max. temp.( ˚c)

Climatic factors

October

September

August

July

June

May

Month

Table 1: Correlation (r) of climatic factors with b orer incidence

5% 1% Tabulated r' 0.374 0.479 df = 26

CONCLUSION

► The abundance of top shoot borer, Scirpophaga excerptalis Walker was positively correlated with rainfall (r = 0.448*) in the month of June where temperature and humidity did not affect significantly on their incidence.

► Stem borer, Chilo tumidicostalis Hampson was found positively correlated with average maximum temperature in July (r = 0.399*) and negatively correlated with average minimum temperature in October (r = -0.379*) where humidity and rainfall did not affect significantly on their incidence.

► The abundance of rootstock borer, Emmalocera depressella Swinhoewas positively correlated with average maximum temperature (r = 0.525**) and negatively correlated with rainfall in the month of May (r = -0.563**) and September (r = -0.380*).

► Top shoot borer and rootstock borer infestation were increased by 2.09% and 1.43% respectively during the last 28 years.

► Maximum and minimum temperature was increased by 0.18% and 0.22% respectively in the month of May during the last 28 years.

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