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 37.8 0C. 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 excerptalis Walker), 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 Egg mass

TSB Moth TSB Larva

TSB infested cane 100 88.66% 86.20% 80

60 58.24% 46.33% 40 37.00% 30.23% 20 16.53% TSB infestation (%) infestation TSB 13.26% 0 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 Year

Figure 1 Top shoot borer infestation in different years SB moth Egg mass

SB infested cane Larvae feeding inside cane 90 84.0% 80 70 60 50 40.09% 40 33.18% 30 26.99% 29.30% 20.77% 20 SB infestation (%) infestation SB 10 10.40% 7.30% 0 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 Year

Figure 2 Stem borer infestation in different years RSB moth RSB larva

RSB infested cane Injured stock 50 44.57% 40

29.98% 30 27.42%

20 19.62% 12.57% 10 10.03 RSB infestation (%) infestation RSB 0 4.12% 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 Year

Figure 3 Rootstock borer infestation in different years March max. 40.00 min. 0 35.00 35.19 C 30.00 29.40 0C 25.00 20.90 0C 20.00 15.00 16.15 0C 10.00 Temperature(˚c) 5.00 0.00 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 year

Figure 4 Average maximum and minimum temperature in March (28 years) April max. 45.00 min. 40.00 39.76 0C 35.00 30.00 30.12 0C 25.00 25.43 0C 20.00 20.40 0C 15.00 10.00 Temperature(˚c) 5.00 0.00 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 year

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

40.00 37.97 0C min. 35.00 30.00 31.63 0C 26.11 0C 25.00 20.00 23.28 0C 15.00 10.00 Temperature(˚c) 5.00 0.00 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 year

Figure 6 Average maximum and minimum temperature in May (28 years) June max. 40.00 min. 35.72 0C 35.00 31.30 0C 30.00 27.07 0C 25.00 24.52 0C 20.00 15.00 10.00 Temperature(˚c) 5.00 0.00 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 year

Figure 7 Average maximum and minimum temperature in June (28 years) July max. 40.00 min. 0 35.00 34.53 C 30.00 31.02 0C 25.00 26.86 0C 25.50 0C 20.00 15.00 10.00 Temperature(˚c) 5.00 0.00 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 year

Figure 8 Average maximum and minimum temperature in July (28 years) August max. 40.00 min. 35.00 34.40 0C 31.32 0C 30.00 27.15 0C 25.00 25.74 0C 20.00 15.00 10.00 Temperature(˚c) 5.00 0.00 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 year

Figure 9 Average maximum and minimum temperature in August (28 years) September max. 40.00 min. 35.00 34.06 0C 30.00 31.13 0C 26.97 0C 25.00 24.75 0C 20.00 15.00 10.00 Temperature(˚c) 5.00 0.00 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 year

Figure 10 Average maximum and minimum temperature in September (28 years) October max. 40.00 min. 0 35.00 35.29 C 30.00 0 29.71 0C 25.00 25.24 C 20.00 21.92 0C 15.00 10.00 Temperature(˚c) 5.00 0.00 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 year

Figure 11 Average maximum and minimum temperature in October (28 years) 40.00 Max.temp Min.temp 35.59 0C 35.00 31.84 0C 30.00

25.00 26.41 0C

20.00 18.56 0C 15.00 July May April June March August October September

Figure 12 Month-wise average maximum and minimum temperature (28 years) R.humidity(%) 95.00 89.81% 90.00 85.00 86.32% 80.00 75.00 70.00 74.33% 65.00 60.00 55.00 50.00 45.00 July May April June March August October September

Figure 13 Month-wise average relative humidity (28 years) Rainfall (mm) 8600.00 7582.03 7713.05 7600.00 6600.00 6456.80 5600.00 6125.52 4600.00 5108.53 3600.00 2600.00 3495.96 1902.25 1600.00 600.00 928.75 July May April June March August October September

Figure 14 Month-wise total rainfall (28 years) Table 1: Correlation (r) of climatic factors with borer incidence Month Climatic factors Top shoot borer Stem borer Rootstock borer May Av. Max. temp.( ˚c) 0.034 0.179 0.525** Av. Min. temp.( ˚c) 0.154 -0.091 0.114 Av. R. humidity (%) -0.022 0.081 -0.263 Total Rainfall (mm.) 0.149 0.038 -0.563** June Av. Max. temp.( ˚c) -0.225 -0.009 0.300 Av. Min. temp.( ˚c) 0.011 -0.105 0.138 Av. R. humidity (%) -0.059 0.014 -0.108 Total Rainfall (mm.) 0.448* 0.139 -0.254 July Av. Max. temp.( ˚c) -0.309 0.399* 0.223 Av. Min. temp.( ˚c) -0.264 0.160 -0.006 Av. R. humidity (%) -0.256 -0.299 -0.054 Total Rainfall (mm.) 0.052 -0.369 0.002 August Av. Max. temp.( ˚c) -0.241 -0.053 0.276 Av. Min. temp.( ˚c) -0.209 -0.156 0.084 Av. R. humidity (%) -0.177 0.134 -0.238 Total Rainfall (mm.) 0.180 -0.080 -0.240 September Av. Max. temp.( ˚c) 0.038 0.221 0.354 Av. Min. temp.( ˚c) -0.225 -0.204 0.192 Av. R. humidity (%) -0.264 0.008 -0.349 Total Rainfall (mm.) -0.006 -0.344 -0.380* October Av. Max. temp.( ˚c) 0.009 0.089 0.075 Av. Min. temp.( ˚c) -0.228 -0.379* -0.154 Av. R. humidity (%) -0.259 -0.099 -0.201 Total Rainfall (mm.) -0.117 -0.200 0.001 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 Swinhoe was 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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