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Climate change and its Impact on Insect Pest
- 1. Changing Climate and its Impact on Insect Pest Research Scholar Ms. Pushpa Singh (PZ-12036) Department of Entomology and Agricultural Zoology Institute of Agricultural Sciences BHU, Varanasi – 221 005 Course Seminar on
- 2. Overview of presentation •Introduction •Causes for Climate Change •Present and future trends of CO2 •Effect of elevated CO2 on host plants and insects •Effect of temperature on host plants and insects •Precipitation/rainfall. •Impact of climate change on IPM •Conclusion
- 3. Introduction contd… Carbon dioxide (CO2) • The atmospheric conc. of CO2 in 2005 - 379 ppm Preindustrial levels – 280 ppm • Currently – 380 ppm • By the end of this century – 560 ppm Temperature • Temperature increased by 0.740oC in 20th century • Sea level raised by 17 cms. • Increase by 1.4 – 6.4oC by the end of this century • Increase in the frequency, intensity and duration of floods, droughts and heat waves. IPCC,2007
- 4. Precipitation • Increased significantly in eastern parts of North and South America, northern Europe and northern and central Asia, • Declined in the Sahel, the Mediterranean, southern Africa and parts of south Asia
- 5. Causes of Climate Change Natural Causes Continental drift Volcanoes The earth's tilt Ocean currents Anthropogenic Causes large-scale use of fossil fuels for industrial activities Greenhouse gases and their sources our daily lives contribute our bit to this change in the climate (http//:edugreen.teri.in/explore/climate)
- 6. Possible Effects of Climate Change • Increase in frequency of hot extremes, heat waves and heavy precipitation. • Increase in tropical cyclone intensity. • Decrease in water resources in many semi-arid areas, such as the Mediterranean Basin, western United States, southern Africa and north-eastern Brazil. • Possible elimination of the Greenland ice sheet and a resulting contribution to sea level rise of about 7 metres. •Possible disappearance of sea ice – end of 21st century. • 20 to 30% of species assessed increased risk of extinction if warming exceed 1.5 to 2.5 degrees. (Pachauri, 2008)
- 7. Increase Monsoon Rainfall: West coast, North A. P. and North-west India. Decrease Monsoon Rainfall: East M. P. and adjoining areas, North-east India and parts of Gujarat and Kerala. Increase in Temp.: West coast, Central India, and Interior Peninsula and over Northeast India. Decrease in Temp.:Northwest and some parts in Southern India. Glaciers in Himalayas are receding at a rapid pace. Indian Scenario of Climate Change
- 8. Predicted effect of climate change on Agriculture over the next 50 years Climate element Expected change by 2050 Confidence in prediction Effect on agriculture CO2 Increase from 360 PPM to 450 – 600 PPM Very high Good for crops Increased photosynthesis Reduced water use Sea level rise Rise by 10-15cm Very high Loss of land Coastal erosion Flooding Salinization of ground water. Temperature Rise by 1-2 OC Increased frequency of heat waves High shorter growing seasons Heat stress risk Increased Evapotranspiration Precipitation Seasonal changes by + or – 10% Low •Drought •Soil problem •Water logging Storminess Increased wind speeds, more intense rainfall events Very high Lodging Soil erosion Reduced infiltration of rainfall IPCC 2001
- 9. Projected Impacts on Indian agriculture Increase in CO2 to 550 ppm increases yields of rice, wheat, legumes and oilseeds by 10-20%. 10C increase in temperature may reduce yields of wheat, soybean, mustard, groundnut, and potato by 3-7%. Much higher losses at higher temperatures. Productivity of most crops to decrease only marginally by 2020 but by 10-40% by 2100. Possibly some improvement in yields of chickpea, rabi maize, sorghum and millets; and coconut in west coast. Less loss in potato, mustard and vegetables in north-western India due to reduced frost damage.
- 10. Need of studying climate change effect on insect Insects are the numerous form of animal on the planet with one million insect species described. Close to 80% of all animal species, human have described are insects. Insects are the most important from the point of 1.ecosystem functioning(energy recycling) 2. economically important crop pests vectors pollinators productive
- 11. In 1750 level of CO2 in Atmosphere was 280ppm Safe level of CO2 in Atmosphere is, 300-350 ppm In 1750 level of CO2 in Atmosphere was 280ppm Safe level of CO2 in Atmosphere is, 300-350 ppm 385.99 ppm Atmospheric CO2 for November 2009 NOAA,2009)
- 12. How enriched CO2 benefits to C3 Plants than C4 ? Showed excess CO2 gave a 35% photosynthesis boost to rice and 32% boost to soybeans (both C3 plants), but only a 4% boost to C4 crops Cure and Acock, 1986
- 13. With rising CO2 levels……. C3 plant species continue to increase photosynthesis C4 plants do not. C3 plants can respond readily to higher Co2 level C4 plants can make only limited response Impact of Elevated CO2 on Plants….. Increase: Photosynthesis Above ground biomass Increases the carbon to nitrogen ratio of plant tissues Ainsworth etal. (2002) Reducing the nutritional quality especially nitrogen Coviella et al. (1999)
- 14. Herbivores…. Increase: Food consumption Developmental time Reducing: Growth rates Food conversion efficiency Watt et al.1995.
- 15. Effect of Elevated carbon on plants and hervivoresT Cornelissen
- 16. How elevated CO2 affect insect-plant interaction? By increasing References Food consumption by caterpillars Osbrink et al. (1987) Reproduction of aphids Bezemer et al. (1999) Predation by lady beetle Chen et al. (2005)
- 17. By decreasing References Insect growth rates Osbrink et al. (1987) Response to alarm pheromones by aphids Awmack et al. (1997) Effects of transgenic B.t Coviella et al. (2000) Nitrogen-based plant defenses Coviella and Trumble (1999) Cont….
- 18. Common name Host plant CO2 Conc. (ppm) Effect on Host plant Impact on Insect References Gypsy moth Sessile Oak 530 42% increase in Starch. Decrease N , increase in condensed tannins RGR reduced by 30% Schafeltner et al., 2004 Gypsy moth Red maple Amb.+300 Decreased N and Increased C:N ratio Reduced larval growth Williams et al., 2000 Gypsy moth White oak Amb.+300 Decreased N and higher TNC Growth reduction in early instar Williams et al., 1998 Gypsy moth Gray birch 700 Decrease N , increase in condensed tannins 38% decrease in pupal mass and decline in RGR Traw et al., 1996 Beet armyworm Upland cotton 900 Decreased N, Increased C:N 25% increased in consumption longer dev. time Coviella and Trumble,200 0 Elevated CO2 (eCO2) on insect-plant interaction
- 19. Tobacco Caterpiller Mung bean 600 Decreased N, increase in Starch and TSS Increased feeding and reduced growth rate Srivastava et al., 2002 Western flower thrips Common milk weed 700 Decreased N and C:N, higher above ground biomass Density decreased, and leaf area damaged increased by 33% Hughes and Bezzaz, 1997 Cotton Aphid Bt cotton 800 Increase C:N , plant height , Biomass and leaf area Increased fecundity Chen et al., 2005 Grain Aphid Spring wheat 750 Decreased N, Increased starch, sucrose, glucose, TNC , Free AA and soluble protein Population increased Chen et al., 2004 Cont……
- 20. Insects Take Bigger Bite - Plants grown in Elevated CO2 Under eCO2 soybean lose their ability to produce jasmonic acid, and that whole defence pathway is shut down. Attract many more adult Japanese beetles than plants grown under ambient level. The beetles lived longer, and produced more offspring, than those living outside Evan Delucia, 2008
- 21. ELEVATED CO2
- 22. 1.Chemical composition of maize grains grown under ambient (350ppm) and elevated CO2 (750 ppm) CO2 Level Measured indices Ambient CO2 Elevated CO2 Water (%) 68.9b 71.72a Nitrogen (mg g -1) 1.52a 1.31b TNC (mg g -1) 167.5b 174.8a Protein (g -1) 0.50a 0.41b Yin et al. (2010)
- 23. Life-history parameters of three successive generations (G1–3) of Helicoverpa armigera larvae fed on artificial diet and Maize grains Ambient CO2 Elevated CO2 Parameter G1 G2 G3 G1 G2 G3 Larval period(days) 10.7 aB 11.4 aB 15.5 aA 13.0 aB 14.6 aB 16.1 aA Pupal period (days) 9.50 aA 9.46 aA 10 aA 9.92 aA 9.80 aA 9.93 aA Adult period (days) 7.80 aB 7.33 aB 8.92 aA 7.85 aA 7.31 aA 8.23 aA Mortality 0.40 aA 0.34 bA 0.32 aA 0.44 aA 0.48 aA 0.41 aA Fecundity 661aA 586aA 565aA 702aA 386aA 589aA Fed on Artificial diet Yin et al. (2010)
- 24. Ambient CO2 Elevated CO2 Parameter G1 G2 G1 G2 Larval period(days) 14.0 aA 14.1 bA 13.3 aB 15.7 aA Pupal period (days) 9.44 aA 9.48 aA 9.29 aA 9.41 aA Adult period (days) 9.71 aA 9.31 aA 9.68 aA 9.03 aA Mortality 0.09 bB 0.32 0.37 bB 0.6 aA Fecundity 668aA 391ab 391bA 414aA Fed on Maize grains
- 25. Fed on Artificial Fed on Maize grains Result: Population consumption by cotton bollworm on maize will be significantly increased under elevated CO2 in the future Yin et al. (2010) 0 0.2 0.4 0.6 0.8 1 G1 G2 Individualconsumption onMaizegrains(g) Generation0 0.2 0.4 0.6 0.8 1 1.2 G1 G2 G3 Individualconsumption onartificialdiet(g) Generation Ambient CO2 Elevated CO2
- 26. TEMPERATURE
- 27. Global Top 10 Warmest years Years (Jan-Dec) °C °F 2010 0.62 1.12 2005 0.62 1.12 1998 0.60 1.08 2003 0.58 1.04 2002 0.58 1.04 2009 0.56 1.01 2006 0.56 1.01 2007 0.55 0.99 2004 0.54 0.97 2001 0.52 0.94 National Climatic Data Centre, NOAA, December 2010
- 28. Effect of Elevated temperature ---- Plants Parameter Effect Host plant Reference Decrease Qurcus robur Dury et al., 1998 Foliar Nitrogen Increased Cardamine hirsuta Poa annua Senecio vulgaris Spergula arvensis Benzemer et al., 1998 No effect Sugar maple- A. saccharum Williams et al., 2000 Leaf Water content Decrease Sugar maple Williams et al., 2000 Condensed tannin Increased Qurcus robur Dury et al., 1998
- 29. ….. Herbivorous insects 1. Extension of geographical range 2. Increased over wintering 3. Changes in population growth rate 4. Increased number of generations 5. Extension of development season 6. Changes in crop pest synchrony 7. Changes in inter specific interaction 8. Introduction of alternative hosts Bale et al. (2002)
- 30. Extension of geographical range and population dynamics of insect pests : • 10C rise would enable species to spread 200km Northwards or 140m upwards in altitude. (Parry et al.1989) • Earilar infestation by Helicoverpa zea in N. America (EPA,1989) and Helicoverpa armigera (Hub.) in North India and exploitation to new areas . (Sharma,2005;2010) • 20C temperature increase insects might experience one to five additional life cycles per season. (Yamamura & Kiritani,1998) • Population of rice stem borer & green leaf hopper increases with increasing winter temp. not by summer temp. . (Yamamura,et al .2006) • Mountain pine beetle, has extended its range northward by 300 km with temp. increase of 1.9oC (Logan and Powell, 2001).
- 31. Survival and reproduction : Of 46 species of butterflies that approached their northern climatic range in Britain three-quarters of them declined , dual factors of habitat modification and climate change are likely to cause specialists to decline, leaving biological communities with reduced number of species and dominated by mobile and widespread habitat generalists. Warren et al. (2001) Some species may be able to complete more generations in a year. This may be most noticeable in insects with short lifecycle such as aphids and diamond back moth. •In aphids a increase of 2oC temperature causes one to five additional life cycles per season. •Warm temperature have halved the time required to reproduce in Spruce beetle, Dentroctonus rufipennis.
- 32. Ostrinia nubilalis is predicted to become bivoltine due to increases in temperatures during the period 2025-50 Trnka et al. (2007) Larval development and adult fecundity of winter moth was adversely affected by increased temperature on Q. robur Dury et al. (1998) An increase in 1-30C in temp. will cause northwards shifts in potential distribution of Eoropean cornborer Ostrinia nubalis (Hub.) upto1,220 kms with an additional generation in all known areas currently occuring. Portal et al.1991.
- 33. Changes in crop pest synchrony : Associated advancement in the phenology of life history events for many plant and insect species . Climate change will disrupt or even eliminate mutualistic interactions among species, such as pollination and seed dispersion Of 1,419 species of pollinating insects on 429 plant species, between 17% and 50% of all pollinators analyzed suffered a reduction in food supply with a phenological advance of two weeks of their floral resources. (Memmott et al 2007) . Operophtera brumata (L.) winter moth eggs tend to hatch before the leaves of their host Quercus robur is available and in some years more than 90% of the eggs hatch before oak bud burst. (Visser & Holleman 2001)
- 34. At higher temperatures, aphids have been shown to be less responsive to alarm pheromone resulting in potential for greater predation. Changes in synchrony of prey –predator interaction : Awmack et al.2007 Temp. influcened the fecundity and sex ratio of Compoletis chloridae larval parasitoid of Helicoverpa armigera. (Dhillon and Sharma,2009) Oriental armyworm, Mythimna separata populations increases during extended period of drought ,which is detrimental to natural enemies. (Sharma et al.2002).
- 36. 1. Effect of increased temperature on oak procession caterpillar problem in Netherland OPC has increased steadily over the years, moving in north-eastern direction Observed 1°C increase in temperature and the corresponding increase in growing season length in the recent decades have stimulated the spreading Alexander et al.,2008 1991/1993 2006/2007 OPC distribution maps
- 37. 2.Interaction between Pentatomid bug, Oechalia schellenbergii and cotton bollworm, Helicoverpa armigera when feeding on peas Pea plants had reduced nitrogen content when grown under higher levels of CO2 and this in turn influenced the size of the cotton bollworm larvae Predatory bugs were more effective under higher CO2 levels because they appeared to be better at subduing the smaller bollworm larvae. Result indicating that elevated CO2 may benefit generalist predators through increased prey vulnerability. Within the parasititoids the specialists which are host specific are likely to be more adversely affected than generalist. Coll and Hughes,2008
- 38. Interactive Effects of eCO2 and eTemperature • Nitrogen concentration………Decreased. • C:N ratio……………Increased. • Carbon based secondary compounds……….No significant response. • Hervivors performance……………….No detectable Effect. Zvereva & Kozlov (2006)
- 39. Precipitation / Rainfall •Unpredictable rains might disrupt the parasitoids ability to track their caterpillar hosts. •Too much water will be devastating for some pests especially soil dwelling insects. •Rain drops can physically dislodge insects from their host plant and behavior patterns can be disrupted in small insects such as thrip. •Some pest species are suppressed by periods of rainfall , by outbreak of fungal diseases as observed among aphids on lettuce and Brassica crops. •It is anticipated that the cut worm outbreaks may become more frequent due to effect of summer rains . •Pesticide application and efficiency is also affected.
- 40. Impact of climate change on IPM •Many of the IPM programmes need to be modified greatly or to some extent to address several important effects of increasing temperatures. Each new technique recommended has to be evaluated whether and how it suits to changed pest dynamics due to climate change . Effects of climate change Revision in IPM recommended Insect development is more rapid at higher temperature and population develops faster and crop damage occurs more rapidly . Treatment thresholds based on insects per plant need to be reduced to prevent unacceptable loses. Even modest increase in temperature can reduce effectiveness of insect pathogens.(Sharce et al., 2007). Timing of use of biological control agents and their amount may need revision. Increased winter temperatures and elimination of frost may allow insect expansion into new areas. Such changes should be predicted earlier and suitable management practices be introduced.
- 41. •Responses of organisms to climate changes will be species-specific and might occur at different rates, potentially altering community structure and the ecological roles of several species in maintaining ecosystem processes and services. • Insects have great potential to develop physiological and behavioral adaptations, which may improve their fitness under new conditions. •This may ultimately lead to the formation of genetically differentiated population and possibly new species, especially when climatic change is associated with range expansion and host switch. •Biology and life cycles of several arthopods will keep altering under changes in climate that ultimately could affect many sucessful pest management practices . Conclusion
- 42. •Remote sensing , and GIS system can be helpful in developing forecasting systems of insect pest. To achieve these goals entomologist, agro-meteorologist, agronomist and statistician have to work as a team, only then some workable prediction models can be developed. • Best use of the basics of IPM such as field monitoring, pest forecasting, recordkeeping, and choosing economically and environmentally sound control measures will be most successful in dealing with the effects of climate change. • On the whole, there are still many unknowns in the climate change equation.
- 43. References: Awmack, C.S., C.M. Woodcock and R. Harrington. 1997. Climate change may increase vulnerability of aphids to natural enemies. Ecological Entomology. 22:366-368. Bale, J.S. G.J. Masters, I.D. Hodkinson, C. Awmack, T.M. Bezemer, V.K. Brown, J.Butterfield, A. Buse, J.C. Coulson, J. Farrar, J.E.G. Good, R. Harrington, S. Hartley, T.H. Jones. R.L. Lindroth, M.C. Press, I. Symrnioudis, A.D. Watt, and J.B. Whittaker. 2002.Herbivory in global climate change research: direct effects of rising temperatures on insect herbivores. Global Change Biology 8:1-16. Coviella, C. and J. Trumble. 1999. Effects of elevated atmospheric carbon dioxide on insect plant interactions. Conservation Biology 13:700-712. Hamilton, J.G., O. Dermody, M. Aldea, A.R. Zangerl, A. Rogers, M.R. Berenbaum, and E. Delucia. 2005. Anthropogenic Changes in Tropospheric Composition Increase Susceptibility of Soybean to Insect Herbivory. Envirn. Entomol. 34:2 479-485. Hunter, M.D. 2001. Effects of elevated atmospheric carbon dioxide on insect-plant interactions. Ag. Forest. Entomol. 3:153-159. Lewis, T. 1997. Thrips as crop pests. CAB International, Cambridge: University Press. 740 pp.
- 44. Petzoldt C and Seamann A. 2012.Climate Change Effects on Insects and Pathogens. Accessedonlineathttp://www.climateandfarming.org/pdfs/FactSheets/III.2Insects.Pathoge ns.Pdf Roth SK and Lindroth RL. 1995. Elevated atmospheric CO2: Effect on photochemistry, insect performance and insect parasitoid interactions. Global Change Biol. 1: 173-82. Osbrink WLA, Trumple JT and Wagner RE.1987. Host suitability of Phaseolulunata for Trichoplusiani (Lepidoptora: Noctuidae) in controlled carbon dioxide atmosphere. Envi. Entomol. 16: 639-44. Mostafa Haghani Æ Yaghoub Fathipour Æ Ali Asghar Talebi Æ Valiollah Baniameri 2007 Temperature-dependent development of Diglyphusisaea (Hymenoptera:Eulophidae) on Liriomyza sativae (Diptera: Agromyzidae) on cucumber. Journal of Pest Science (2007) 80:71–77 Intergovernmental Panel on Climate Change (2007) Fourth Assessment Report of the IntergovernmentalPanelon Climate Change. Available at www.ipcc.ch/ipccreports/assessments-reports.htm.4. Parmesan C (2006) Annu Rev Ecol Evol Syst
Editor's Notes
- Atmos. Co2 steadily rising fromm315 ppm in 1959to current 380ppm conc. To rise to as much as 500-1000 ppm by 2100.
- About 2/3rd of human induced emission over the last 2 century have come from fossil fuel burning and a third from land use change Deforastation and agriculture which contributes 14% of global GHG emission.(coservation tillage,residue mangementgreen manuring agro forestry system.) About 45% of these emission have remained in Atmos. The remaining absorved by ocean % forest which act as buffer.
- Relatively less ware temp .ming is expected in tropics as compared to temperate region s.by 2040 india is likely to experience an increase in annual mean surface air temp. of 1oC over land regions. Warming is going to be less prounced in khrif than rabi.rainfall erratic with less rainy days but of great intensity and uneven distribution.
- Temp. tolerant varieties,advancing date of sowing of rabi crops to counter terminal heat,frost management of hort.crops.water saving paddy.
- .more damage to heat sensitive crops like Maize n wheat ,have smaller impact on rice ,soybean .By 2030 most changes in crop yield negative.25% loss in second half of century with negative impact on yield of maize ,wheat &rice.
- Main effect of CC and pollution result in decreased abundance of decomposera & predators increased hervivory will have negative consequences for structure and services of entire ecosystem. Insects represent almost half of the biodiversity so far described (Speight et al 1999) and are central pieces on ecosystem structure and function (Crawley 1983). Because of their tight relationship with host plants, insect herbivores are expected to suffer direct and indirect effects of climate change through the changes experienced by their host plants. Crop plants are damaged by over 10,000 species of insects causing an estimated loss of 13.6% globally(Benedict,2003) and 23.3% in India(Dhaliwal et al.2004). Losses due to insect damage are likely to increase as a result of changes in crop diversity and increased incidence of insect pests due to global warming.
- Enriched atmospheric CO2 influences plant physiology, with direct consequences for plant productivity and biochemical composition. Plant chemical composition influences positive and negative trophic interactions, as well as decomposition, which will then feedback to atmospheric CO2 concentrations (Lindroth 2010).
- Increased CO2 = greater photosynthetic efficiency. Increases in photosynthetic rates by 20 to 60% (Cure, 1985). Laboratory experiments predict that 550 ppm will result in a 38% increase in rice crop productivity. further increases in CO2 concentrations may not have much impact on yields as rice apparently reaches a plateau in terms of photosynthetic acclimation (Baker et al. 1988). Decreases in stomatal conductance and transpiration rates of approximately 16 and 33%, respectively c3-rice wheat fruit lemon;c4-corn,sorghum,millet.
- Plants grown at elevated co2 of 475-500 ppm increase leaf photosynthesis by 40% and decreases whole plant water use by 5-20%,increased dry matte rby avg.17% aboveground and 30% below ground with yield increase12-24% in rice wheat soybean .Leaf carbohydrates starch &sugar/unit area increase by 30-40% nitrogen decrease by 13%due to dilution.protein conc. In wheat,rice,barley & potato tuber decreased by 5- 14%,as stomatal conductance decreases and plant take up less water &decrease in rate of assimilation of nitrate into organic compounds.
- In general the host plant quality declines with decreased leaf N & increase phenolics Changes in N is corelated to food consumption & phenolics to food digestability. herbivores would respond by increasing food consumption to compensate for the plant lowered nutritional quality reducing their growth rates and prolonging their development time, and by reducing food conversion efficiency Herbivores will respond toaltered status increased levels of CO2 by increasing their food consumption, prolonging development time, and reducing their growth rates and food conversion efficiency (Watt et al., 1995).
- This low nitrogen concentration, coupled with a high C/N ratio and its potential effects on plant secondary metabolism, means a lowered concentration of leaf protein and therefore reduced nutritive value to herbivores .Co2 will cause changes in plant secondary chemistry due to increased carbon supply & allocation to production of CBScompounds.Insec r going to respond by incresing consumption by 17%,rgr by 9%, and prolonging dev. Tm 4%.All these reduction would have potential to increase mortality by natural causes thereb uny reducing its abundance richness and diversity.
- Some species of aphid showed different response to diff .hp. There was increase in aphid pop. And consumption rate Of lady beetle increased when fed upon aphis gosphii by altering the prey structure thereby increasing BC.
- Reduction of IGR of cabbage semilooper was observed on lima bean and increased feeding. At higher co2 aphids become less responsive to aphid alarm pheromone for several generations when uder attack resulting in the potential for greator predation. reduction in Bt toxin in transenic cotton ck-12 under increase co2 atmos.
- The response of insects varied differently and was not consistant across host plants. leaf chewing insects generally increased their consumption of foliage under elevated co2 to compensate reduced nutritional quality.
- The phloem feeding and whole cell feeding insects responded positively to eco2 with increase in pop size and decrease in dev time.sap suckers r only functional group to show positive response to eco2.
- how elevated CO2 and temperature affect plant defensive compounds (allelochemicals) is considerably less predictable. Recent studies indicate that exposure to elevated CO2 suppresses the plant defense hormone jasmonic acid (JA) while stimulating production of salicylic acid (SA).
- To test the effect of elevated CO2 on multiple successive generations of h a on maize and about the direct effects of increased environmental CO2 on developmental time and consumption .N and protein content decresed by 13.8% &18% but water content &TNC:protein ratio increased by 41&33.9%.
- In the first series of experiments, regardless of co2 steady pop. abundance & unchanged individual consumption resulted in stable pop dynamic across 3 sucessive generation.
- Significant increase consumption was noticed in 2 sucessive generations hiher mortality & lower fecundity resuled in lower pop.in 1st generation in 2ndmortility appeared to increase with no significant difference in fecundity.
- The effects of elevated CO2 on three successive generations of cotton bollworm fed on artificial diet were weak, or even non-existent, (2) elevated CO2 increased the consumption when cotton bollworm were fed maize. Our study also suggests that the damage inflicted by cotton bollworm on maize (a C4 plant) will be seriously affected by the increases in atmospheric CO2, which is unlike our previous results for spring wheat (a C3 plant).
- Global average temperatures already have increased by 0.8°C, and the last two decades of the 20th century were the warmest in at least four centuries, and possibly in several millennia. At current rates of fossil fuel use, global mean temperatures will rise by 4°C by the end of the 21st century. as exotherms they can be very sensitive to temperature, which affects their life cycle, population size, and geographic distribution
- Global temperature is expected to ride by approximately 0.2% per decade or between 1.4 and 6.4 by 2100 which has increased by 0.740C in 20th century. Sea level has raised by 17 cm. Losses due to insect damage are likely to increase as a result of crop diversity and increased incidence of insect pest.
- Differential response was noticed due to elavation of temp. in different species .In Quercus robur(english oak) etemp.resulted in decreased leaf nitrogen and increased condensed tannin concentration. while eco2 increased total carbon based phenolics. Increased temperature have drastically affected rice production in Philippines 10% reduction in yield per 10C rise in temperature (Peng et al..2004).An increase in 60C in temperature and precipitation defecit of 300 mm reduced the maize yield by 36% in European Union (Clais et al.2005). Different spp possess the different effect- spp specific Pedunculate Oak or English oak(Qurcus robur) , Hairy Bitter cress(Cardamine hirsuta), annual bluegrass(Poa annua)
- High mobility and rapid pop. growth will increase the extent of losses due to insect. Whereas geographical distribution of insect contained in tropical and sub tropical region will extend to temperate regions along with a shift in areas of production of host plants. while distribution and relative abundance of insects vulnerable to high temp .in the temperate regions may decrease or find suitable alternative habitat at greater latitude.
- As the climate warms up those species that r not limited by vegetation but restricted by temp. will be able to move northwards in N.hemi .and southwards in S hemi .as rapidly as their dispersal mechanism will allow .In addition those areas that are not favourable at present may become suitable as rise in temp .will result in greater ability to overwinter at higher temp. Increased temp. will accelerate dev. resulting in more cycles of generations& crop damage/yr. with less time between generations.
- For all insect species ,higher temp. below the species upper threshold limit will result in faster dev. & rapid increase increase in pest pop. As the time to reproductive maturity will be reduced considerably in addition to change in development tm .Insects may also evade CC stress through changes in life cycle. Insect pop. From higher temp .may have higher fecundity and shorter growth stage durations to increase fitness.
- . Polyvoltine species will profit with accelerated development rate allowing for earlier compilation of life cycle and establishment of additional generations within a season.
- For many insect herbivores, synchronization to plant phenology is crucial, as development outside the period of optimal conditions often has severe fitness consequences (VanAsch & Visser 2007). Global warming has advanced, for example, bud burst and the first flowering date of plants, disrupting interactions with herbivores and flower visitors. But, an important point in the understanding of the immediate impacts of climate change is the extent to which species will alter their phenologies, in response to altered temperatures, leading to both temporal and spatial mismatches between, for example, plants and herbivores, plants and pollinators, and hosts and parasitoids. Successful life-cycle completion in many specialist insects requires a very tight synchrony with host plant phenology.
- CC may cause temporal asynchrony between interacting po.if host and parasitoid respond differentially to changes in climate, it may introduce partial refuge effect that can reduce parasitism .The lack of temporal coincidence between searching parasitoids and hosts can evade climte change stress through changes in life cycle. Hosts may pass though vulnerable life stages more quickly at higher temperatures, reducing the window of opportunity for parasitism thereby reducing it. Temp. not only affects rate of dev. of insect pests but also have profound effect on fecundity and sex ratio of parasitoids.
- The OPC is an egg-overwintering insect and mainly found on solitary oaks Due to increase in summer temperature in north of Netherlands the OPC distribution area is likely to expand further; in 2020 the entire country could become an “OPC region”
- Oechalia schellenbergii, an omnivorous bug feeds on both plants and preys on bollworm, it requires prey to complete its dev. it performed best when fed with mixed plant-prey diet regardless of co2 level. Best performance when fed with elavated co2 treament as prey were smaller and easier to overcome.
- The nitrogen conc .reduced and this reduction was stronger for woody compared to herbaceous plants.Ratio o C:N exhibited opposite trend by increasing .Carbon based secondary compounds did not show a significant response. The hervivors performance had no detectable effect.
- Precipitation & extreme events such as flooding & hurricane are also predicted to increase with less certainity about magnitide of these changes and how it will effect ecosystem functioning and ecological role of insect.