Climate Change and Crops | Term Paper | Geography

Here is a term paper on the ‘Impacts of Climate Change on Crops’ especially written for school and college students.

Term Paper Contents:

1. Term Paper on the Introduction to Climate Change
2. Term Paper on the Impact of Climate Change on Diseases
3. Term Paper on the Geographical Distribution of Host and Pathogen in Crops
4. Term Paper on the Physiology of Host-Pathogen Interaction in Crops
5. Term Paper on Disease Management in Crops
6. Term Paper on the Impact on Weeds on Crops
7. Term Paper on the Effect of Increased Temperature on Crops
8. Term Paper on the Effect of Changing Precipitation
9. Term Paper on Controlling of CO2, Climate and Weeds
10. Term Paper on Weed Biology and Its Impact on Human Health
11. Term Paper on the Impact of Climate Change on Insects
12. Term Paper on Elevated Temperature could Increase Pest Population
13. Term Paper on Elevated Temperature could Decrease Pest Population
14. Term Paper on the Effect of Rising CO₂ Levels on Crops
15. Remarks on the Impact of Climate Change on Crops

Term Paper # 1. Introduction to Climate Change:

With the onward march of the dial hour, as human civilization makes its existence felt in the twenty first century, there has been a paradigm shift in the arena of population, demand for food and food production technologies. Human activities, driven by demographic, economic, technological and social changes do have a major effect on the interactive global systems constituting of land, water, vegetation and climate.

Global population on the rise can be visualized by the changes in the land use pattern and rapid urbanization. Shrinkage in the land resources meant for agriculture is of a major concern. Globally, some 25 crops stand between the rapidly expanding world population and starvation. As it is evident that atmospheric concentration of greenhouse gases is on the rise due to anthropogenic intervention, they will have a profound effect on climate change.

Uncertainly of climatological factors will further accentuate the challenges of increasing sustainable agricultural production. Climate changes will have many facets – except accumulation of greenhouse gases, changes in other radioactively active substances and increased cloudiness caused by greater evaporation in a warmer climate may offset some of the greenhouse effect.

The expected rate of increase of the temperature of the earth’s surface is 0°C per decade while the global mean concentration of water vapour in the lower troposphere would increase at the rate of 6 per cent per 1°C warming, which in turn would lead to an increase in global precipitation of 0.5 per cent/°C warming.

Farmers differ in their opinion regarding climate changes, pest and crop protection, but they unanimously agree to the fact that there will be an increase in insect population, fungal disease and weeds. Hence the risk of loss due to these biotic factors is likely to increase. The range of many insects will change or expand and new combination of disease and pests may emerge as natural ecosystems respond to shift in temperature and precipitation profiles.

The effect of climate on pest may add to the effect of other factors such as the over use of pesticides and the loss of biodiversity, which contribute to plant pest and disease outbreak. Constraints from diseases, insects or weeds have not been considered to any significant extent in any impact assessment of natural or managed ecosystems despite recognition of their significance.

For instance, a doubling of CO₂ has been conclusively shown to increase C3 and C4 crop yield by about 33 per cent and 10 per cent respectively in over 1000 studies, but whether these benefits will be realized in the presence of pest, disease and weeds is yet to be inferred.

Term Paper # 2. Impact of Climate Change on Diseases:

Plant diseases are significant constraint to global productivity of crops and worldwide losses from diseases range from 9 to 16 per cent in wheat, rice, barley, maize, potato, soybean and coffee. Only in USA alone, fungicides worth over 5 billion US $ are used to control disease. The economic impact of disease stems from losses in productivity, the cost of disease management and the economic penalty paid for having to grow less profitable alternative crops.

The Irish potato late blight (1845-46) and the great Bengal famine (1943) are grim reminders of the fact that the socio political repercussions of major epidemics go far beyond simple economic impact. In the recent times, diseases such as Panama wilt have resulted in the abandonment of entire banana plantation in Central America.

The classic disease triangle emphasize the role of physical environment in the plant diseases as no virulent pathogen can induce disease on a highly susceptible host if weather conditions are not favourable. Weather influences all stages of host and pathogen life cycles as well as the development of disease. Correlation between weather and disease are routinely used for forecasting and managing epidemics and disease severity over a number of years and can fluctuate according to variations in climate.

Most research on how climate change influence plant diseases has concentrated on the effects of a single atmospheric constituent or meteorological variable on the host, pathogen or the interaction of two under controlled conditions. In a dynamic environment, interactions are more complex as multiple biological and climatological factors are involved.

Climate change has potential to modify host physiology and resistance, alter stages and rates of development of the pathogen, shift in the geographical distribution of host and pathogen, change the physiology of host-pathogen interaction and changes in the management strategies.

Term Paper # 3. Geographical Distribution of Host and Pathogen in Crops:

New disease complexes may arise and some disease will lose their economic importance if warming causes a pole ward shift in agro-climatic zone and host plants migrate into new regions. Carter et al (1996) predicted that maize could be cultivated in southern Finland by 2050 and warming will extend the northern limit for cereal cultivation. At the same time risk of damage from late blight of potato would increase in all regions.

Pathogens would follow the migrating hosts and their dispersal and survival between seasons and changes in the host physiology and ecology in the new environment would largely determine how rapidly the pathogens establish in the new environment. Facultative parasites with broad host range would mostly fall in this category, although obligate parasites may also expand their host range to infect plant in their proximity.

If only climatic effects are considered, changes in geographical distribution itself may not have a major economic impact on crop production. Impacts only become obvious when associated changes such as terrain, remnant, vegetation, soil characteristics etc. are considered.

Using three temperature change scenarios and a 20 per cent increase in rainfall, Brasier and Scott (1994) predicted that global warming will make the pathogen, Phytopthora cinnamomi more severe in regions of Europe where it is currently present and spread it in northward and eastward direction. Temperature and rainfall were considered in simulation studies to predict the impact of climate change on rice blast caused by Pyricularia oryzae.

It was found that rainfall had no significant effect on blast epidemics but changes in temperature had significant effect on five Asian rice-growing countries, included in the simulations. However, there was variation of impact with the agro-ecological zone. In cool subtropical rice growing zones, such as Japan there was higher risk of rice blast disease where as in the humid tropics and sub tropics such as Philippines there was lower risk of disease with increased temperature.

Pathogenic genera with broad host range such as Rhizoctonia, Sclerotium, Sclerotinia etc. will have a tendency to migrate from agricultural crops to natural plant communities. Similarly, pathogens, which are normally less aggressive in natural plant community, could devastate crop monocultures growing in close proximity.

Pathogens may extend their host range to cause new disease problems in migrating crops. For example, Erwinia amylovora, the fire blight bacterium was pathogenic to some indigenous plant of the family Rosaceae without causing much loss but when European settlers grew apples and pears in some region, the bacterium caused severe losses.

Similarly, the coffee rust disease was facilitated by growing an introduced susceptible host Coffea arabica in a region where the native pathogen, Hemileia vastatrix was already present on alternative hosts in the forests outlining the coffee plantation.

If the frost line moves north in the northern hemisphere, higher winter temperatures could be accompanied by increased survival of insects. For virus-vector aphids, this could lead to higher incidence of virus disease, especially in that region where the timing of virus arrival is linked to winter survival and spring flight of aphids. Barley yellow dwarf polyvirus (BYDV) and several viruses of potato and sugar beet show significant increase with warmer winters.

Term Paper # 4. Physiology of Host-Pathogen Interaction in Crops:

i. Increased CO₂:

Recent findings on the physiological, biochemical and molecular mechanisms of host-pathogen interaction under high CO₂ and/or other elements of global change are very encouraging, although reduced stomatal opening, increases in leaf area and duration, leaf thickness, branching, tillering, stem and root length and dry weight are well known effects of increased CO₂ on many plants. Faster development of certain diseases under elevated CO₂ was reported in the early 1930.

In a comprehensive review of literature covering the period 1970 to 1993, Manning and Tiedemann (1995) concluded that while not much is known about the influence of elevated CO₂ on plant diseases, potential impact on disease could be predicted from known effects of CO₂ on host plants and their pathogens.

They suggested that elevated CO₂ would produce increased plant size and canopy density with high nutritional quantity foliage and microclimates more conducive to development of rust, mildews, leaf spots and blights. Necrotrophic pathogens, which will overwinter under warmer conditions, may increase in their severity as a result of enhanced inoculums survival on the greater amount of crop residues.

More recently a mixed report of enhancement and reduction of plant disease severity under elevated CO₂ have brought to the fore two important facts. Firstly, the initial establishment of the pathogen may be delayed because of modification in pathogen aggressiveness and/or host susceptibility. Colletotrichum gloeosporioides showed delayed or reduced conidial germination, germ tube growth and appressorium production when inoculated onto susceptible Stylosanthes scabra plant under increased CO₂.

In barley, infection of Erysiphe graminis hordei caused larger but delayed reduction in host growth at elevated CO₂. In these examples, host resistance may have increased because of changes in host morphology, physiology, nutrient and water balance. A decrease in stomatal density increases resistance to pathogen that penetrates through stomata. In barley, although the thickness of epicuticular wax did not play a role in resistance to E. graminis hordei, plants in elevated CO₂ were able to mobilize assimilates into defense structures including the formation of papillae and accumulation of silicon at sites of appressorial penetration.

Secondly, an increase in the fecundity of the pathogen under elevated CO₂ occurs. Established colonies of E. graminis hordei and C. gloesporioides grew faster when the CO₂ concentration is doubled. However, the latent period was extended under high CO₂ conditions, in all pathogen studies so far, because of delay and/or reduction in spore germination and initial establishment of the pathogen.

For pathogens with broad genetic diversity, increased population size and the number of generation in conducive microclimate may lead to the development and proliferation of well adopted and possibly more destructive sub population.

ii. Increased Temperature:

Elevation in temperature and duration of exposure can modify host physiology and resistance. An increase of yield by 10 -15 per cent in wheat and soyabean and 8 per cent in rice and maize have been reported by an increase of 2°C temperature coupled with ± 20 per cent precipitation and doubling of CO₂. However, global yields of all four crops were reduced with 4°C increase indicating a threshold of compensation for the direct effect of CO₂.

Information regarding heat induced susceptibility and temperature sensitive genes are available. In some forage species, at higher temperature lignification of cell walls increases and this can enhance the level of resistance to pathogen. On the contrary, an increase in temperature above 20°C can inactive pg3 and pg4 genes conferring resistance to oats against stem rust caused by Puccinia graminis avenae. Severe drought condition might cause severe diseases by Armillaria spp. that are normally not very pathogenic.

iii. Increased Ozone and Ultraviolet B:

The effect of elevated ozone on plant metabolism, crop yield and productivity plant health, host-pathogen interaction and host defence mechanism have been extensively studied. Of the 49 bacterial and fungal pathogens examined, exposure to elevated ozone concentration enhanced disease in 25, reduced 14 and did not affect ten.

Ultraviolet B (UV-B) also cast a major effect on crop and growth and life cycle of pathogens. The effect of UV-B radiation on diseases is mainly through altered host physiology and morphology. Continued exposure to enhanced UV-B radiation lowers the level of antifungal compound in foliar plant parts.

UV-B has been reported to reduce tolerance of rice to blast caused by Pyricularia grisea and although higher UV-B reduced plant biomass and leaf area, there was no increase in blast severity. Again, out of seventeen reported instances between 1970 and 1993, enhanced UV-B increased diseases in ten, reduced five and had no effect in two.

Term Paper # 5. Disease Management in Crops:

As the information level regarding the impact of climate change on plant patho-system in scanty, it is difficult to assess implication for disease management. The management strategies may require restructuring under the changed context. It may be assumed that the effect would occur chiefly through influence on host resistance or chemical and biological control agent.

i. Host Resistance:

Cultivar resistance to pathogen may become more effective because of increased static and dynamic defenses from changes in physiology, nutritional status and water availability. Durability of resistance may be jeopardized, if the number of infection cycle escalate within a growing season, due to either increased fecundity, more pathogen generation per season or more suitable microclimate for disease development. This may lead to more rapid evolution of aggressive pathogen races. Colletotricum gloeosporioides exhibited a gradual increase in fecundity under elevated CO₂ conditions.

ii. Chemical Control:

Fungicides will be affected by the climate change in either of the two ways. Firstly, changes in crop plants, morphologically or physiologically due to increased CO₂ could affect uptake, translocation and metabolism of fungicides. Due to increased thickness of the epicutiular wax layer on leaves, caused by increased CO₂, uptake of fungicides will be slow and/or reduced by the plants.

Increased canopy size will reduce spray coverage, and dilute the active ingredient in the host tissues. On the contrary, increased metabolic rates due to higher temperatures would result in faster uptake by and greater toxicity to the target organism. Similar observation were reported in herbicides, chlorotoluron.

Secondly, the dynamics of fungicides residues maybe changed due to changes in temperature and precipitation. Increase in the frequency of intense rainfall will lead to increased wash off of fungicides, and hence reduced control. Again for certain fungicides, precipitation following application may result in enhanced disease control because of a redistribution of the active ingredient on the foliage.

iii. Biological Control:

One of the major problems with application of biological control for plant disease management in the field has been the vulnerability of bio-control agent population to environmental variations and extremes. If appropriate temperature and moisture are not consistently available, bio-control agent population may not recover as rapidly as pathogen population when conducive conditions recur. Changes in temperature may have highly non-linear effect on tri-trophic interaction of host, pathogen and bio-control agent as observed in wheat.

iv. Quarantine and Exclusion:

Climate change will put extra pressure on agencies responsible for exclusion as a plant disease control strategy. In some regions, certain diseases of economic importance do not occur because the climatic conditions are not congenial for the pathogen. Use of Geographical Information System (GIS) and climate matching tools may assist quarantine agencies in determining the threat posed by a given pathogen under current and future climates.

v. Impact Models:

In order to understand the complex interaction of atmospheric, climatic and biological factors with technological and socioeconomic changes, quantitative or modeling approaches are more pertinent for impact assessment. Guidelines for such model based assessments are the need of the day and the preliminary frame work of the same has been reported. Modelling approaches are based on climate matching which involves the calculation of a “match index” to quantify the similarity in climate between two locations.

The match index is based on the two variables such as monthly minimum and maximum temperatures, precipitation and evaporation. Several software packages namely BIOCLIM, CLIMEX, HABITAT, WORLD etc. often come with additional useful features such as internal algorithms for generating “climatic surfaces” through interpolation between locations. Brasier and Scott (1994) used CLIMEX program to map region in Europe favourable or unfavourable for Phytophthora cinnamomi, a soil born oomycete, responsible for oak decline disease.

Empirical models have been used to study the effect of climate change on diseases of rice and wheat whereas population models have divulged considerable information on late blight of potato. Simulation models have been used extensively to predict yield of various crops in different agro ecological zones under climate change. Luo et al. (1995; 1998a; 1998b) have used simulation models to study the combined effects on yield of increased temperature, elevated UV-B radiation and rice blast disease.

Term Paper # 6. Impact on Weeds on Crops:

Effect of Increased CO₂:

Weed flora has a genetic diversity, which exceeds that of the cultivated crops. If a resource component (light, water, nutrients or carbon dioxide) is altered within the environment, it is more likely that weeds will show a greater growth and reproductive response. Weed species have C3 and C4 photosynthetic pathways, the later being more than the former.

So, weed species having the C4 photosynthetic pathway will show a smaller response to atmospheric CO₂ relative to C3 crops. On the contrary, it can be opined that the range of available C3 and C4 weeds present in any agronomic environment is usually not taken into consideration in assessing these changes. It has been reported that the number of obnoxious weed species associated is almost ten times than that of cultivated crops.

Hence, if a C4 weed species does not respond, it is likely that a C3 weed species will. In addition, many growers experienced that the worst weeds for a given crop are almost homologous in growth habit or photosynthetic pathway to the main crop. They are often the same uncultivated or “wild” species of the crop, e.g. oat and wild oat, sorghum and shatter cane, rice and red rice etc.

In a weed-crop competition study, where the photosynthetic pathway is the same, with the increase in CO₂ concentration in the environment, usually weed growth is favoured. In addition to agronomic weeds, there is an additional category of plants that are considered “noxious” or “invasive” weeds. These are usually non-native plants, whose introduction results in widespread economic or environmental consequences (e.g. water hyacinth).

Most of these weeds reproduce by vegetatively i.e. by roots, stolon’s, etc. and recent studies reveal that as a group, these weeds may show a strong response to increases in atmospheric CO₂. The mechanism is however, yet to be clearly understood about the role played by the escalating concentration of CO₂ in the in situ proliferation of these weeds.

The data that are available on the response of weeds and alterations in weed ecology due to the changing climate are limited. Information regarding the weed interaction with other abiotic factors like temperature, nutrient availability and precipitation is wanting and needs to be generated. Effect of other biotic factors like fungi, nematodes and bacteria on the weed flora in the changing environment needs to be assessed.

Term Paper # 7. Effect of Increased Temperature on Crops:

Escalation in temperature implies an expansion or bio-invasion of weeds into higher latitudes or higher altitudes. Very aggressive weeds that are currently found in the warm equatorial regions are limited in the temperate regions by virtue of low temperature. In other words, temperature forms an ecological barrier in the spread of the weed species.

For example, many C4 grass weeds are serious problems in the southern U.S. but their incidence is not reported at problem levels in the U.S. Corn Belt. Studies have shown that itch grass, a profusely tillering, robust grass weed could invade the central Midwest and California with only a slight warming trend.

A root parasite of corn, witch weed, which is limited to the coastal plain of north and South Carolina is speculated to be established in the Corn Belt with disastrous consequences with an increase of temperature. The current distribution of both Japanese honeysuckle and kudzu is limited by low winter temperatures but increase in temperature could extend their northern limits by several hundred miles.

Term Paper # 8. Effect of Changing Precipitation:

On Crops:

Both excess and scanty rainfall can predispose the plants to diseases and pest attack. Response to drought in agronomic conditions is dependent on species and cultural conditions. Any factor which increases environmental stress on crops may make them more vulnerable to attack by insects and plant pathogens and less competitive with weeds.

On Insects:

Just like temperature, alteration in precipitation can have an impact on insect pests, predators and parasites resulting in a complex dynamics. Some insects are sensitive to precipitation and are killed by heavy rains e.g. onion thrips. Hooding the soil has been used as a control measure for those insects that over winter in soil. Fungal hyper parasites of insects are favoured by high humidity and their incidence will be increased with the lengthening period of high humidity and vice versa.

Term Paper # 9. Controlling of CO₂, Climate and Weeds:

Chemical management of weeds i.e. herbicide intervention will have a direct effect if there is any alteration in the environmental factors. Changes in temperature, wind speed, soil moisture and atmospheric humidity can influence the effectiveness of herbicide applications. Thicker cuticle development or increased leaf pubescence due to drought conditions can result in reduced herbicide entry into the leaf.

These same variables can also interfere with crop growth and recovery following herbicide application. Herbicides will be most effective when they are applied to plants at an active growth stage i.e. their metabolic activity is very high. This is only possible when the plants are free from environmental stress.

There are several reports that highlight that the efficacy of herbicides is greatly reduced with the rising CO₂. The mechanism for this reduction is yet to be deciphered. A greater root to shoot ratio and subsequent dilution effect of glyphosate was observed in case of Canada thistle when grown in field at elevated CO₂ conditions.

However, ubiquitousness of the response is yet to be defined. The observed phenomenon that CO₂ does reduce herbicide efficacy tantamount to additional work that is to be done to revise herbicide specificity, concentration and application rates as possible means of adaptation.

Biological control of weeds by natural or manipulated means is likely to be affected by increasing atmospheric CO₂ and climatic change. Climate, as well as CO₂ could alter the efficacy of weed bio-control agents by potentially altering the development, morphology and reproduction of the target weed. Changes in the C: N ratio and modified feeding habit and growth rate of herbivores are directly affected by CO₂.

As per the reports of Patterson (1995), warming could also result in increased overwintering of insect populations and changes in their potential range. Although this could increase both the biological control of some weeds, it could also increase the incidence of specific crop pests, with subsequent indirect effects on crop-weed competition.

Synchronization between development and reproduction of bio-control agents and their selected targets is a mandate for successful bio-control. In a changed environmental condition of climatic change and climatic extremes, this synchrony is difficult to maintain. Whether it will be a boon or a bane needs to be seen.

The most popular and accepted means of controlling weeds in developing countries is mechanical removal. Tillage either by animals or mechanical means is regarded as a global method of weed control in agronomic systems. Below ground carbon storage with subsequent increases in the growth of roots or rhizomes, particularly in perennial weeds is an evident expression of elevated CO₂ in the environment.

Thus, mechanical tillage may lead to additional plant propagation in a higher CO₂ environment, with increased asexual reproduction from below ground structures and negative effects on weed control e.g. Canada thistle. New strategies are available to combat the weed menace in the changing climatic conditions, but the cost of implementing such strategies (e.g. new herbicides, higher chemical concentrations, new bio-control agents) is high and require considerable amount of time.

Term Paper # 10. Weed Biology and Its Impact on Human Health:

Weeds affect human health through allergenic reactions, skin irritations, mechanical injury or internal poisoning is a reported fact. As on date science is at a nascent stage to quantify how climate changes, especially changes in CO₂, may affect specific weed population associated with human health.

Changes in pollen production and allergen city in common ragweed (a recognized cause of allergic rhinitis) with changing CO₂ and temperature in both indoor and in situ experiments have been reported and further research on how escalating CO₂ concentration can affect both the growth and toxicity of poison ivy is ongoing.

Term Paper # 11. Impact of Climate Change on Insects:

Temperature is presumably the environmental criterion, which has a profound influence on insect behavior, distribution, development, survival and reproduction. The main reason being, the insect are poikilothermal i.e. their body temperature is approximately the same as that of the environment. Insect life stage predictions are most often calculated using accumulated degree-days from a base temperature and bio-fix point.

It has been reported that the effect of temperature on insects largely masks the effects of other environmental factors. It has been estimated that with a 2°C increase in temperature, insects might experience one to five additional life cycle per seasons. Hamilton (2005) and Hunter (2001) found that moisture and CO₂ effects on insects are also of importance in a global climate change setting.

Term Paper # 12. Elevated Temperature could Increase Insect Pest Populations:

Increased temperature can potentially affect insect survival, development, geographical range and population size. Depending on the development strategy of an insect species, temperature can exert different effects. Cicadas and arctic moths, which take several years to complete one life cycle, will tend to moderate temperature variability over the course of their life history. Some insect like cabbage head borer, onion borers develop more rapidly during periods of time with suitable temperatures.

As scientists use degree-day or pathology based models to predict the emergence and the potential to damage of these insects increased temperature will accelerate development of these types of insects resulting in more generation and subsequently more crop damage in a year.

Temperature may change gender ratios of thrips potentially affecting reproduction rates. Insect that spend major parts of their life history in the soil is slowly affected by temperature fluctuation than the ones that are above the ground because soil provides an insulating medium that will tend to buffer temperature changes more than the air.

Insect species diversity per area tends to decrease with higher latitude and altitude, which means that rising temperature could result in more insect’s species attacking more host in temperate climate. Based on evidence developed by studying the fossil record, it has been conducted that the diversity of insect species and the intensity of their feeding have increased manifold with increasing temperature.

Natural enemies and host insect population may respond differently to changes in temperature. Parasitism could be reduced if host populations emerge and pass through vulnerable life stages before parasitoids emerge. Host may pass through vulnerable life stages more quickly at higher temperature, narrowing the opportunity for parasitism.

Term Paper # 13. Elevated Temperature could Decrease Pest Population:

Monophagous or oligophagous insects are confined to a specific single or few set of host crops. Due to rise in temperature, farmers may be discouraged to grow these specific crops resulting in the dwindling population of pest due to starvation and dearth of food.

The same environmental factors that affect the insect pests can affect their predators and parasites resulting in an escalated, aggressive mode of hyper parasitism. At higher temperature, aphids have been shown to be less responsive to the aphid alarm pheromone, they release when attacked by predators and parasitoids resulting in potential increase of pest control.

Term Paper # 14. Effect of Rising CO₂ Levels on Crops:

Usually CO₂ impacts on insects are thought to be indirect as impact on insect damage result from changes in the host crop. It has been observed that the soyabean grown in elevated CO₂ atmosphere had 57 per cent more damage from insects than those grown in present day atmosphere. It is assumed that measured increases in the level of simple sugars in the soyabean level may have stimulated the additional insects feeding.

Recently, free air gas concentration enrichment (FACE) technology was used to create an atmosphere with CO₂ and O₂ concentration similar to what climate change models predict for the middle of the 21^st century. Researchers have observed that insects sometimes feed more in leaves that have a lowered nitrogen content in order to obtain sufficient nitrogen for their metabolism. Increased carbon to nitrogen ratios in plant tissue resulting from increased CO₂ levels may slow insect development and increase the length of life stages vulnerable to attack by parasitoids.

Effect on Farmers:

As entomologists expect that insects will expand their geographic range and increase reproduction rates along with over wintering success, farmers will confront more types and higher number of insects to manage. This in turn means more round of insecticide spray as compared to the present time. Moreover, some classes of pesticide e.g. pyrethroids and spinosad have been shown to be less effective in controlling insects at higher temperatures.

With more insecticide applications being predicted, the probability of applying a given insecticide in a season will increase and hence the risk of developing insecticide resistance is catapulted. Cultural practices adopted by the farmers will also undergo certain changes.

For example, using crop rotation as an insect management strategy could be less effective with earlier insect arrival or increased over wintering of insects. Row covers used for insect exclusion might have to be removed earlier to prevent crop damage by excessive temperature under the covers.

Term Paper # 15. Remarks on the Impact of Climate Change on Crops:

Climate change effects are challenging to investigate but are potentially of great importance. Hence, the topic has been reviewed and researched upon, continuously. Increased focus has been diverted towards how a changing environment affects evolution of pest and several question have cropped up – which pest characteristics (such as, frequency of generation and proportion of sexual reproduction) affect the rate of adaptation in both host and pest population?

Are invasive plant species better able to adapt to climate change and move to new areas rapidly, leaving the pest behind? Keeping these questions at the back drop, it is known that climate change will alter the suitability of crops and other plants for certain locations.

However, information gathered so far has been fragmented and a comprehensive analysis of climate change impact on biotic stress is limiting with the present knowledge base. Apart from the technical constraints, the most significant bottleneck to climate change impact assessment is the inability to predict how technological and socioeconomic forces will interact with atmospheric, climate and biological factors to shape the future agriculture.

The land use pattern change in response to market demands, transgenic technology and new chemicals for pest management are perhaps more priority area in agricultural research, but climate change and climate variability add another layer of complexity and uncertainty onto a system that is already exceedingly difficult to manage.