Plant Disease Management Strategies Under Climatic and Atmospheric Change

Research shows that increasing population growth will cause an intensification of food scarcity. Therefore, plant disease management practices must be improved to mitigate the damaging effects of already induced yield loss. Because pests and diseases have varying effects on plants, however, control practices must be catered to the specific location, crop, and type of pest. With climatic and atmospheric changes, plant disease management strategies have to adjust in accordance with these new conditions. Some ways in which temperature change and atmospheric change may affect the relationship between plants and pathogens are by altering the host plant’s susceptibility and by reducing the pathogenic resistance, as well as other changes. Juroszek et al. (2011) conducted a review on disease management practices and researched the ways in which these tactics will have to be altered in accordance with climate change. The authors specifically looked at fungal plant pathogens in agriculture<!–[if supportFields]> XE “agriculture” <![endif]–><!–[if supportFields]><![endif]–> and horticulture. —Daniela Hernandez
Juroszek, P., von Tiedemann, A., 2011. Potential Strategies and future requirements for plant disease management under a changing climate. Plant Pathology 60, 100–112.

The authors researched some possible agronomic practices that can mitigate the impact of plant diseases. Generally speaking, planting a diverse set of crops may significantly decrease the threat of plant disease associated with monocultures. The authors additionally point at the importance of crop rotation as a disease management strategy, especially under climate change. Other strategies include changing the harvest date, to avoid pathogen infection, as well as planting cultivar mixtures and intercropping. The benefit of the latter two strategies is that they have the potential of slowing down the rate of epidemics. At the same time, however, the intercrop implemented can outcompete the crop being managed, thus reducing yield. The authors suggest more research be conducted to investigate the extent of these effects.
Juroszek et al. also researched the implementation of resistant crops as a disease management strategy under the climate change criteria. According to the authors, some of the factors that need to be taken into consideration when looking at disease resistance and the implementation of possible resistant crops are temperature, “…leaf wetness, nutrient status (e.g. nitrogen<!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> fixation<!–[if supportFields]> XE “nitrogen fixation” <![endif]–><!–[if supportFields]><![endif]–>), soil type and availability of water (105).” Research suggests that increased CO2 levels can lead to acceleration in the pathogen evolution for increased aggressiveness. Juroszek et al., however, resist making any ultimate correlation, as much more research is needed.
The researchers additionally looked at fungicides as possible disease management strategies under climate change. Studies show that increasing CO2 will require an additional amount of fungicides to those plants negatively affected by this change in atmospheric condition. Other studies, however, show how increasing temperatures reduce the efficiency of certain fungicides against pathogens. An increase in CO2and temperature can also lead to morphological changes to the plant, which can ultimately reduce the effectiveness of the plant protection products (PPPs). The authors suggest that optimizing the time at which the PPPs are used can help increase this effectiveness. The ideal fungicide application will be dependent on the specific disease and crop, since climate and atmospheric change might alter the favorability of the disease in a positive or negative way.
Another type of disease management practice the authors analyzed was the application of biological control<!–[if supportFields]> XE “biological control” <![endif]–><!–[if supportFields]><![endif]–> agents (BCAs). The adoption of this technique is also dependent on the specific antagonistic organism’s reaction to temperature and atmospheric change. Some studies imply that pathogens may be favored under these changes, while other studies suggest the antagonistic organism might be favored.
Adopting integrated pest management (IPM) as a management practice was also researched in this review. IPM is a preventative strategy whose main goal is long-term effectiveness of preventing plant disease. It uses a combination of other strategies such as “…biological control<!–[if supportFields]> XE “biological control”<![endif]–><!–[if supportFields]><![endif]–>, use of resistant cultivars, habitat management and cultural practices (108).” Juroszek et al. recommend models be used to predict the long-term consequences in order to adopt the ideal IPM.
The authors ultimately suggest that the ideal disease management strategy must be implemented given the specific plant, pathogen, and environmental factors. They find that disease-forecasting models will be key in analyzing this based on the effect of climate and atmospheric change on plant disease instance and severity.

Impact of Higher Atmospheric CO2 Concentrations on Tree Diseases

McElrone et al. (2010) studied the ways in which higher atmospheric CO2 concentrations, as well as variance in precipitation and temperature, are expected to affect plant diseases. The authors specifically analyzed Cercospora<!–[if supportFields]> XE “Cercospora” <![endif]–><!–[if supportFields]><![endif]–> leaf spot diseases affecting two deciduous trees: sweetgum (Liquidambar styraciflua<!–[if supportFields]> XE “Liquidambar styraciflua” <![endif]–><!–[if supportFields]><![endif]–>) and redbud (Cercis canadensis) trees. Their experiment was conducted at the Duke Forest Free-Air CO2 Enrichment (FACE) facility located in Duke Forest, North Carolina. Cercospora liquidambaris<!–[if supportFields]> XE “Cercospora liquidambaris” <![endif]–><!–[if supportFields]><![endif]–> and Cercospora cercidicola<!–[if supportFields]> XE “Cercospora cercidicola” <![endif]–><!–[if supportFields]><![endif]–> were found to be the leading pathogens infecting the redbud tree and the sweetgum tree respectively; these spot diseases affect the trees by causing lesions on the plants’ leaves. Moreover, the authors determined disease incidence and severity by analyzing a sample of random leaves. A chlorophyll fluorescence imaging analysis and leaf chemical analysis were also conducted to determine the affect of CO2concentration on these disease parameters. The results varied with the differing climatic factors. Because these diseases affect several crops that are economically significant, the results of the present study can be instrumental in implementing management strategies. —Daniela Hernandez
McElrone, A., Hamilton, J., Krafnick, A., Aldea, M., Knepp, R., DeLucia, E., 2010. Combined effects of elevated CO2and natural climatic variation on leaf spot diseases of redbud and sweetgum trees. Environmental Pollution 158, 108–114.

The researchers randomly sampled about 174 to 336 leaves per year from the different experimental plots. McElrone et al.’s experiment was conducted over the years 20002001 and the year 2005. The incidence of the diseases was found by analyzing the percentage of leaves infected. The severity of the diseases, however, was found by analyzing the percentage of leaf area affected and by calculating the lesion area. Observable lesions on the sample leaves accounted for disease incidence. Disease severity was analyzed by measuring the areas of the lesions using ASSESS: Image analysis software for plant disease quantification.
The Duke Forest FACE facility used in this experiment operates by surrounding experimental plants with rings of CO2emitters, which allow concentrations of CO2 within the rings to be controlled. The trees analyzed in the present study were planted in 1998 and placed into sub-plots of the FACE rings. For the purposes of this experiment, the trees were grown under both elevated CO2 and ambient conditions in the FACE facility. The natural precipitation and temperature in the site were left unaltered. The effect of CO2 levels on the plant diseases was determined through a chlorophyll fluorescence analysis and through a chemical analysis, using leaves from the plants to test this effect.
McElrone et al. found that lower than average temperatures cause a greater disease incidence in sweetgum. Additionally, the results showed that there was a greater Cerspora leaf spot disease incidence during wetter years particularly evident in the sweetgum tree. Conversely, the years that faced lower than average precipitation, demonstrated lower disease severity in the rosebud and a lessening of leaf lesions in both tree species. Taking into account the instances in which the plants were significantly affected, the authors found that both disease incidence and severity were favored under the higher CO2conditions.
However, the authors found that there was no significant change in the leaf chemistry among the plants grown under the differing CO2 concentrations. Through the chlorophyll fluorescence imaging analysis, McElrone et al. also concluded that although the plants might experience an increase in Cercospora<!–[if supportFields]> XE “Cercospora” <![endif]–><!–[if supportFields]><![endif]–> leaf spot disease under higher CO2 levels, the net effect is offset by the increase in photosynthetic activity by the uninfected leaf area. The authors suggest further research be conducted to analyze the effect that both the atmospheric CO2 concentration and the resulting climate changes have on these diseases.

A Review on the Impact of Climate Change on Diseases Affecting Tropical and Plantation Crops

Ghini et al. (2011) reviewed and researched the effect of climate change on disease epidemics of coffee, sugarcane, eucalyptus, cassava, citrus, banana, pineapple, cashew, coconut, and papaya. The authors explain the importance of analyzing crop diseases specifically in the tropics because of this ecosystem’s unique conditions. Projections show that although the tropics are expected to experience only a slight increase in temperature, the impact will be of greater magnitude than in other ecosystems. Insect species living in these tropical areas, for example, tend to live under optimal temperatures so that a small increase in temperature would, therefore, have a significant impact on the viruses and disease that are generally transmitted by these insects. The authors found that the impact of diseases on these crops depends on host-pathogen interactions and it therefore varies significantly from one disease to another. The authors promote further research in the subject as well as further research in disease management strategies.—Daniela Hernandez
Ghini, R., Bettiol, W., Hamada, E., 2011. Diseases in tropical and plantation crops as affected by climate changes: current knowledge and perspectives. Plant Pathology 60, 122–132.

Using historical data and projections from models, the authors of a previous study found that under the A2<!–[if supportFields]> XE “IPCC A2 scenario” <![endif]–><!–[if supportFields]><![endif]–> and B2<!–[if supportFields]> XE “IPCC B2 scenario” <![endif]–><!–[if supportFields]><![endif]–> IPCC<!–[if supportFields]> XE “Intergovernmental Panel on Climate Change (IPCC)” <![endif]–><!–[if supportFields]><![endif]–> scenarios the number of monthly coffee nematode and leaf miner generations is expected to increase in Brazil<!–[if supportFields]> XE “Brazil” <![endif]–><!–[if supportFields]><![endif]–>. The increase in generations will thus cause an increase in the pathogen and insect infestation of coffee crops. An experiment cited by the authors also shows that increasing CO2 levels will generally cause a decrease in the latent period of coffee leaf rust. This disease is caused by the fungus Hemileia vasatatrix<!–[if supportFields]> XE “Hemileia vasatatrix” <![endif]–><!–[if supportFields]><![endif]–> and is a serious threat to coffee crops in the tropics; the shortening of latent period for this disease is therefore also of great concern.
Some studies predict that the spread of several sugarcane diseases, such as smut and leaf scald disease, are expected to remain unaffected by climate change because of the systemic nature of these diseases. Other studies, however, project that increases in natural disasters caused by climate change will result in an increase in diseases like leaf scald. Conversely, an increase in temperature is expected to cause a decrease in the severity of other diseases such as pineapple disease since it thrives best in cooler soil temperatures.
Ghini et al. also found that certain diseases affecting eucalyptus are expected to increase in severity. Diseases spread by Ralstonia solanacearun<!–[if supportFields]> XE “Ralstonia solanacearun” <![endif]–><!–[if supportFields]><![endif]–>, Xanthomonas<!–[if supportFields]> XE “Xanthomonas” <![endif]–><!–[if supportFields]><![endif]–> sp., and Quambalaria eucalypti<!–[if supportFields]> XE “Quambalaria eucalypti” <![endif]–><!–[if supportFields]><![endif]–>, for example, thrive under higher temperatures; global warming, therefore, would augment the spread of these diseases. The incidence of secondary pathogen infection to eucalyptus is also expected to increase due to changes in both temperature and precipitation.
When researching the cassava crop, the authors found some general trends linking temperature and bacterial blight epidemics. The data show that in areas whose temperatures are above the optimum range for the bacteria<!–[if supportFields]>XE “bacteria”<![endif]–><!–[if supportFields]><![endif]–>, which is about 22–26 ºC, increasing temperatures will either have no effect or cause a decrease in blight incidence. Conversely, in areas where the temperatures are below the optimum, an increase in temperature will likely cause an increase in blight incidence.
In citrus crops, the data suggest that black spot and floral rot would increase in severity as a result of increasing temperatures.
For bananas, studies show that under both the A2<!–[if supportFields]> XE “IPCC A2 scenario” <![endif]–><!–[if supportFields]><![endif]–> and B2 scenario<!–[if supportFields]> XE “IPCC B2 scenario” <![endif]–><!–[if supportFields]><![endif]–>s, the severity of black Sigatoka, one of the diseases that greatly affects banana yield, will decrease in Brazil<!–[if supportFields]> XE “Brazil” <![endif]–><!–[if supportFields]><![endif]–>. Predictions of a decrease in humidity will likely cause a decrease in the area in which the disease can thrive. Conversely, the incidence of Panama disease is expected to increase. An increase in temperature and a decrease in precipitation are expected to magnify the aggressiveness of the pathogen that causes Panama disease, Fusarium oxysporum f. sp. cubense<!–[if supportFields]> XE “Fusarium oxysporum f. sp. cubense” <![endif]–><!–[if supportFields]><![endif]–>.
As for pineapple, Ghini et al. note that disease occurrence and severity will also vary with climate change. An increase in temperature and decrease in precipitation is expected to lessen the severity of pineapple fusariosis, which is spread by Fusarium subglutinans<!–[if supportFields]> XE “Fusarium subglutinans” <![endif]–><!–[if supportFields]><![endif]–>. Pineapple mealybug  wilt, however, is expected to be increased in severity by warmer temperatures.
Literature on the subject also shows that climate change will create favorable conditions for powdery mildew to infect cashew crops in Africa<!–[if supportFields]>XE “Africa” <![endif]–><!–[if supportFields]><![endif]–> and Brazil<!–[if supportFields]> XE “Brazil” <![endif]–><!–[if supportFields]><![endif]–>. Conversely, projections demonstrate an increase in anthracnose infections, which is the most significant disease that affects cashew cultivated in Brazil. 
For coconuts in Brazil<!–[if supportFields]> XE “Brazil” <![endif]–><!–[if supportFields]><![endif]–>, projections suggest that climate change will cause a decrease in severity of black leaf spot, phytomonas wilt, and heart rot epidemics; leaf blight, however is expected to increase in impact.
For papayas, an increase in temperature will lead to a decrease in yield caused by papaya ringspot virus.
The effect of climate change on diseases in topical and plantation crops is not fully understood yet because there are few empirical data on the subject. Moreover, it is difficult to project the disease management strategies that would be necessary to mitigate crop infections. Additionally, little information is known about the impact that climate change will have on biological control<!–[if supportFields]> XE “biological control” <![endif]–><!–[if supportFields]><![endif]–> of pests. In order to minimize loss in yield of tropical and plantation crops and to understand climate change impacts, Ghini et al. propose future research be conducted.

The Effect of CO2 and O3 Levels on Soybean Diseases

This experiment analyzed the effects that a change in the atmospheric composition will have on the diseases that infect soybean<!–[if supportFields]> XE “soybeans” <![endif]–><!–[if supportFields]><![endif]–> crops. Specifically, Eastburn et al. (2010) researched the implications associated with an increase in CO2 and O3<!–[if supportFields]> XE “ozone, O3″ <![endif]–><!–[if supportFields]><![endif]–> levels, comparing these results to ambient conditions. The three soybean diseases observed were brown<!–[if supportFields]> XE “brown” <![endif]–><!–[if supportFields]><![endif]–> spot, downy mildew, and sudden death syndrome (SDS). The results showed that, throughout the span of the study, both an increase in CO2 and a combined increase in CO2 and O3 are expected to cause a decrease in downy mildew severity but an increase in brown spot severity. However, the different atmospheric conditions did not have a significant effect on either the brown spot or the sudden death syndrome incidence. The data also showed that higher levels of precipitation lead to greater downy mildew severity. Generally speaking, warmer conditions exacerbated both brown spot and downy mildew severity, but chemical analysis showed no change in the structural and chemical composition of the soybean.—Daniela Hernandez
 Eastburn, D., Degennaro, M., Delucia, E., Dermody, O., McElrone, A., 2010. Elevated atmospheric carbon dioxide and ozone<!–[if supportFields]> XE “ozone, O3″ <![endif]–><!–[if supportFields]><![endif]–> alter soybean<!–[if supportFields]> XE “soybeans” <![endif]–><!–[if supportFields]><![endif]–> diseases at SoyFACE. Global Change Biology 16, 320–330.

Eastburn et al. conducted the present study throughout a three-year time span from 2005 to 2007. The researchers did not want to discount the effects that certain climatic parameters might have on the soybean<!–[if supportFields]> XE “soybeans” <![endif]–><!–[if supportFields]><![endif]–> diseases. Instead of growing soybeans under controlled conditions, they, therefore, used the soybean free air concentration enrichment facility, SoyFACE, located on the University of Illinois campus, in which conditions such as temperature and precipitation could occur naturally. The four atmospheric composition conditions tested in the present study were: ambient conditions, elevated CO2, elevated O3<!–[if supportFields]> XE “ozone, O3″ <![endif]–><!–[if supportFields]><![endif]–>, and a combination of elevated CO2 and O3 levels. Conditions were measured regularly to calculate the adequate level of CO2 and O3 that the plants needed to be exposed to.
The authors conducted random samplings of the soybean<!–[if supportFields]> XE “soybeans” <![endif]–><!–[if supportFields]><![endif]–> plants in the varying plots. They tested leaves of those plants showing signs of infection to see whether the diseases (brown<!–[if supportFields]> XE “brown” <![endif]–><!–[if supportFields]><![endif]–> spot, downy mildew, and sudden death syndrome) were the actual cause of the symptoms. Brown spot disease affects plants by causing brown spots bounded by chlorotic tissue on the leaves. The symptoms of downy mildew show up as spots on the top surface of leaves and lesions on the bottom surface. Although sudden death syndrome is actually a root disease, the leaves also show spots when infected.
To quantify the effect of atmospheric changes on the soybean<!–[if supportFields]> XE “soybeans” <![endif]–><!–[if supportFields]><![endif]–> diseases, both disease incidence and severity were measured through visual inspection and a digital image analysis (ASSESS: Image analysis software for plant disease quantification), respectively. Disease incidence was measured as the positive or negative infection of the plant and number of lesions, calculated as a percentage. Severity, however, was quantified by measuring the proportion of the leaf area that was infected as well as the individual lesion size, again calculated as a percentage. Because they are a way of understanding plant defense, cuticle wax as well as carbon and nitrogen<!–[if supportFields]> XE “nitrogen” <![endif]–><!–[if supportFields]><![endif]–> content were measured from the leaf tissue using a chemical analysis. These values offered a further insight as to the impact the diseases had on the soybean.

Soybean is an economically and practically significant crop; its use ranges from food products to the production of biodiesel<!–[if supportFields]> XE “biodiesel” <![endif]–><!–[if supportFields]><![endif]–>. Therefore, it is crucial that research be done to expand on current knowledge of the effect of climatic and atmospheric change on the crop and to implement future management strategies.

A review on the impact of climate change factors on wheat, rice, soybean, and potato diseases

Luck et al. (2011) conducted a review of the impact of climate change on diseases that affect wheat, rice, soybeans, and potatoes. Because these crops are a key source of food and oil, understanding the factors that affect their availability is crucial. The authors found that the relationships between climate change, pathogens, and host crops vary among crop type and the location in which they are cultivated. Additionally, the data show varying crop responses to differing climate change factors such as precipitation, temperature, storm frequency, and atmospheric CO2 levels. The authors conclude that further research is warranted to gain a deeper understanding of the complex relationship between climate change and plant disease incidence. —Daniela Hernández­
Luck, J., Spackman, M., Freeman, A., Trebicki, P., Griffiths, W., Finlay, K., Chakraborty, S., 2011. Climate change and diseases of food crops. Plant Pathology 60, 113–121.

The authors suggest that an increase in temperature will negatively affect the wheat stripe rust-causing pathogen, Puccinia striiformis (Pst). Data gathered from China between the years 1950 and 1995 showed that an increase in temperature caused a decrease in Pst infection. Moreover, this correlation shows that an increase in temperature is projected to cause a general decrease in wheat yield. The slowest warming projections predict a 25–44% decrease in wheat yield, whereas the fastest warming projections predict a 60­–­­­79% decrease in wheat yield. Additionally, changes in precipitation are expected to affect wheat diseases. Wet cool summers, for instance, are expected to create more favorable conditions for aphids that will ultimately intensify the spread of yellow dwarf viruses.
          The data gathered on rice diseases show how different climate factors affect epidemics in different ways. In general, rice blast, a disease caused by the pathogen Magnaporthe grisea, is expected to increase under most scenarios, with temperature change being the most influential factor. In cool subtropics, increasing temperature was shown to cause an increase in the rice blast severity; however, an increase in temperature also showed a decrease in rice blast epidemics in warm/cool humid subtropics. The effect of CO2 changes on rice crop diseases was also observed. The data show that rice grown under higher levels of CO2 has more severe leaf blast epidemics; conversely, panicle blast incidence remains unchanged under the same conditions.
The literature on the subject also points out that an increase in the frequency of storms, caused by climate change, will result in an increase in the dispersal of plant pathogens. Luck et al. researched this correlation through data focused on soybean crop diseases. Hurricane Ivan, for example, introduced Phakopsora pachyrhizi to Louisiana and succeeded in spreading it throughout eight different states. This pathogen affected the soybean crops by causing Asian soybean rust on the plant. Another severe storm, hurricane Wilma, was linked to the dispersal of the pathogen, Xanthomonas citri. This pathogen attacked citrus orchards and spread throughout the state of Florida. Thus the researchers found that climate change factors will not only affect pathogens biologically, but will also affect their dispersal.
          Luck et al. indicates that climate change is expected to cause a general decrease in potato yield by 18–32%. Moreover, the actual effect on the potato diseases will vary among the climate factors. An increase in CO2 levels, for example, is predicted not to cause a significant change in early blight incidence caused by the pathogen, Alternaria solani. Furthermore, data also show that an increase in temperature coupled with changes in precipitation will increase the potato crops’ susceptibility to bacteria such as Pectobacterium carotovorum and Pectobacterium chrysanthemi.
The present research conducted by Luck et al. briefly reviewed changes in some of the most pressing diseases that affect wheat, rice, soybeans, and potatoes; the effects of climate change on these diseases were also reviewed. Since there are several climate parameters that can affect pathogens, the authors suggest more experiments be conducted measuring the severity and dispersal of crop diseases under a combination of these factors. Moreover, they also recommend data be collected to take into account the effect of disease management practices on pathogens. 

The effect of climate change on winter oilseed rape diseases

Both phoma stem canker and light leaf spot are diseases that currently affect the production of oilseed rape crops cultivated in the United Kingdom. Evans et al. (2010) researched the effect of climate change on future projections of these diseases and the yields of this crop. The researchers found that the canker thrives in hotter temperatures. They also noted that the light leaf spot disease generally prefers a cooler and wetter climate. Climate change, therefore, is expected to affect the yield of fungicide-treated oilseed rape crops differently based on the two diseases. The authors predict that there will be an increase of phoma stem canker severity on yields and a decrease in yield loss as a result of the light leaf spot disease. The authors validate these predictions and suggest further research to fully understand the effect of climate change on phoma stem canker and light spot disease that affect the oilseed rape crop.—Daniela Hernández­
Evans, N., Butterworth, M., Baierl, A., Semenov, M., West J., Barnes, A. Moran, D., Fitt, B., 2010. The impact of climate change on disease constraints on production of oilseed rape. Food Security 2, 143–156.

For their research, the authors created five different climate scenarios: baseline, 2020s low CO2 emissions, 2020s high emissions, 2050s low emissions, and 2050s high emissions. The scenarios were based on projections they gathered from sources such as the UKCIPO2, the HadCM3, and the IPCC. Using these scenarios, Evans et al. produced the following weather data for fourteen different areas in the United Kingdom and projected it for thirty years: daily minimum temperature, daily maximum temperature, daily rainfall, and daily solar radiation. The researchers then used these data as the parameters for three already established models; the first model projected the yield of oilseed rape treated with fungicide, the second looked at the severity of phoma stem canker on oilseed rape, and the third predicted the occurrence of light leaf spot on oilseed rape. The models were adjusted to reflect United Kingdom particularities and were then employed to investigate the effect of climate change on the two oilseed rape diseases.
The authors measured the damaging effects of the phoma canker disease on the crop by quantifying the yield loss of the oilseed rape. To find out how much was lost, they compared the total fungicide-treated crop yield to the untreated crop yield when infected by the disease. Evans et al. also investigated the impact of climate change on light leaf spot incidence. They used these projections to estimate yield loss caused by the disease. The results projected that there will be a significant increase in the severity of phoma stem canker disease infection throughout the UK. Conversely, it was shown that there will be a decrease in infection of the oilseed rape by light leaf spot. Overall, however, the researchers found that there will be a notable yield loss caused by the combination of the diseases on the yield of the crop. To fully understand the total scope of the yield loss, both diseases were taken into consideration, showing that the positive correlation between the decrease in light leaf spot occurrence and climate change will not offset the negative results of phoma stem canker without the use of fungicides.

However, the authors found that climate change will increase oilseed rape yield in fungicide crops; this trend is expected for all the climate scenarios. The greatest increase in crop yield is projected to result from the high CO2 scenario, and is thought to be especially true in eastern Scotland and northeastern England. Furthermore, Evans et al. also investigated the predicted economic costs involved, ceteris paribus, with the change in treated oilseed rape yield predicted as a result of climate change. The predicted decrease in yield caused by the phoma stem canker and light leaf spot diseases is expected to counter the predicted increase in the treated oilseed rape yield caused by the climate changes. Therefore, the UK is expected to face a low economic cost for the treated crop. Further research is warranted to have a more complete understanding of the costs involved and the effects these diseases will have on crop yields.

The effect of climate change in the anthesis of winter wheat in the United Kingdom and the resulting impact on fussarium ear blight incidence

Fussarium ear blight is one of several diseases that affect the winter wheat crop cultivated in the United Kingdom. Madgwick et al. (2010) investigated the impact of climatic changes on the flowering period, or the anthesis, of the winter wheat and the effect this anthesis change has on fussarium ear blight incidence. The authors researched this question by constructing two models: one that projects anthesis dates, also referred to as the Sirius Model, and another that projects fussarium ear blight. To develop the Sirius model, Madgwick et al. gathered weather parameters as well as sowing dates for the wheat. In order to create the fussarium ear blight model, the researchers observed weather parameters in addition to the observed anthesis dates. The research showed that climatic changes will progressivly shorten the anthesis date for the wheat and this in effect will increase the incidence of fussarium ear blight. The increase in infection can ultimately have a significant impact on this crop’s availability; therefore, Madgwick et al. suggest further research.—Daniela Hernández
Madgwick, J., West, J., White, R., Semenov, M., Townsend, J., Turner, J., Fitt, B., 2010. Impacts of climate change on wheat anthesis and fussarium ear blight in the UK. European Journal of Plant Pathology published ahead of print January 04, 2011,doi:10.1007/s10658-010-9739-1

Madgwick et al. created a model, known as the Sirius model, based on different weather and sowing parameters to predict anthesis dates of winter wheat in the United Kingdom. The specific weather data gathered to extrapolate the model were temperature, rainfall, and solar radiation, measured in ˚C, mm, and MJ d¯1 respectively. The researchers gathered the weather data from several weather stations to complete the gaps of missing information. Sowing dates for the winter wheat were also collected. The predicted anthesis dates based on this model were then plotted against observable anthesis dates to find the correlation, if any, between these two sets of data. The observable anthesis dates were based on information from the time period of 2003 to 2008 for two regions: southern England and northern England. The plotted data showed that there was a general correlation between the predicted anthesis dates based on the Sirius model and the actual observed anthesis dates, thus validating the purposefulness of the model.
          In conjunction with the Sirius model, the authors also created a model for fussarium ear blight in winter wheat grown in the United Kingdom. Based on similar parameters used for the anthesis dates, the weather data investigated to create the predictions were: minimum and maximum daily temperatures (˚C) and total rainfall (mm). Additionally, the observed anthesis dates for crops in northern and southern England were gathered. Using these sets of data, and an equation derived by the researchers, a model was created for the prediction of winter wheat crops infected by fussarium ear blight. The authors then compared these predictions with the actual observed cases of the crop disease during the time period of 2004 to 2008. The comparisons did not show an immediate relationship; however, the authors attribute this to the fact that there were some inconsistencies in the weather data that this model could not mitigate. Moreover, the researchers note that this model can still be useful in showing some general trends for projections of the impact of climate change on fussarium ear blight.
          Both the Sirius model and the fussarium ear blight model were used to extrapolate predictions for the future. The authors found that the dates of anthesis will become increasingly earlier throughout the United Kingdom; their model projects 11–15 day earlier anthesis dates. Of significant interest is the fact that the impact of climatic change will ultimately be larger in the southern regions of the United Kingdom than the northern regions. The fussarium ear blight model predicts an increase in crop disease infection caused by the shortening of the anthesis date. It also predicts that by the year 2050, the severity of fussarium ear blight will be greatest in the southern regions of England.
          With their projections of faster anthesis dates of winter wheat based on climatic changes, and the resulting increase in percentage of crop infection by fussarium ear blight, the authors suggest further research in this topic. In light of issues related to food security, they ultimately validate the importance of the construction of models that demonstrate the relationship between weather parameters and disease infection on crops.

Climatic Changes in Sweden Cause an Increase in Crop Diseases

Roos et al. (2010) surveyed the effects of climatic changes on plant diseases and pests of various crops in Sweden. The crops investigated include: Brassica crops, cereals, potatoes, sugar beets, and tomatoes. Traditionally, the climatic conditions in this region have protected crops from several diseases; the cold winter temperatures have usually prevented the survival of various pathogens. With the increase in average temperatures, however, crops have become increasingly susceptible to pathogenic invasion. The prolongation in the vegetation period, caused by these climatic changes, was shown to be a root cause of the observable increase in disease resilience. Changes in precipitation have also demonstrated negative effects on crops. In their study, the authors observe the increasing damage in crop health caused by global warming, projecting an increase in severity in the future. Furthermore, Roos et al. promote further investigation in preventative strategies, citing options such as genetically modified crops to alleviate the ramifications of increasing temperatures.—Daniela Hernández­

Roos, J., Hopkins, R., Kvarnheden, A., Dixelius, C., 2010. The impact of global warming on plant diseases and insect vectors in Sweden. European Journal of Plant Pathology 129, 9–19.

          Sweden is currently facing climatic changes that have the potential of dramatically altering the integrity of food crops. Studies have shown that the region is expected to experience a higher temperature change than the global mean change. Roos et al., ­at the Swedish University of Agricultural Sciences, project that these changes will ultimately alter vegetation periods. A temperature increase of 4oC is predicted to cause an increase of one to two months in the longevity of the vegetation period; it is also predicted that in the southern regions the change could be up to three months. The projection for the southern regions is of special interest since the bulk of crops grown in Sweden, is done so in the southern temperate zone. The climatic changes are also expected to lead to an overall increase in rainfall during the winter, which could ultimately affect crop health. Due to the recurring freezing and thawing processes these environmental changes would result in, plant roots are expected to undergo severe damage. The damages to the roots could essentially make the crop susceptible to pathogenic invasion. Furthermore, the authors conclude that although a certain crop might be better adapted to withstand winter conditions, the crop might not be able to survive the added stresses caused by the climatic change.
          The increase in longevity of the growing season, coupled with the changes in precipitation suggests that Swedish crops will increasingly become more vulnerable to disease and pests. For example, wheat and barley are expected to face an increase in attack by some rust diseases, such as brown and yellow rust, caused by the prolongation of the vegetation period. Additionally of great concern, is the potato disease, late blight, which is caused by the oomycete, Phtophthora infestans. Trends of higher temperatures and increased humidity are expected to create favorable conditions for late blight to thrive in. The authors also suggest that an increase in mean temperature will result in an increase in the number of insects, which will result in an influx of different kinds of pathogens.
Roos et al. recommend an overall increase in measurements for protecting crops against the ramifications of global warming. To mediate the damaging effects of diseases on crops caused by climatic changes in Sweden, the authors suggest further development in genetically modified crops that can withstand pathogenic aggression. Additional research is warranted to decrease the dependency on pesticides in order to protect crops against disease, and thus also decrease the risk of potential damages to human health.