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.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s