Too Much Rain, Humidity Promote Disease Outbreaks in Plants

A new study revealed that too much rain, when paired with prolonged high levels of humidity, could promote the development of diseases in plants.

The study, published in the journal Nature, showed that climate conditions could greatly influence disease outbreaks in plants. Furthermore, potential outbreaks of plant diseases could only occur if certain conditions were met.

"What we discovered in this study is that humidity is required for bacteria inside the leaf to accumulate water," explained Xiu-Fang Xin, a research associate at Michigan State University and lead author of the study, in a press release. "Conditions need to be right. That's why we don't see widespread plant diseases every year."

For the study, the researchers looked through past historical weather records to find a correlation between a period of high humidity and disease outbreaks. Citing the devastating outbreak of apple fire blight in west Michigan about ten years ago, the researchers noted that there were rains and long periods of high humidity during the apple blossom season during that year, creating the perfect outbreak of disease that wiped out almost half of the apple crop in the area.

Previously, scientists believe that bacteria can infect plants by suppressing the plant's immune system. However, Xiu-Fang and her colleagues found that some of the most virulent bacteria affecting plants could directly inject a protein in the plants' cells to increase the levels of water content in a part of the plant known as apoplast. Apoplast is the area in the plant where bacteria normally live. High concentration of water in the apoplast can create a watery environment for the bacteria to strive, increasing the prevalence of diease.

With their findings, the researchers hope for the development of certain guidelines that can prevent future outbreaks of diseases in plants. Accurate weather forecasts could be used to determine the extent of rain and humidity, giving farmers some time to apply precautionary measures for the survival of their crops.