April 2024 Pest of the Month: Edema
12 April 2024
Edema is a physiological disorder caused when plants send more water to cells than can be transpired, as a result the plant cells are damaged, can swell and/or collapse.
Edema symptoms can vary depending on the plant species, cultivar and conditions experienced by the plant. It produces a leaf spot that can be confused with insect pest damage, fungal and bacterial leaf diseases.
Typical symptoms are raised gall-like growths, water-soaked spots and/or sunken lesions. Sometimes multiple symptoms can be observed on the same plant or lesions can be raised and then become sunken.
Many plant species are susceptible to edema, particularly:
- blueberries
- eucalyptus
- mango
- spathiphyllum
- vegetable seedlings
- and many foliage plants.
Edema is most often observed during autumn and spring when day-time temperatures are relatively high and nighttime temperatures are relatively low coupled with high rates of soil moisture.
Plants transpire substantially during the day during these conditions and may continue to send a high volume of water to leaves at night. However, if temperatures are relatively cool the amount of water sent to cells cannot be transpired and cells are damaged.
Other conditions can also cause plants to produce edema symptoms so it is important to correctly identify edema.
Management of edema includes monitoring temperatures and reducing nighttime soil moisture when there are severe temperature fluctuations.
Consider modifying the growing environment that susceptible plants are grown, avoid leaf wetness during high humidity periods and consider growing varietals that are less susceptible to edema where possible.
If you require edema identification, you can send specimens to Grow Help Australia (https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/crops/test/grow-help-australia/tests). Each year, all production nurseries receive six free pest or disease diagnostic samples.
For more information on the biology and management of edema: · visit the Pest ID tool at https://pestid.com.au/login
Read the edema nursery factsheet at https://nurseryproductionfms.com.au/download/edema-and-intumescence-fact-sheet/
Leaf spot symptoms caused by edema can be remarkably variable and include raised gall-like symptoms (left) water soaked spots (middle), and sunken spots (right)
