Forecasting the grass pollen season


Even though the grass pollen season won't start until sometime in late October, we're already predicting it will be a heavier than normal grass pollen season this year.

But how on earth do we know that?

As it happens one of our best indicators of the coming season isn't actually here on Earth at all but above us in space.


Satellites regularly take images of our planet at various wavelengths of light.  Chlorophyll, the green pigment in plant leaves, absorbs light of particular wavelengths and uses this energy to make food from carbon dioxide and water through a process known as photosynthesis.  Measuring how much chlorophyll there is in a plant is a good way of finding out how healthy it is.

Chlorophyll levels can be measured from satellite imagery using the Normalised Difference Vegetation Index or NDVI, a unit-less ratio that ranges between -1.0 and +1.0.  Positive NDVI values are associated with a greater density and greeness of plants and NDVI values close to 0 or below are associated with bare soil, urban areas and bodies of water.

Today's picture, taken from the Bureau of Meteorology website, shows Victoria's average NDVI for August.

You'll see that large areas of the state are looking pretty green coming out of winter, especially those grazing and cropping areas to Melbourne's west and north.  In short the green areas show that a fair chunk of the state's four million hectares of perennial ryegrass pastures, the source of Melbourne's allergenic grass pollen, is in pretty good health and growing well.

That growth is setting us up for one of the best (or worst, depending on your point-of-view) grass pollen seasons in recent years.

But this outlook isn't locked in.  For instance if September rainfall disappoints there will likely be some reduction to the size of the season.

But with decent spring rains we could be in for quite a season.

Sneezin’ season, TODAY Extra chat to Associate Professor Ed Newbigin about how to cope with hay fever.

Looks like a severe hay fever season this year

Click here for the story in The Age about the coming hay fever season.

Pine and cypress pollen

Aug 19 2016

Yesterday, Thursday August 18, was warm and spring-like here in Melbourne and I'm sure a few people will have experienced some hay fever.  It was windy too and the count, 539 pollen grains per cubic metre, shows that the air was also heaving with pollen.  Although the wattles are flowering profusely at the moment, there was no wattle pollen at all on the slide and most of the pollen was instead from conifers such as pine and cypress.   Personally I think wattles are unfairly blamed for allergies at this time of year.  Their bright yellow flowers draw the eye but it is often the pollen of other, less showy plants that is the real cause of the problems.  These plants include exotic trees such as birch and ash and although we didn't see any of their pollen yesterday either, they'll be flowering soon and I'll be sure to let you know when it is around.

Today's picture shows pine and cypress pollen.  Pine pollen has a main body and two laterally placed air-filled sacs, which help the pollen grain to float on the wind.

Something in the air?

pollen Aug 11 2016

Hi Melbourne, already a touch of spring in the air and I’m excited about the coming pollen season. I’ve had some questions about what’s currently in the air and the answer is not much. Took a count on Thursday Aug 11 and as expected saw no grass pollen and only 7 other pollen types per cubic metre of air. Among the other pollen were pine, cypress, eucalyptus and possibly some plantain as well. A few fungal spores such as the one shown, which I think is Pleospora. There will be a few changes to the pollen count this year which I’ll tell you about later.

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Apart from any use as permitted under the Copyright Act 1968, no part maybe reproduced by any process without prior written permission from
the University of Melbourne, Australia. Requests and inquiries concerning reproduction and rights should be addressed to Associate Professor Ed Newbigin
School of BioSciences, University of Melbourne. Phone: +61 3 8344 4871.