Celebrating 90 years since the creation of cactoblastis
A PLANT that grows just about anywhere, holds plenty of water and vitamins, and makes good fodder for cattle sounds just about too good to be true.
Farmers in the late 1800s and early 1900s didn’t think so as they discovered the benefits of prickly pear in weathering tough droughts like the one in 1901-02.
But of course if something sounds too good to be true, it probably is and that was the case with the invasive species, which took over some four million hectares of prime agricultural land across Queensland and northern New South Wales.
The plant was originally introduced to Australia to break the Mexican monopoly on cochineal, which was used to dye the red coats of British soldiers.
But unfortunately, their ability to help farmers weather drought also contributed to them becoming the most widespread invasive weed in Queensland thanks to seeds being spread in manure.
Eradication of the tough pest species by chemical or manual means was estimated at being worth six times the value of the land at the time, leaving landholders in a very prickly situation.
But in 1927, a very special shed was built out near Chinchilla that changed the face of the Queensland countryside.
It’s the kind of corrugated iron shed you might see on many a farm or industrial site, but it was actually very unique.
There is no other shed in Australia (or the world) which can equal its claim to fame and the shed is 90-years-old this month.
It was the first of two built in 1927 to protect cactoblastis cocoons and larvae, which were being bred in a mass breeding program to eradicate the prickly pear which, in the worst places, created a monoculture that left no room for crops or stock.
Two years earlier, a special body called the Prickly Pear Travelling Commission went on an expedition to other countries to find insects that fed and bred on the plant that could be used in a possible eradication program.
More than half a million individual insects which fed and bred solely on cactus or prickly pear were sent back to the Chinchilla Field Station from the Field Stations in USA and South America.
The list included spiders, moths, grubs and more, and eventually scientists found exactly what they were looking
for for so long.
In early 1926, the first trial release of the more than 2,200,000 eggs from 19 locations, 15 in Queensland, resulted in the collapse of the first pear plant to be destroyed in Australia by cactoblastis cactorum in September of that year on a property at Chinchilla.
Chinchilla Field Station was designated as the principal breeding station and it was from here that insects were forwarded, initially, to the other field stations.
There were 250 cages of differing sizes in use on the field station and 2500 overall in the campaign.
The entomologists lived in the house on the property from September 1923 after Alan Dodd oversaw the establishment of the first cages and insectories prior to leaving for Uvalde in Texas, which was the principal field station in USA.
There were 10 entomologists overseas over a period of 19 years from 1920 to 1939 when the campaign ended.
Of the 29 pear species introduced into the country, nine had developed in pest proportions.
John Mann, who received that first shipment of cactoblastis at Sherwood in 1925, was later an officer-in-charge at Chinchilla from 1929 – 1933 while he was the senior experimentalist working on other pear species.
“The introduction of C cactorum changed the whole outlook regarding prickly pear control,” Mr Dodd later wrote.
“Had that one shipment given poor results, one can but wonder to what extent the success of the biological campaign would have been prejudiced, or at least delayed.”
He said if the first shipment had failed, it might well have been years before another expedition was made to Argentina, where the busy little grub was discovered and shipped from.
When the Chinchilla Field Station closed in 1936, the community at Boonarga decided to name their community hall after the insect that gave them back their land.
Thousands of people have driven along the Warrego Hwy passing that heritage-listed structure without knowing that the cactoblastis which it commemorates was bred on the field station 7km away on the other side of Chinchilla.
To honour the work involved in this ecological miracle, a monument consisting of relevant information about the operation of the Chinchilla Field Station was erected by the descendants of the original owner, who himself was involved in the prickly pear program at the Dulacca Experimental Station 1912-15.
On the fence line of the property on Clarks Rd, 7km south west of Chinchilla, the monument is easily accessible through town or from the Warrego Hwy.
The local Lions Club recently completed its project to provide a cover for the display.
This cover is a scaled replica of the shed.
As the entomologists involved have all died and the other field stations have been dismantled, the only remnant from this ecological miracle, the magnitude of which has not been equalled in the world, is –‘ the shed’.
When standing at the monument, the shed is visible near the tree line 100m to the left.