By Beatrice Hawkins
As I drove out west in NSW recently I saw the effect of biological control on prickly pear infestations. The introduction of cactoblastis must have been am amazing relief to farmers in the western areas. It is certainly one of the most successful incidents of biological control known in Australia.
Some other attempts at biological control have not been so successful. Notably the cane toad that was introduced in 1935 to control cane beetles. We all know that this has in itself become an environmental nightmare with the toads spreading far and wide and having a disastrous effect on out native wildlife.
Cacoblastis however, has remained host specific and enabled huge areas of western land to once again become productive. In Dalby I believe there is a monument to the moth that was introduced in the 1920’s.
Like so many other things that have been introduced into Australia and have become a problem, there was what was considered, at the time, a valid reason for its importation.
In other countries it is used as a natural fence barrier as nothing will tackle crossing it. It is also host to the cochineal insects and an attempt to establish a cochineal dye industry was another reason for bringing it here.
At the time Spain had a worldwide monopoly on the production of the valuable red dye. It was the red dye used for the British Army “Red Coats” and so Britain thought it a good idea to establish their own industry in the new colony in Australia!
Cochineal insect infested prickly pear was first brought here from Brazil by Captain Arthur Phillip. Apart from the original “Opuntia monocantha” about 25 other species have found their way here, probably as garden cactus specimens.
After reading about it, it is my belief that the control that I noticed in my drive, is the cochineal insect at work. While cactoblastis was the main control, cochineal insect was also released and was effective in some areas.
In 1900 an area of approximately 10 million acres of South Queensland and western N.S.W. had been made useless by the infestation and this increased very rapidly until it is estimated that in 1925 the area was greater than 60 million acres, with the increase in some years, being in excess of 2.5 million acres. Now I am not a mathematician, but I have also read another report that said the estimated area covered was 240,000 sq kms, equivalent to the size of the United Kingdom!!
After many attempts at control with fairly deadly chemicals and attempts at cutting down, burning, rolling and various other unsuccessful methods, the cactoblastis caterpillar was released in 1926 and is still recognised worldwide as the most successful biological control ever.
It was not an overnight success with huge numbers of the caterpillars bred and released, especially from the Chinchilla Field Station, but within 6 years most stands of the pest had been eradicated. Land that had been declared useless for any agricultural use was now able to be reclaimed and farmed.
The spread of the pear in Australia has also been of interest world wide as it originates from areas of Texas and Florida with rainfall of 40-50 inch average but the areas where it spread here were of much lower rainfall.
So much for your history lesson!
I have also found many other interesting uses for this noxious pest.
Apparently the fruit is very nutritious and each fruit can contain about 150-300 seeds. The seeds are very tiny and only contain about 5% oil. This oil apparently will make us all look years younger but it takes about 1 tonne of fruit to produce one litre of oil in a fairly labour intensive process so is quite expensive.
Research tells me that prickly pear can also be used in medicine as a control for type 2 diabetes, high cholesterol, obesity, alcohol hangover, colitis, diarrhoea, and benign prostatic hypertrophy! It can also be used to fight viral infections – truly a plant of many uses!
Now this information is all from “google” and I can’t vouch for its accuracy or veracity but it makes for interesting and entertaining reading if you look it up.
Apparently it has been a staple of Mexican and Central American cooking for thousands of years. I think they must have been very hungry to even try it in the first place!!
Three parts are edible: the pad (leaf) as a vegetable, the flower petals as a garnish or added to salads and the fruit to be eaten as any other.
The fruit can be mashed and boiled down with sugar to make a dark red syrup, it can be turned into a jelly and a recipe for “margarita jelly” was found – this included lime juice and zest, orange zest and tequila! The Mexicans are good at using cactus as tequila is made from the Agave plant, another desert cactus.
I hope everyone is staying well and, after the frantic run on the supermarkets, has enough of everything to see this situation to its close. Stay away from people as much as possible and stay well.
*This is an old article that has been digitised so our readers have access to our full catalogue.
