PESTS within Australia.

As I entered my home State of Queensland at the completion of my recent trip to Vic. & SA I came upon an area which contained a quite substantial growth of "Prickly Pear" this led me to research the subject for this post.

Please click on photos to enbiggen them.

First up, here are some cold hard facts about the infestation of 25 million hectares (thats about 55 million acres) of NSW & Qld. countryside.

Prickly pear first came to New South Wales with the First Fleet. It was to be used to establish a cochineal dye Industry... young cochineal insects feed on the pads of prickly pear. The adults grow to about the size of a "match head" and when squashed produce red colouring.

At that time, Spain and Portugal had a world-wide monopoly on the important cochineal dye industry and the British Government was keen to set up its own source of supply within its dominion. The red dye derived from cochineal insects was important to the western world's clothing and garment industries. It was, for example, the dye used to colour the British soldiers' red coats.

Prickly pear is in our history books as one of the most invasive weeds ever imported into Australia. The spread was helped by gardeners who admired the ease of growth as an ornamental planting.

It had a devastating impact on life in rural eastern Australia during the early part of the 20th century. Special acts of Parliament were passed to enforce control measures in an attempt to halt its spread through Queensland and New South Wales

By 1925, prickly pear was completely out of control, infesting some twenty-five million hectares in New South Wales and Queensland. It was spreading at the rate of half a million hectares a year and nobody could stop its progress!

The answer to the main prickly pear problem came in the form of biological control. As the amazing spread of prickly pear in eastern Australia was considered to be one of the botanical wonders of the world, its virtual destruction by cactoblastis caterpillars (Cactoblastis cactorum) is still regarded as the world's most spectacular example of successful weed biological control. The first liberations of cactoblastis were made in 1926, after extensive laboratory testing to ensure they would not move into other plant species.

Within six years, most of the original, thick stands of pear were gone. Properties previously abandoned were reclaimed and brought back into production.


This historical photo shows how Prickly Pear had adapted to the Australian climate over a century and had become the most invasive noxious weeds found anywhere in the world.


The control measure that finally won the war on Prickly Pear was this small caterpillar which spread through the infested areas like wildfire and brought a quick and highly successful end to the problem.

We have had a few very similar disasters brought to us by the ignorance of the consequences by the early settlers, I will follow up with posts about "rabbits" & "cane toads" very soon.