North West Weeds
Your local guide to local noxious weed control (NSW, Australia)
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North West Weeds |
Origin│ Description │ When to use │How to distribute│ More information │ Disclaimer Biological control of prickly pear has been one of Australia's success stories when it comes to weed control. And, biological control continues to play a very significant role in controlling prickly pear species in New South Wales, particularly in the drier, warmer areas.
The Cactoblastis success story The success of cactoblastis is still regarded as the world's most spectacular example of effective control of a weed by biological means. The
origin of Cactoblastis DESCRIPTION OF CACTOBLASTIS Moth
Larvae When the tiny larvae hatch, they move to a
nearby point on the plant and then
work as a team to "chew" a small hole through the tough, outer layer of the
plant leaf/pad. The tiny larvae "form a circle" and take turns to nibble
at the selected site until eventually they work their way through the outer skin
and into the soft, edible interior of the plant. As one would imagine, the tiny
larvae work quickly to enter the plant as quickly as possible - while out in the
open they are very vulnerable to ants,
The larvae feast their way through the plants for some weeks before retiring. By this time they are 25mm long. They actually leave the plant and shelter under dead leaves or other rubbish at the base of the plant. They then spin their cocoons, later emerging as a moth to start the whole process again. [NB Another, similar-in-appearance, larvae can sometimes be found. Slightly smaller, and a paler version of cactoblastis, Tucamania tapiacola was also introduced into Australia to help control prickly pear. It never had the same impact as cactoblastis, but it's still out there, annoying the prickly pear.] Cactoblastis have their enemies. Ants are the biggest threat, especially when they attempt to move from one plant to another. For this reason, the winter generation of Cactoblastis seems to have the best results in northern New South Wales because of the reduced ant presence. WHERE AND WHEN TO
USE CACTOBLASTIS? "When" to use Cactoblastis? There are two cycles per year, so there is no real time barrier. The main thing is to keep a number of prickly pear stacks around the property to encourage the moths to call and deliver their eggs. Cactoblastis is mainly used for control of common pest pear (Opuntia stricta spp.). In some seasons they will also significantly reduce the bulk of individual tiger plants (very rare for them to destroy the whole plant, and unless cochineal is also present, the cacto often creates a bigger mess because there are more loose tiger pear segments on the ground). Cactoblastis assists with control of velvety tree pear by decimating seedling growth. MEANS OF DISTRIBUTION Transferring eggsticks to new plants was the method originally used to distribute cactoblastis to new areas. The job involved pasting the eggsticks to small pieces of paper and attaching them with a pin to new plants. We find that, generally, this is unnecessary because the moths are periodically moving through the pear areas and will lay their eggs on new plants if they find them. Cochineal is the other valuable prickly pear biological control agent. Also please return to Weeds List to access information on biological control for individual plant species like tiger pear, velvety tree pear, common prickly pear. Also please check out Prickly Pear History. "Prickly-pear Pest in NSW" by VH Gray, Prickly-pear Commissioner 1951-1980.
DISCLAIMER:
The information contained in this web site is based on
knowledge and understanding at the time of writing. However, because of
advances in knowledge, users are reminded of the need to ensure that
information upon which they rely is up to date and to check currency of the
information with the appropriate officer of North West Weeds or the user’s independent adviser. |
Send mail to
northwestweeds@aapt.net.au with questions or comments
about this web site.
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