Wheel cactus biocontrol

Opuntia robusta Wheel cactus Wheel cactus, along with all species of Opuntia cacti have been declared [Weeds of National Significance](http://weeds.ala.org.au/WoNS/opuntioidcacti/) due to their invasive nature and negative impact on native flora and fauna. Wheel cactus is drought-resistant and found throughout Australia, particularly in southern Australia, north-western and central Victoria. Established cacti can live for several decades and grow densely, hindering growth of native species and harbouring pest animals. In pastures, wheel cactus limits the grazing ability of animals as they avoid grazing due to its sharp bristles. Dense infestations of wheel cacti my also affect human activities and the barbed bristles may cause injury if coming in contact with skin. Two biocontrol agents have been released to control wheel cactus: 1. Cactoblastis *Cactoblastis cactorum* 2. Cochineal scale insect *Dactylopius opuntiae* The combined actions of these two biocontrol ages are expected to contribute to the control of wheel cactus infestations in Australia. Of the two biocontrol agents, Dactylopius has shown the most promising results, having been observed to decrease fruit output in wheel cacti.健壮梨果仙人掌（*Opuntia robusta*，俗称轮盘仙人掌（Wheel cactus））与所有仙人掌属（*Opuntia*）仙人掌物种，因其入侵特性及对本土动植物的负面影响，已被列入《国家重要杂草名录》（Weeds of National Significance，详情见http://weeds.ala.org.au/WoNS/opuntioidcacti/）。 轮盘仙人掌具有耐旱特性，广泛分布于澳大利亚全境，尤以澳大利亚南部、维多利亚州西北部及中部地区最为常见。定植成活的植株可存活数十年，且生长极为密集，会抑制本土物种的生长，并为有害动物提供滋生栖息场所。在牧场中，轮盘仙人掌的尖锐棘刺会导致牲畜避食，从而限制了放牧活动。轮盘仙人掌的密集侵染还会干扰人类生产生活活动，其带倒钩的棘刺接触皮肤后可能造成损伤。 目前已针对轮盘仙人掌释放了两种生物防治天敌（biocontrol agents）：1. 仙人掌螟（*Cactoblastis cactorum*）；2. 胭脂介壳虫（*Dactylopius opuntiae*）。预计这两种生物防治天敌的协同作用可助力澳大利亚境内轮盘仙人掌侵染灾害的防控工作。在两种天敌中，胭脂介壳虫已展现出最为可观的防控效果，观测显示其可有效降低轮盘仙人掌的结实量。