Biological battlers: Tiny insects help control weed outbreaks in Far West NSW

The NSW Government is unleashing biological control agents to help manage outbreaks of invasive weeds across reserves in Far West NSW.

Crown Lands has been propagating cochineal, a tiny scale insect, to attack invasive cactus species, including Hudson pear, common pear and devil’s rope in the Cobar, Walgett and Wentworth districts.

Cochineal insects are native to South and North America and are a natural enemy of the weeds. They are effective in controlling various cactus species by inserting their straw-like mouthparts and feeding on the plants’ sap, causing it to lose water and nutrients, collapse and eventually die.

At Tallebung Reserve, near Condobolin, a colony of the cochineal species (Dactylopius tomentosus) has eliminated about 90 per cent of a large outbreak of devil’s rope (Cylindropuntia imbricata), which if left untreated can form dense thickets that impact agriculture, hinder livestock, compete with native vegetation, and have sharp spines that can harm people, livestock, and wildlife.

Hudson pear (Cylindropuntia pallida) is a Mexican cactus first detected in the Lightning Ridge area in the 1960s. Common pricky pear (Opuntia stricta) was first introduced to Australia in the 19th century, while devil’s rope was first recorded in 1911. All three weeds are extremely prickly cacti that spread easily and have similar impacts on the health and use of land.

Releasing cochineal onto these weeds is an effective control treatment, especially in difficult to reach and environmentally sensitive areas. Supporting chemical treatment, biological control is a long-term, environmentally friendly strategy which is less expensive than chemicals. The insects self-propagate, attaching to nearby cactus plants, killing off large swathes of plants. 

Due to the size of most cactus outbreaks, cochineal colonies alone will not eradicate infestations but can reduce their size considerably ensuring weed control programs are manageable and effective.

Crown Lands Group Leader Property Management Jarrod Smith said:

“The cochineal biocontrol agents are an important tool in managing cactus populations, which can be absolutely devastating to our environment as they spread quickly and can completely overrun land, rendering it unsuitable for grazing and causing real damage to native species.

“It’s great to see that landowners are adopting the use of these insects to help manage their own outbreaks.”

Crown land leaseholder Bill Neyland said:

“We introduced cochineal bugs a few months ago on our leasehold property ‘Wolberton’ north of Pooncarie where we graze sheep and goats to see if it can help remove spiky weeds that are impacting part of our land, so hopefully they can make a difference over time.”

Minister for Lands and Property Steve Kamper said:

“The NSW Government is focused on building better communities so I am very pleased to see Crown Lands managing invasive weeds to maintain our reserves and protect the environment for native plants and animals.

“Crown land reserves are a precious resource and cochineal insects can be a useful ally that can help keep reserves in good health for their intended purposes.”