Grasshopper update for western and north-western Queensland
The not so humble grasshopper has had a significant economic and environmental impact in western and north-western Queensland over the last four years.
In recent weeks, we have seen patches of good rainfall in areas of the north-west. Although we are uncertain of the triggers that initiate hatching of the predominant western Queensland grasshoppers, this combination of rain, day length and temperatures could provide suitable conditions.
The northern and north-western beef and sheep teams from the Department of Agriculture and Fisheries (DAF) have received reports of scattered grasshopper nymphs in isolated areas between Richmond and Julia Creek. There are also observations of adult spur-throated locust around Hughenden, Winton, Muttaburra and Longreach, although numbers are not considered sufficient to cause significant damage at this stage.
We are encouraging producers to keep an eye out for the small grasshopper nymphs (hatchlings) and observe their locations. Increased numbers of birds circling in a certain area may indicate increased insect or grasshopper activity on the ground. If you observe grasshopper nymphs hatching, one option is to intervene early and spot-spray while they are still confined to a smaller area. This presents an opportunity to interrupt their life cycle as well as kill the current population and prevent them causing damage to pasture as adults.
Grasshoppers are less likely to form bands or swarms like the locust species do. Early intervention immediately post-hatching and before the young grasshoppers disperse is a key time to act where practical.
We are monitoring the current situation closely and helping with grasshopper/locust identification as requested, as well as conducting regular and structured on-the-ground surveillance of locust species across the region.
Control options
- Fenitrothion—an Emergency Use Permit is current for Fenitrothion and provides producers with a chemical option to spray.
- Green Guard®—a bio-pesticidal alternative for organically-certified producers and those who prefer biological control.
It is essential that affected producers carefully assess the benefit and cost of applying control options and take into account the direct cost of the control, cost of applying the control, and the expected benefit from treatment.
Grasshopper impact and update survey
The Grasshopper Impact Survey and Update Report is now available.
Fifty-nine grazing businesses participated in this survey to help us capture key impacts across the affected regions.
The total combined cost of grasshoppers to these businesses during the 2020 and 2021 seasons was estimated at $18.3 million. The total area impacted was about 1 308 545 ha, varying between 15 000 and 22 000 ha per property.
The cost to industry comprised increased costs of agistment, transport, supplementary feeding, time, labour and spraying, as well as the opportunity cost of early sales and delayed restocking.
Grasshoppers also had a significant environmental impact through reduction in feed base and ground cover. There was also a mental health impact on producers.
Further research
Further research is required to establish a better understanding of the life cycle and ecology of these grasshoppers. We are currently seeking funding for this research, which will help determine the triggers and ideal conditions for population booms. This would help us predict population density and allow for earlier changes to management facilitating proactive rather than reactive approaches.
The DAF Grasshopper Working Group continues to meet regularly to coordinate activities and provide industry with the most updated information.