Biosecurity SA has analysed results of a recent locust survey it conducted in the Mid North in conjunction with the Australian Plague Locust Commission.

The survey found the overall locust population in South Australia this autumn is lower and less widespread than at the same time last year. It’s not expected that there will be any adult locust migration into SA this autumn.

The present adult locust population is expected to decline during April and is unlikely to cause any issues during crop sowing.

There have been no confirmed reports of egg-laying. However, some highly sporadic egg-laying from the existing adult population is likely during the remainder of this month and into early April, resulting in scattered mostly low density egg beds.

Some of these eggs will hatch in autumn but most will now enter winter diapause (suspended development) and not hatch until spring. There is no expectation of a significant locust population developing from any autumn hatchings.

The survey covered areas of the Mid North where dense hopper bands were present during February (around the Koolunga/Yacka to Gladstone districts) and also adjacent areas further south from Tarlee, north to Quorn and Hawker, and west to Burra/Yunta/Broken Hill. Separately, the APLC surveyed from Renmark to Burra.

Forecast from autumn to spring

In spring, some highly localised hatching of hoppers can be expected to occur in areas where adults laid eggs in autumn. While the extent of egg-laying is unknown, the spring population is expected to be lower and less widespread than the spring population of 2011.

Any autumn and spring populations should be well within the capacity of landholders to control on individual properties.

Landholders are still encouraged to report any egg-laying activity to Biosecurity SA through the hotline on the above number.

Very few new reports of locusts sighting have been received by the Locust Hotline in the past fortnight. Locusts that were prominent have remained in the same general area of the Mid North, after fledging, in the Georgetown/Narridy to Koolunga/Yacka to Spalding/Washpool districts. Some spread to the Gladstone and Laura districts. This current generation of adult locusts is not expected to pose a risk to crops at sowing.

Biosecurity SA is planning a survey of the current population later this month to determine whether any further populations can be expected in autumn or spring. Egg- laying from the current population, if it occurs, is predicted to be sporadic and highly localised.

We encourage reports of egg-laying behaviour within the next two weeks to assist with our survey and predictions of locust hatchings in autumn and spring.

Biosecurity SA is not expecting any migrations of adult locusts into South Australia as had occurred in 2010. The latest Australian Plague Locust Commission bulletin (see hotlink near top of this page) also provides its assessment of the situation in South Australia with no indication of fly-ins from interstate at this stage.

There has been a small rise in the frequency and number of reports to the Locust Hotline in the last few days as the latest generation of locust hoppers start banding and marching.

Reports in recent days have identified bands of locust nymphs to be confined to a localised area of the Mid North, from approximately Georgetown/Narridy to Koolunga/Yacka to Spalding/Washpool.

A survey through the region by the Australia Plague Locust Commission (APLC) last week confirmed that the locust nymphal population appears to be largely confined to this area. The APLC also reported that most hoppers are in the fourth to fifth instar stage of development and can be expected to start fledging from this week.

Some small localised swarms may develop but this new generation of adults is unlikely to persist long enough to pose a risk to crops during sowing. With conditions becoming increasingly dry, these adults may disperse across districts looking for green feed and could pose a nuisance in paddocks, roadsides or even around some home gardens.

While this new generation is much smaller than populations present at the same time last year, there remains a risk of further localised and small-scale egg-laying by adults if suitable conditions occur. Biosecurity SA is strongly encouraging producers to report any observations of egg laying activity by adult locusts in coming weeks to the Locust Hotline on 1800 833 451, so accurate advice can be presented on the risks ahead of sowing.

Producers also are recommended to undertake spot control on larger patches of locust hoppers where they can, or include an insecticide with summer weed control tank mixes where larger patches are present throughout paddocks. This will help reduce populations and the chance of further populations developing during sowing of crops.

Biosecurity SA thanks producers and the general public for their recent reports which continue to provide valuable intelligence for survey work and advice.

Recent calls to the locust hotline indicate that a new generation of locusts has been observed hatching in a few small patches in the Mid North during mid-January. Locust hatchings may continue to be observed into early next month as a result of egg-laying by adult locusts during December.

Reports to date have identified the new locust hatchings to be in areas around Georgetown, just south of Jamestown, Gulnare, Yatina (north west of Peterborough, between Black Rock and Jamestown) and Narridy (between Gulnare and Crystal Brook) with locusts estimated to be at the second instar stage.

While the number of reports of hatching locusts is very low, producers in the Mid North are encouraged to monitor areas where adult locusts were present or where adults were seen laying eggs in December.

Producers should consider spot spraying any smaller patches of banding locust nymphs, or including an insecticide with any summer weed control spraying that they undertake, where larger or more numerous patches of bands are observed in their paddocks.

Locust nymphs will most likely target green feed. We have received one report of locust nymphs in a lucerne crop.

Chemical resellers have a range of insecticides registered or under permit for use in locust control and landholders should consult their local reseller for advice on the best chemical for their particular situation.

Locust nymphs should be targeted when they start banding (second to third instar stage after hatching) but before they reach the adult stage where they are capable of flying (see the Australian Plague Locusts fact sheet on this site for more information on a locust’s life-cycle). 

It should be mentioned, the risk to South Australia from a further generation of locusts remains very low compared with 2010 and early 2011. Emerging populations are highly localised in the Mid North, in very small patches; fly-ins from other regions or States are not expected.

The Locust Hotline received only sporadic reports of locust activity during December, mainly in the Mid North region. (Last month high density adults and a few swarms were identified in the Peterborough–Burra–Spalding–Jamestown area). Locust numbers are small and any reports of swarming appear to be small, localised and becoming dispersed.

Recent wet weather may be conducive for adult locusts that are ready for egg laying. Locusts like laying eggs in wet soil and recent rain my help synchronise the timing of laying. If locust nymphs hatch later this month, there could be the possibility of some small, localised locust bands later in February. However, this will depend upon the extent of the current adult population and how conducive conditions are for the remainder of January.

There is usually high nymph mortality (often averaging 30% in the first instar stage of development, up to 88% in total over all instars) however, this could be lower if conditions are good and the nymphs are subjected to low levels of attacks by parasites that feed on juveniles.

The recent Australian Plague Locust Commission forecast indicates that there is negligible likelihood of locust fly-ins from interstate over summer/autumn.  Biosecurity SA and the APLC will continue to undertake surveys of usual locust habitats.

The Locust Hotline continues to receive low numbers of reports of locusts – mainly adults – but in irregular distribution and in small numbers.

Adult locusts can be expected to be seen during the remainder of December in those areas where hoppers were reported earlier in the season however numbers will not be of the extent of last summer. Landholders who are able to spray any ground-based hoppers that may remain are encouraged to do so, but also pay regard to any withholding periods that may apply for crops not yet harvested.

Reports of locust sightings continue to be received by the Locust Hotline but reports are very low in number. One report recently received was of adult locusts flying in the Burra region.

Between now and later in December, adult locusts can be expected to be seen in areas where hoppers have previously been reported. However, numbers and their extent will be much reduced when compared to last year. Some nuisance swarms can be expected with the potential to move across agricultural districts in coming weeks.

• Patches of locusts are continuing to be reported, primarily in the Mid North region and Murray Flats. Very few new reports are being received from other regions.
• The affected area in the Mid North, which now extends from Peterborough to Eudunda, is the most significant area of locust activity with more than 30 reports received from this area.
• Locusts are starting to fledge in the southern Flinders Ranges, Mid North, Murray Flats and western Eyre Peninsula districts. Remaining nymphs are mainly fourth and fifth instars although some areas also have numerous younger nymphs at second and third instars indicating later hatchings.
• Producers should continue to undertake control of locust hopper bands wherever possible taking particular care to adhere to any chemical withholding periods that may apply for both crop harvest and livestock grazing.
• Locust populations and distribution continues not to meet Biosecurity SA aerial control criteria.
• Adult locust will be observed flying around through the remainder of November and into December as more nymphs fledge.
• Nuisance swarms are also likely to start developing in the above mentioned areas with the potential to move across agricultural districts in coming weeks.