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About the Locust Bulletin
About the Locust Bulletin
Locust population densities
Density classes for nymphs and adults
Bands
Swarms
Locust control
Other terms mentioned in the Locust Bulletin
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About the Locust Bulletin
The Australian Plague Locust Commission (APLC) produces a monthly Locust Bulletin during times of locust activity (approximately September to May). The Bulletin reports the current and previous month's locust situation and weather events of potential significance to locust developments. The Bulletin also gives a forecast of likely developments in the following six weeks for Australian plague locust Chortoicetes terminifera, spur-throated locust Austracris guttulosa, and the migratory locust Locusta migratoria (see our About Locusts page for details on the biology and distribution of each species)
The terms used in the Bulletin to describe the biology behaviour and population density have defined meanings to ensure accuracy and usefulness. To be of value, forecasts and risks also use defined terms and these are detailed on this page and the glossary of terms. The forecasts are dependent on current locust population distribution information, and weather and environmental conditions. Risk statements use both the probability and the potential consequences of an occurrence.
The majority of information documented in the Bulletin comes from regular surveys by the APLC. Additional information comes from landholders, Departments of Primary Industries in New South Wales, Queensland, NSW Rural Lands Protection Boards (RLPBs), Primary Industry and Resources South Australia and from the public.
During major locust control campaigns involving the APLC, a brief weekly summary of control activities is issued, titled Locust Management Advice. This document summarises insecticide usage, areas affected and likely future developments and is circulated to a range of stakeholders including state agriculture authorities and various industry bodies. Current information on control activities can also be obtained by telephone from APLC Headquarters on 1800 635 962. An answering machine is attached for after hours calls.
Locust population densities
A characteristic of locusts is gregarious behaviour and the formation of high density population units known as bands of nymphs and swarms of adults. Where higher densities occur, a large proportion of the regional population is concentrated in small areas occupied by these units, with lower densities elsewhere, so the high densities cannot be extrapolated to the area of an entire region. Typically a range of density classes is found within surveyed regions with higher densities where habitat conditions are favourable. Where common terms are used for specific density classes, the word is capitalised (Scattered or Concentration), while more general density classes (such as low or high) apply to a broader range of specific density classes.
The following terms are used to describe different density levels
Density classes for nymphs and adults
|
Nymph Densities |
Number per m2 |
|
|---|---|---|
|
Present (P) |
1 - 5 |
|
|
Numerous (Num) |
6 - 30 |
|
|
Sub-band (SB) |
31 - 80 |
|
|
Band (B) |
> 80 |
|
|
|
|
|
|
Adult Densities |
Number per m2 |
Number per hectare |
|
Isolated (Iso) |
- 0.02 |
< 200 |
|
Scattered (Scat) |
0.03 - 0.1 |
>200 - 1000 |
|
Numerous (Num) |
0.2 - 0.5 |
>1000 - 5000 |
|
Concentration (Conc) |
0.6 - 3.0 |
>5000 - 30,000 |
|
Low Density Swarm (LDS) |
4.0 - 10 |
>30,000 - 100,000 |
|
Medium Density Swarm (MDS) |
11 - 50 |
>100,000 - 500,000 |
|
High Density Swarm (HDS) |
> 50 |
>500,000 |
General regional density classes
|
Regional Nymphal density |
Survey densities |
|---|---|
|
very low, occasional |
Nil-Present |
|
low |
Present-Numerous |
|
medium |
Numerous-Subband |
|
high |
Bands |
|
|
|
|
Regional Adult Density |
Survey densities |
|
very low, occasional |
Nil-Isolated |
|
low |
Isolated-Scattered |
|
medium |
Scattered-Numerous |
|
high |
Concentration-Swarm |
Bands
Three parameters are used to define bands of locust nymphs:
- The size of a band as indicated by the length of the band front.
- The infestation level which is measured by the length of band front per square kilometre in a limited area of about 5 km2 (most often a paddock).
- The number of bands in a specified area (eg. the Hillston-Hay area).
Term Band length (m) Term km band front/km2 Term No. of bands
Band SizeInfestation level Number of bands in a specified area very small <10 Light 0 - 0.5 One ot two
1 - 2 small 10 - 100 Medium 0.6 - 2 A few 3 - 10 medium 101 - 1000 Heavy >2 A number 11 - 50 large 1001 - 5000 Many, a large number >50 very large > 5000
Swarms
The size and number of swarms in a specified area are referred to when detailing an infestation.
Term Swarm area (km2) Term Number Swarm Size Number of swarms very small <1 few, some 3 - 5 small 1 - 2 a number 6 - 10 medium 3 - 10 many 11 - 50 large 11 - 20 very many, a large number, numerous >50 very large >20
Locust control
The APLC only undertakes aerial control of locust nymphs and adults. Nymphal band control will only be initiated by the APLC if targets are large and dense enough to be visible from the air. A minimum of 10 km2 of targets is required for control to be economically feasible for adults and nymphs.
Other terms mentioned in theLocust Bulletin
Terms used in the Bulletin to refer to rainfall and forecast probabilities (ie the likelihood that an event will occur). These are defined below.
Term Rain falling in one week (mm) Rainfall Light 0 - 15 Moderate 16 - 35 Heavy 36 - 100 Flood >100
Forecast probabilities
Term Chance that event will occur (%) Unlikely, low risk <30 May, moderate 30-70 Likely, high risk >70
For a definition of more terms used in the Locust Bulletin see the Glossary.
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If you would like to be on the mailing list to receive hard copies of Locust Bulletins, please send your name and postal address to us by email or alternatively, provide them by post to the:
Forecasting & Information Officer
Australian Plague Locust Commission
Australian Government
Department of Agriculture, Fisheries & Forestry
GPO Box 858
Canberra ACT 2601