Locusts kept under control

15 Dec, 2004 10:00 PM
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WHAT could have been a moderately severe Australian Plague Locust outbreak has been successfully nipped in the bud by an Agriculture Department aerial chemical control program completed this month.

Predictions of a moderate to severe outbreak in spring this year had resulted in Cabinet approving an extra $500,000 to fund contract spraying of up to 50,000ha in both the state¹s north and south agricultural areas if necessary.

But Agriculture Department acting incident coordinator Dennis Rafferty said only 30,000ha were sprayed, the majority in the southern part of the state.

The controls cost less because in some areas where the locusts first hatched, there were high mortality rates due to cold weather.

³We haven¹t done an assessment yet on the total cost, but because the level of control necessary was at the lower end of the scale, some of the funds will be returned to the government,² Mr Rafferty said.

³The objective of the department¹s program was to prevent the formation of large swarms, which we think at this stage we have been successful in achieving.

³That is not to say that there won¹t be minor swarms, because we can¹t spray every locust in the state.

³We are asking landholders to keep an eye on locusts that are landing and appear to be laying eggs. If we know where the egg beds are, we know where to spray."

Agriculture Protection Board regional operational manager for locusts, Ron Payne, said spraying began on November 2.

The program was much smaller than that undertaken in 2000-2001.

³It¹s over a similar area but a bit further north this time,² Mr Payne said.

³I think we sprayed about 60,000ha in 2000 and this time it will end up close to 30,000ha, so it is about half as much as last time."

Mr Payne said farmers had brought locust hatchings to the department¹s attention and some had conducted their own spraying programs to help keep them under control.

³A lot of the farmers have done work themselves on banding where they found it earlier on. We then come in with planes and our staff surveys all the pasture paddocks in those areas and then we work out the numbers of locusts coming off those paddocks," he said.

"Then we can work out what we call a priority target zone, which is where it¹s likely to develop into a big swarm where you get millions of locusts coming off that area.²

Mr Payne said locusts posed the most serious threat when they were able to fly, landing en masse and feeding voraciously on green material to build up body fat to become fertile and begin laying eggs.

Spraying was conducted at the insects' third or fourth growth stage (the instar), prior to the locusts reaching adult status at about the fifth instar.

While spraying had been effective, rural residents could still expect to see some adult locusts.

Swift action was the key

A POTENTIAL locust outbreak this year was swiftly brought under control by a combination of environmental factors and control methods implemented by locust control specialists.

However had the response from the Agriculture Department and Agriculture Protection Board not been as swift, the damage may have been greater and the control expenses much higher.

Plague locust control team senior entomologist Kevin Walden said prediction models had indicated that if climatic conditions had remained ideal over September-October 2004, spraying may have been necessary over 50,000ha.

Ideal locust hatching conditions would have been created if it had rained prior to hatching and the weather had remained warm rather than hot.

³(The outbreak) is definitely at the lower end of the range due to those factors,² Mr Walden said.

Department staff and others helping to control locust outbreaks had learned much since the first major campaigns were launched more than 10 years ago.

³This is the fifth major locust outbreak campaign that the department has launched since 1990,² Mr Walden said.

³Computers play a major part in simulation models, which is vital to the work of people in the field.

³Some of that (progress) is due to technology, but just as much, if not more, is due to staff gaining experience in the field and relating it back to us."

Mr Walden said regional debriefings which took place last week allowed staff in the field to relate their findings to staff in the office, resulting in better methods and understanding all round.

³We have got some staff who are quite innovative ‹ for example in the Esperance area, we have guys who are working on different methods of recording information,² he said.

The Esperance team had set up a system enabling locust activity monitoring from a remote location.

³So, if in the future we have a big outbreak, and we have to have a series of bases, this information will help,² Mr Walden said.

And the problem may well crop up again in the future.

³The locusts won¹t just go away. They are a native species and they will always be there and we just have to learn to control them. We are getting better at that, more efficient,² he said.

Mr Walden said flexibility and the speed of communicating information was vital to the department¹s response to locust outbreaks. Response could not be rapid without grower co-operation.

³We have to thank the farmers who work with us,² Mr Walden said. ³We simply can¹t get the job done without them.

³From the beginning of September we had phone calls letting us know about hatchings, which allowed us to concentrate on infestations early on.²

FARMERS have a responsibility to help prevent a widespread future outbreak of Australian Plague Locusts by keeping an eye out for hatchings on their properties.

While the Department of Agriculture and the Agriculture Protection Board play a vital role in halting the spread of locust swarms, individual landholders are responsible for controlling immature locusts on their own properties.

Emerging nymphs and swarming locusts can cause severe damage to crops and pastures, intensive horticultural enterprises, sporting grounds, orchards, vineyards and domestic gardens.

The native insect commonly exists in low numbers in Western Australia¹s pastoral regions and numbers will increase when the weather is warm and damp.

Department of Agriculture bulletins describe locusts as ranging in length from 24-40mm and from dark to light green or brown. Most are dark brown although some are bright green in winter. To identify adult locusts, look for dark blotches on the outer edge of hind wing, and red colouration on the inside of the hind legs.

Several generations locusts are born in a year, with adult locusts laying egg beds, usually in hard, bare ground. Incubation depends on temperature and moisture, as does fertility.

Locust swarms can move several kilometres a day, or in less frequent night migrations, more than 100km in an evening.

The Australian Plague locust should not be confused with the wingless grasshopper (Phaulacridium vittatum), which often occurs in coastal cropping regions, according to the department¹s bulletin.

While both can cause damage to crops and pasture, the wingless variety are not able to travel large distances and farmers need to control this pest themselves.

For more information on the plague locust and control methods such as spraying, ploughing and natural control methods, visit the department¹s website, www.agric.wa.gov.au and follow the links to bulletin 4638.

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