During the warmer months of the year, we conduct mosquito larvae monitoring at the Seaford Wetlands and coordinate management actions to control outbreaks.
We’re responsible for managing Seaford Wetlands in our role as caretaker of rivers, creeks and wetlands across the Greater Melbourne region. The wetlands naturally attract large numbers of mosquitos, but are not the only source of mosquitos in the area.
Why this is important
Melbourne is currently free of dengue fever, chikungunya and yellow fever. This would not be possible without the work of the Department of Health, Department of Energy, Environment and Climate Action, and Melbourne Water.
Monitoring is regularly conducted to make sure vector carriers like the African Yellow Fever mosquito (Aedes aegypti) that are present in most tropical/subtropical countries of the world do not end up in Melbourne.
What’s happening and when
We monitor the wetlands monthly starting around August each year, and continuing during the warmer months until the seasonal conditions no longer favour mosquito development. Rain patterns make habitat more available, with extra water inundating areas that haven’t been wet in a few years.
Our activities include:
- monitoring adult mosquitos and larvae
- sending adult mosquitos to labs run by the Department of Energy, Environment and Climate Action for identification and examination for arboviruses
- inspections to assess the effect of rain on mosquito larvae numbers
- treatment and control of mosquito larvae if outbreak numbers are found.
If larvae numbers are excessive, larvacite briquettes are distributed in the wetlands. The briquettes mimic the juvenile mosquito hormone and disrupt the development of larvae and pupae in the water, with minimal impact on other fauna. They act for up to 150 days.
Latest monitoring results
| Month |
Resulting actions |
|---|---|
| Late November 2024 | Since the previous survey in October, water levels have fallen slightly. Low abundances of adult mosquitoes were recorded at all three traps, with a total of 59 female specimens collected. Based on the November 2024 monitoring results, no treatment has been recommended for this month.. |
| September 2024 |
Since the previous survey event in August, rainfall has increased, and water levels have risen. Numerous small pools and puddles are visible across the wetland, which may provide habitat for larvae. Based on the September 2024 monitoring results, no treatment has been recommended for this month. The next round of mosquito larvae and adult monitoring will occur in late-October. |
| August 2024 |
The August monitoring event has been carried out in accordance with the Melbourne Water Mosquito Management Plan. This monitoring event allowed for a survey across the entire Seaford Wetlands. The survey focused on areas where mosquito ‘hot spots’ have been detected in the past and on areas close to houses. |
| April 2024 |
Very low numbers of adults at all three of the trapping locations which isn't unusual at this time of year as we're moving into the colder months. During the larval survey we found that water levels have increased across the wetland following the rain we've seen throughout the month, and as expected, this has seen an increase in larval numbers in several locations which will require treatment. |
| February 2024 |
Since the previous survey in January, water levels across the wetland have dropped. There were low abundances of adult mosquitoes at all three sites. A total of 14 locations were surveyed for mosquito larvae around the wetland. There were no mosquito larvae found at any of the locations, and six of these locations around the margins of the wetland were dry. |
| January 2024 |
We only completed adult trapping at this visit and noted the abundance of adults to be high at 2 of the 3 sites. Since the previous survey in December, water levels across the wetland have dropped. However, occasional high rainfall has maintained some pools on the margins of the wetland, which can provide habitat for mosquito larvae. No treatment recommended. |
| December 2023 |
Adult abundances have remained low. Two locations were highlighted for larval treatment, both were in fairly small shallow pools. Given recent rainfall there are still numerous small shallow puddles amongst vegetation around the periphery of the wetland. There are likely similar puddles outside the boundaries of the wetland as well and these could also potentially be contributing to mosquito numbers around the area. |
| September 2023 |
The first sampling event for the 2023-24 season. Adults and larvae numbers were both fairly low. Treatment was recommended and undertaken at 7 locations. |
| October 2023 | Warmer weather and a lack of rain has caused water levels to drop throughout the wetland. Several monitoring sites were dry, especially on the edges of the wetland. However, high numbers of larvae were identified in pools in the central and southern sections. Treatment was recommended at six locations. |
| November 2023 | This visit was for adult trapping only. There were low abundances of adult mosquitoes across the traps. No treatment was recommended. Numerous shallow pools amongst vegetation were observed, having been formed by rainfall in the days prior to the survey. Should these pools persist through December they will be targeted during the next larval survey. |
Previous monitoring results
- 2022-23 season
-
Month Resulting actions
April 2023 Adult numbers were found to be quite low at the three trapping sites. Larvae were found at a couple of locations and two treatment areas were recommended. March 2023 March was scheduled to be a survey of adults only. However, in response to the high adult numbers in recorded in February some additional targeted survey for larvae was undertaken in the area around the old bird hide. No larvae or pupae were recorded at any of the locations checked in the targeted search and there were no treatment recommendations.
Adult numbers were considerably lower than last month.February 2023 Mosquito larvae and pupae were not found at any of the 25 locations surveyed across the wetland, and seven of the sites sampled were found to be dry.
Low to high numbers of adults were found this month. High numbers of species which breed preferentially in shallow fresh waters amongst vegetation were found. These types of small, transient puddles may be disconnected from previously treated areas so would not have received benefits from treatments deployed in prior months. Treatment was not recommended as treatment only controls larvae not adults; however, additional targeted larvae survey will be scheduled for next month.January 2023 Low numbers of adults were recorded, and no treatment was recommended. The low numbers of adults recorded also indicates the treatment deployed across the wetland has helped reduce adult emergence. High numbers of Ceratopogonidae, commonly known as ‘biting midges’ were also detected at Seaford North Primary School. While Ceratopogonidae can be a nuisance, they are not considered a risk for disease in humans. December 2022 Mosquito larvae and pupae were found at 7 of the 29 locations surveyed across the wetland and were particularly abundant throughout areas adjacent to, or very nearby, the track that runs through the centre of the wetland. Larval abundances ranged from high to extreme. Low to high numbers of adults were found this month, with a total of 392 female mosquitoes collected across the three traps. This is a considerable decrease compared with the November monitoring. The adult mosquito diversity suggests that larvae are maturing in recently formed rain puddles. 5 areas requiring treatment were identified. November 2022 Mosquito larvae and pupae were found at 11 of the 13 locations surveyed. Larval abundances ranged from high to extreme. High to very high numbers of adults were found this month, with a total of 3,050 female mosquitoes collected across the three traps. This is a substantial increase compared with October monitoring, where only 46 adult females were collected.
The significant rise in numbers in November is likely caused by the weather with individuals maturing in the numerous shallow puddles around the wetland. Higher temperatures have also likely contributed to in the increase in adult mosquitoes. Several large sites located to the east of the wetland were identified as needing treatment.
October 2022 Treatment was recommended and undertaken at 6 locations. Recent heavy rainfall caused water levels in the wetland to rise considerably. This has provided additional habitat for mosquito larvae, especially in the pools on the margins of the wetlands. Late September 2022 Low numbers of adults were recorded. The wetland received targeted treatment following the intensive survey in early September. The low numbers of adults recorded suggests that the treatment deployed across the wetland has helped limit adult emergence. Early September 2022 The first sampling event for the 2022-23 season. Treatment was recommended and undertaken at 12 locations. - 2021-22 season
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Month Resulting actions March 2022 Surveying consisted only of adult trapping this month, and demonstrated that the numbers of adult mosquitos are continuing to stay quite low across all traps. The number of adult mosquitoes has increased marginally from February but is still greatly reduced compared to monitoring events early in the 2021/22 season. This suggests that the treatment deployed across the wetland, combined with widespread drying of pools over summer, has helped reduce adult emergence. February 2022 Mosquito larvae and pupae were found at none of the 21 locations surveyed across the wetland. Nine of the locations visited were dry. Adult female mosquito abundance in each trap collected for February were low, and no treatment was recommended. January 2022 The number of adult mosquitoes had reduced substantially compared to all previous monitoring events for the 2020/21 season, likely as a result of the treatment in December combined with falling water levels across the wetland over the previous weeks. December 2021 One adult trap had been tampered with, thus results in that location had to be partly assumed. Larval abundance was moderate to high. Briquette treatment was carried out in identified areas November 2021 Adult abundance in each trap was moderate to high. Larvae sampling was not scheduled to be undertaken. October 2021 Mosquito larvae and pupae were found at three of the fifteen locations surveyed across the wetland with larval abundances ranged from low to moderate. Adult abundances ranged from low to moderate. Briquette treatment was carried out in identified areas. September 2021 Mosquito larvae and pupae were found at 34 of the 51 locations surveyed across the wetland, with larval abundances ranging from low to extreme. Adults abundances ranged from low to high. Treatment was recommended at eleven locations this month and briquette treatment was - 2020-21 season
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Month Resulting actions
April 2021 Larval sampling and adult-trapping were completed. Low numbers of adults and larvae were found. No treatment was recommended. March 2021 Unscheduled, larval survey was undertaken across the northern “eel race” section of the wetland to assess the availability of larval habitat, very high numbers of larvae were found in this area. Low abundance of adults. Briquette treatment was carried out in the identified areas of high larval numbers. February 2021 Larvae was not detected at any of the sampled locations. Adult abundance was very low. Treatment was not recommended for any site. January 2021 Adult abundance was low. Larval sampling was not undertaken. Treatment was not recommended for any site. December 2020 Both adult and larval abundance were low to moderate. Briquette treatment was carried out in identified areas. November 2020 Adult abundance was low. Larval sampling was not undertaken. Treatment was not recommended for any site.
October 2020 High to very high larvae abundances was found and briquette treatment was carried out in identified areas. Adult numbers were low-high. September 2020 Low to extreme larvae abundance was found and briquette treatment was carried out in the identified areas to stop larvae forming. Adult numbers were found to be low to high. - 2019-20 season
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Month Resulting actions
April 2020 (final monitoring for the season) One site out of nine was reported to have larval populations with this population deemed to be extreme. Water levels were high due to 76mm of rain falling in the week prior to sampling. Adult numbers were moderate to high with female numbers remaining constant. March 2020 A high number of adults were found in this survey, with larvae and pupae being abundant in 11 of the 24 sampling sites. February 2020 Low to extreme numbers of larvae were found in the wetlands. Briquette treatment was applied to the areas identified to stop larvae developing into adults. Adult numbers were low-high. December 2019
Low to extreme numbers of larvae were found in the wetlands. Briquette treatment was applied to the areas identified to stop larvae developing into adults. Adult numbers were low-moderate.
Please note that high numbers of biting midges were found particular at the Seaford North Primary School. Unfortunately there is no known efficient methods of controlling them.
October 2019 Very high and extreme numbers of larvae were found in the wetlands. Briquette treatment was applied to the areas identified to stop larvae developing into adults. Adult numbers were low. September 2019 Moderate to high numbers of adults were found but low number of larvae in the wetland. Larvae monitoring will be carried out next month. No additional treatment is recommended at this time.
- 2018-19 season
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Month Resulting actions
March 2019 Low numbers of larvae were found in areas of the wetlands. Briquette treatment was applied to the areas identified to stop larvae developing into adults. Adult numbers were lower than in the previous month. January 2019 Very high-high numbers of larvae were found in areas of the wetlands. Briquette treatment was applied to the areas identified to stop larvae developing into adults. Adult numbers were lower than in the previous month
November 2018 High numbers of larvae were found in areas of the wetlands. Briquette treatment was applied to the areas identified to stop larvae developing into adults. Adult numbers were low-moderate.
September 2018 Very high numbers of larvae were found in areas of the wetlands. Briquette treatment was applied to the areas identified to stop larvae developing into adults. Adult numbers were low.
August 2018 High numbers of larvae were found in areas of the wetlands. Briquette treatment was applied to the areas identified to stop larvae developing into adults. Adult numbers were low.
What you can do at home
You can protect yourself from mosquitos by:
- getting rid of stagnant water around the home or campsites, where mosquitos breed, including:
- old tyres
- unused fish ponds
- unsealed water tanks
- pot plant holders
- ensuring that insect screens fitted to doors and windows are in good condition
- wearing long, loose-fitting clothing and using a suitable insect repellent (containing picaridin or DEET as an active ingredient) on exposed skin during the warmer months of the year.
For further information and advice, visit the Victorian Government’s Better health - beat the bite webpage.
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