Mosquito numbers across Grand Cayman are beginning to decline after reaching high levels earlier this month, according to the Mosquito Research and Control Unit (MRCU).

The latest trap data show a drop in mosquito activity, with collections falling from 9,309 mosquitoes on June 18 to 4,723 on June 22. While numbers remain higher than normal, the MRCU said the downward trend is a positive sign.

However, Cayman Islands officials warned that weather conditions continue to make mosquito control operations challenging, particularly aerial spraying efforts.

The most effective time to target adult mosquitoes is a short window beginning about 15 minutes after sunset and lasting roughly three hours. If rain, lightning or unsafe flying conditions occur during that period, aircraft operations must be cancelled.

Aerial spraying is carried out across different operational zones, including West Bay, George Town, North Side, East End, South Sound, Bodden Town, Newlands, Prospect and surrounding communities. The MRCU said areas are prioritised based on mosquito trap data, field inspections, weather conditions and reports from residents.

Ground operations using truck foggers are also continuing, but these cover a smaller area and are also affected by rainfall.

Despite the recent decline, the MRCU said further increases in mosquito numbers are possible following rainfall. Officials noted that mosquito populations often rise about 10 days after heavy rain, depending on standing water and breeding conditions.

The unit said mosquito control involves more than spraying, with teams also carrying out breeding site inspections, larviciding, trap monitoring, data analysis and responding to public reports.

Residents are being encouraged to help reduce mosquito breeding by removing standing water around homes, covering water containers, clearing gutters and reporting areas with high mosquito activity.

The MRCU thanked residents for their patience as efforts continue to reduce mosquito populations across the island.