By allowing ads to appear on this site, you support the local businesses who, in turn, support great journalism.
Low Mosquitofish Numbers Create District Challenges

Two current challenges facing San Joaquin County Mosquito and Vector Control District are low mosquitofish production and the proliferation of the Western treehole mosquito.

“Although these challenges are occurring, the District wants the public to know they are temporary,” said Aaron Devencenzi, District Public Information Officer.

In the meantime, Devencenzi added, the District has some information to share with residents.

Due to a cold winter and cool weather extending into spring, mosquitofish (Gambusia affinis) development was hindered, making less fish available for the public. The low availability is also evident in known wild sources.

“As the weather warms soon, we expect to see an increase in the mosquitofish production,” said Devencenzi. “Until mosquitofish are readily available, we will be prioritizing their use. We continue to encourage the public to request mosquitofish. Upon requesting fish, we will inspect and if necessary, treat the source.”

The location address will be included on a list for future mosquitofish delivery. District officials also encourage homeowners with neglected swimming pools to consider cleaning and restoring the water to swimmable conditions. Other sources of water will be handled on a case-by-case basis after inspection. There is no direct cost to request service, as the Mosquito and Vector Control District is funded through public tax dollars.

The second situation is the emergence of the Western treehole mosquito.

“Normally, this species is one of the first to emerge as the weather warms in the spring. We have been fortunate in the past few years that this species has been less of a nuisance due to several drought years,” said John Fritz, District Assistant Manager.

As the name implies, this species develops in treeholes, holes in the trunk of trees and even in artificial containers and tires.

Fritz added, “Because of the wet winter, dormant eggs are hatching in large numbers.”

The District will continue monitoring the situation but wants to remind the public that this is only a temporary occurrence.

Also, officials continue to stress that mosquitoes only need a tablespoon of water to develop. Residents are asked to look around their property and remove even the smallest amounts of water. It is also essential to remove any unwanted containers and store necessary containers in a dry area.

Last, use insect repellent containing EPA-registered active ingredients, including DEET, Picaridin, oil of lemon eucalyptus, or IR3535, according to label instructions, when outdoors. Wear long pants, loose-fitting long-sleeved shirts, and other protective clothing outdoors. Be sure that your home has tight-fitting screens on doors and windows.

Ground and aerial spraying has already occurred in several areas of the county – including ground spraying in the Escalon region – as the District looks to control the mosquito population in hopes of preventing outbreaks of West Nile Virus. The latest ground spraying in Escalon was scheduled for Tuesday morning, May 2 in the rural southeast Escalon area, near Lemon, the SSJID canal, east to Sutliff, west to Santa Fe and Harrold.

To learn more about San Joaquin County mosquito and vector control activities, visit the District’s website at Follow them on Facebook @SJmosquitoandvector for more tips and information. To request District service, call 209-982-4675, 1-800-300-4675, or visit