Understanding Professional Mosquito Traps

Mosquitoes are like any other pest: Integrated Pest Management (IPM) is always the best option. We do have many magical wands we can choose from when it comes to dealing with them. Sanitation is always the first line of defense, but we know we can never eliminate every water source in an area. It’s fairly easy to keep them out of structures and treatments are a valuable “potion.” Traps are another good addition to our spell book.

THEY AREN’T NEW. One of the earliest mosquito trap mentions is in a book from 1902 titled “Mosquito Brigades and How to Organize Them,” by a British naturalist1. Traps utilizing light were first developed in New Jersey in 19272. Starting in the 1970s, new traps that focused on mosquito eggs (gravid traps), carbon dioxide traps and sentinel traps were deployed. Much of this was done by scientists looking to trap, monitor and research mosquitoes. It wasn’t until fairly recently that we started using mosquito traps as management and control devices.

Fun fact. The first bug “zapper” was featured in “Popular Mechanics” in 19113. The first patent was granted in 1934.

Traps now range from small table-top models to larger, almost refrigerator-sized boxes. They use various means of attracting adults to either kill them or entice them to lay their eggs. Once they lay their eggs, the traps control the immature stages. Water, scents, light, colors and gases are used alone or in some combination. Since these are all cues females use to find their hosts and oviposition sites, it makes sense to use them in a trap.

Fun fact. The odds of capturing mosquitoes were 292% higher for CO2-baited traps than for those baited with scents.4

THEY WORK. Numerous studies have shown that traps lure in mosquitoes and mosquitoes will deposit their eggs. Mosquito traps are designed for container- breeding species like Aedes and Culex. If those aren’t the species you are trying to battle, traps won’t be helpful. The question becomes: Does a trap have a significant impact on mosquito populations and is it economically effective?

Research projects on numerous types of traps have investigated traps on a larger, community-wide scale. We know mosquitoes don’t respect fence lines or map borders. Using a single mosquito trap on acres of ground isn’t going to reduce the population. On a large scale, when traps were deployed throughout a neighborhood or large area, residents saw a reduction in mosquitoes. On a smaller scale, say a backyard, multiple traps are still typically needed. Most commercially available traps typically recommend two or more traps in a typical residential setting.

Fun fact. While many species of mosquito don’t travel too far (one mile), salt marsh mosquitoes have been known to fly 40 miles!5

PLACEMENT IS KEY. Trap efficacy also is determined by how they are placed. Like baiting for cockroaches, if you don’t get the bait in the right spot, it won’t work. Think of where adult mosquitoes hang out. They typically like shaded, cooler areas with vegetation for them to rest on.

Areas near water sources also are a draw so traps need to be placed in those areas. It can be hard to find a suitable area that is flat enough so the trap won’t tip over or a lawn mower won’t destroy it. While these traps aren’t necessarily harmful to people, we don’t want them easily accessible by people, pets or non-targets. There will be some areas that just aren’t suitable to place a trap. Like placing any pest control device, the situation should be constantly reevaluated. Changes will happen and stations need to be reassessed.

Many mosquito traps incorporate or suggest adding some type of pesticide. It may be an adulticide to knock down the females and take them out of the equation, or it could be larvicides to impact the immature stages. It may be a combination of the two. Choosing the right product is important. Some products may not be registered in all states. Some formulations may last longer than others. Because there is a relatively small amount of water in the traps, it may not be possible to use a small enough quantity of pesticide. Most larvicides work great in these. There are numerous actives to choose from, like Bacillus thuringiensis, Beauveria bassiana, spinosads and insect growth regulators. These are usually in some kind of solid form, such as pellets, which makes them easy to add to the water receptacle.

Fun fact. Spinosad was discovered in soil samples from an old rum mill. This proves that rum really does fix everything!

COMBO TREATMENTS. Another consideration is using traps in conjunction with sprays or fogs. While some of these mosquito traps have some type of adulticide, they primarily work on the immature stages. That means a lot of adults are still out flying, biting and reproducing. Knocking the adult stage down is a great idea in conjunction with other IPM tools like traps. Since traps should be placed in shaded, vegetated areas and sprays/fogs should be directed higher at where resting adults are found, there won’t be too much overlap when you look at two treatment areas.

Fun fact. Wood submerged in water was more effective, collecting almost double the number of eggs than with a non-scented blank.6

The key is not to contaminate the water inside the trap with another product. The traps should be placed before making any liquid applications. Some adulticide contacting the outside of the trap isn’t necessarily negative. Adults resting on the outside of the container can pick up some of the treatment and be knocked down. It’s also a safety issue. You don’t want to apply a liquid, then have to go back into that treated area to place the traps.

Fun fact. Artificial light at night, in conjunction with higher temperature, is significantly associated with the number of larvae of Ae. aegypti hatched from eggs collected in ovitraps.7

OTHER CONSIDERATIONS. Costs will factor into your trap of choice. Much like rodent bait stations, adding a station incurs the cost of the station and materials and the cost to service it. Many residential properties are serviced quarterly, or every two months. When using mosquito traps, there may be an increase in visits, which adds to the customer’s cost. Different types of mosquito traps have different base costs. Time to service those also varies.

Weather can be a factor in trap efficacy. Even with traps placed in shaded areas, extreme heat can evaporate all the water out of the station. An extreme rain event could flood the stations, removing the larvicides. Heavy wind, animals and lawn care could tip over the stations. Like anything, mosquito traps are not a stand-alone tool.

A good spell includes many ingredients, and when it comes to mosquitoes, traps can be part of that. Like any pest situation, multiple tools can be used to increase the odds of a better reduction. As with any pest control tool, nothing will ever be completely effective. Different situations will call for different tools. That’s the magic of pest control!

The author is the consulting entomologist at 360 Pest and Food Safety Consulting.

References

1 https://www.ajtmh.org/view/journals/tpmd/s1-11/2/article-p147.xml

2 https://vectorbio.rutgers.edu/outreach/njtrap.htm

3 https://home.howstuffworks.com/bug-zapper.htm#:~:text=Inside%20a%20Bug%20Zapper,of%20the%20bug%20zapper%20are:

4 https://link.springer.com/article/10.1007/s00436-024-08224-y

5https://www.mosquito.org/faqs/#:~:text=Depending%20upon%20the%20species%2C%20mosquitoes%20can%20fly,species%20have%20flight%20ranges%20of%201%2D3%20miles.

6 https://sciforum.net/paper/view/22722

7 https://www.sciencedirect.com/science/article/abs/pii/S0048969725023320