Mosquito Control in Delaware

Delaware has two mosquito species of primary public health concern. The Asian tiger mosquito (Aedes albopictus) is the most common day-biting species in residential yards and is the one most people encounter during outdoor activities. It is a competent vector for La Crosse encephalitis and has the potential to transmit dengue, Zika, and chikungunya if those viruses are introduced. The northern house mosquito (Culex pipiens) is the primary nighttime biter and the most significant vector for West Nile virus in Delaware, which the Delaware Division of Public Health monitors with annual surveillance. Eastern equine encephalitis (EEE), while rare, is present in the mid-Atlantic region and transmitted by Culiseta melanura in wooded wetland areas. 

Practical implication: Because Asian tiger mosquitoes breed in very small containers (bottle caps, clogged gutters, low spots in tarps), reducing standing water on your property directly reduces the species most likely to bite you in your yard. Professional barrier treatments are most effective when combined with standing water elimination, because no treatment can compensate for active breeding sites that produce new adults every 7-10 days.

Professional barrier treatments applied every 21 days are calibrated to that interval because mosquito adults can repopulate treated areas within 2-3 weeks from new breeding sources. Between visits, the most impactful actions are eliminating standing water in any container holding water for more than 7 days: gutters, bird baths, saucers under planters, tarps, children's toys, and low areas in lawn edging. Treating ornamental water features with Bti (Bacillus thuringiensis israelensis) dunks available at hardware stores kills larvae without harming fish, frogs, or other wildlife. Cutting grass regularly and trimming dense shrubs reduces daytime resting habitat for Asian tiger mosquitoes, which shelter in dense vegetation during the heat of the day. Dense vegetation near the home's perimeter, particularly in shaded areas, is where professional barrier treatments are most critical because these are the areas where adult mosquitoes aggregate before entering living spaces.

This is one of the most common and legitimate concerns with mosquito programs. Products used in professional barrier treatments (typically bifenthrin- or permethrin-based formulations) are toxic to bees and other beneficial insects during wet application and for a short period afterward. The risk to pollinators is reduced by applying treatments in the early morning or evening, when bees are least active and plants are not in bloom, targeting the undersides of leaves and the interiors of shrubs, where mosquitoes rest, rather than flower surfaces. Flowering plants should not be directly treated. Some companies offer essential-oil-based barrier treatments (cedarwood, rosemary, and lemongrass active ingredients) as an alternative for properties with heavy pollinator activity or certified organic gardens. These provide a shorter residual window (7-10 days versus 21 days) but carry a lower risk profile for beneficial insects. 

If you have an active garden with pollinators, discussing treatment timing and product selection with your technician before the first visit helps structure the program to your specific landscape.