By Nicky Gallagher, Ph.D., technical services manager, Professional Pest Management, Syngenta
The Asian tiger mosquito, Aedes albopictus, is an aggressive human biter and is often the mosquito species that elicits the most complaints in areas where it resides. This mosquito is a daytime biter and can drive people indoors. It likes to be around humans and our habitats, preferring dark, humid resting sites. In backyard environments, it can be found on the underside of leaves and other shady areas. It will emerge from these resting sites when looking for a nearby blood meal or an oviposition site, such as a bird bath or any water-holding container.
Barrier treatments with residual insecticides can be effective for reducing populations of Asian tiger mosquitoes and other mosquito species. Barrier treatments can be applied to foliage and other resting sites to control mosquitoes in the treatment area and prevent new mosquitoes from entering. Proper inspection, equipment and application techniques are critical to a successful mosquito application. These best management practices can be reviewed here.
The efficacy of a barrier spray treatment can be impacted by several factors. A recent study published in the American Journal of Mosquito Control1 assessed the effect of plant species on the residual efficacy of barrier sprays when applied under natural environmental conditions. As residential yards often contain a variety of plant species with unique physiological makeups and varying growth rates, it’s helpful to know if the residual life of a barrier spray will vary among plant types.
Laboratory assay setup. All exposures were done using glass shell vials that contained treated foliage and five mosquitoes per replication. Source: Ben McMillan, Virginia Tech, 2015
Five plant species commonly found in backyards in southwest Virginia were selected for this study:
1. Zebra grass (Miscanthus Sinensis)
2. Boxwood (Buxus)
3. Rhododendron (Rhododendron X ‘Chionoides’)
4. Arborvitae (Thuja occidentalis)
5. Japanese honeysuckle (Lonicera japonica)
While the plants had varying degrees of leaf arrangement and abundance, chemical makeup of the cuticular wax coatings and plant growth rate, the difference in efficacy after a Demand® CS insecticide application was minimal. Over eight weeks and across all plant types, Demand CS (0.06%) still provided an average mortality rate of 93.4%. This study was conducted during an exceptionally wet season as a tropical storm passed through the area, almost doubling the expected rainfall amount.
Mean % mortality (SE) of Aedes albopictus after 24-hour exposure to Demand CS-treated leaves aged out to eight weeks in the field
Demand CS concentration (%)
94.3 (1.8) a
99.5 (0.5) a
86.7 (3.5) a,b
95.2 (2.3) a,b
84.8 (3.4) a,b
94.8 (1.8) a,b
72.9 (5.4) b,c
92.9 (2.9) a,b
59.0 (9.0) c
84.8 (5.6) b
Means within each column followed by the same letter are not significantly different. Tukeys HSD test (P > 0.05).
The high level of control on all plant types during the eight-week study can likely be attributed to using proper equipment and products. Demand CS is a microencapsulated formulation containing the active ingredient lambda-cyhalothrin. It is formulated with iCAP™ technology, which contains dual-walled microcaps that can help protect the active ingredient from degradation on hostile surfaces, yet still be biologically available to the insect.
As you gear up for mosquito season, keep in mind that mosquito control is a multi-pronged approach, including breeding site removal and treatment, adulticide applications and customer communication and education. To give you a competitive advantage, Syngenta offers the SecureChoice℠ Mosquito Assurance Program for proven mosquito control. With the combination of Demand CS and Archer® insect growth regulator, this program can help reduce mosquito populations for up to 60 days and free up technician time. The program also offers materials for homeowners about how to reduce breeding sites and how to protect themselves from mosquito bites.
With mosquito season upon us, it’s important to be properly prepared so you can make effective barrier treatments for your customers. For more information, please visit SyngentaPMP.com/Mosquito.
1 McMillan, BE, Bova, JE, Brewster, CC, Gallagher, NT, Paulson, SL. Effects of plant species, insecticide, and exposure time on the efficacy of barrier treatments against Aedes albopictus. J Am Mosq Contr Assoc. 2018:34:281–290.
All photos are either the property of Syngenta or are used with permission.
Performance assessments are based upon results or analysis of public information, field observations and/or internal Syngenta evaluations. Trials reflect treatment rates and mixing partners commonly recommended in the marketplace.
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