Impact of source reduction on the spatial distribution of larvae and pupae of Aedes albopictus (Diptera: Culicidae) in suburban neighborhoods of a Piedmont community in North Carolina

Abstract

Aedes albopictus (Skuse) is a principal nuisance mosquito species and a potential arbovirus vector throughout its geographic range in the United States. This species lays eggs, and progeny complete development in water-filled containers that are discarded in suburban landscapes. Source reduction of containers, achieved through environmental sanitation, was used to experimentally manipulate mosquito production to gain insight into the spatial structure of the population of immature Ae. albopictus. Our studies were conducted in suburban landscapes in Raleigh, NC, during the 2002 and 2003 mosquito seasons. Spatial analyses, using estimates of the mean and total standing crop of pupae and counts of the numbers of mosquito-positive containers, showed that the distribution of mosquito production was not spatially dependent on a neighborhood-wide basis. However, in all neighborhoods, mosquito production was clustered in at least one and often more than one adjacent residence. Point pattern analyses that considered only the presence or absence of pupae showed that pupae-positive residences were dispersed throughout neighborhoods receiving monthly source reduction treatments and clustered throughout control neighborhoods, indicating that source reduction affected the spatial distribution of pupae. Conversely, spatial analyses based on the presence or absence of larvae and pupae showed that mosquito production was randomly distributed among residences in both control and source reduction neighborhoods, showing that Ae. albopictus recolonized containers within several weeks after source reduction was implemented. Knowledge of the spatial distribution of production sites would allow management efforts for Ae. albopictus to be targeted to residences supporting high levels of mosquito production.

Fig. 1

G_i* maps showing clustering of immature Ae. albopictus in neighborhood N-3 (No-TRT) in 2003. (A) Mean total standing crop of pupae per residence. (B) Mean standing crop of pupae per container per residence. (C) Mean numbers of pupae-positive containers per residence. (D) Mean numbers of pupae- or larvae-positive containers per residence.

Fig. 2

G_i* maps showing clustering of immature Ae. albopictus in neighborhood N-4 (No-TRT) in 2003. (A) Mean total standing crop of pupae per residence. (B) Mean standing crop of pupae per container per residence. (C) Mean numbers of pupae-positive containers per residence. (D) Mean numbers of pupae- or larvae-positive containers per residence.

Fig. 3

Results of K-function (second order) analysis of the spatial distribution of Ae. albopictus pupae-positive containers in neighborhoods not receiving source reduction in 2002, N-3 (A) and N-4 (B), and 2003, N-3 (C) and N-4 (D), and neighborhoods receiving source reduction in 2003, N-5 (E) and N-7 (F).

Fig. 4

Results of K-function (second order) analysis of the spatial distribution of Ae. albopictus larvae-positive or pupae-positive containers in neighborhoods not receiving source reduction in 2002, N-3 (A) and N-4 (B), and 2003, N-3 (C) and N-4 (D), and neighborhoods receiving source reduction in 2003, N-5 (E) and N-7 (F).

Fig. 5

Results of K-function (second order) analysis of the spatial distribution of Ae. albopictus pupae-positive containers (except tarps and bird baths) in neighborhoods not receiving source reduction in 2002, N-3 (A) and N-4 (B), and 2003, N-3 (C) and N-4 (D), and neighborhoods receiving source reduction in 2003, N-5 (E) and N-7 (F).