Submitted to: American Mosquito Control Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2007
Publication Date: 6/30/2007
Citation: PELIZZA SA, LÓPEZ LASTRA CC, BECNEL JJ, BISARO V, GARCÍA JJ (2007) BIOTIC AND ABIOTIC FACTORS AFFECTING LEPTOLEGNIA CHAPMANII INFECTION IN AEDES AEGYPTI. Journal of the American Mosquito Control Association: Vol. 23, No. 2 pp. 177–181. Interpretive Summary: Naturally occurring parasites of mosquitoes are under study to evaluate and develop these disease causing organisms as biological control agents. In this collaborative study with researchers from Argentina, a new isolate of a fungal pathogen of mosquitoes has been isolated. This investigation has been conducted to define key biological characteristics of this pathogen to enhance evaluation as a biological control agent of mosquitoes.
Technical Abstract: The effects of water volume, container surface area and the density of hosts and fungal zoospores on the infectivity of the oomycete fungus, Leptolegnia chapmanii Seymour to Aedes aegypti (L.) were investigated in the laboratory. Late third or early fourth instar larvae from a laboratory colony of Ae. aegypti were used as hosts in all assays. Fourth instar larvae of Ae. aegypti infected with L. chapmanii 48 h post-exposure (6,1 ± 0,2 x 104 zoospores per larva) were used as inoculum. Mortality rates were greater than 90% in containers with 20 or less larvae when exposed to one L. chapmanii infected Ae. aegypti larva and decreased to 37% in containers with a density of 60 larvae at 48 h. Mortality rates varied from 82% to 92% when healthy fourth instar larvae were exposed to 1 and 2 infected larvae after 48 h, respectively, while mortality of 100% was obtained with 3 and more infected larvae in the same time period. Infection rates and larval mortality in containers with variable volume from 300 to 5000 ml and similar water surface area (397 cm2) varied from 89% to 92% at 48 h post treatment, respectively. When water volume was constant (250 ml) in containers with variable surface areas (14.5 cm2 to 875 cm2) larval mortality varied from 96% to 25% after 48 h, respectively. This study has determined that the ability of L. chapmanii to infect mosquito larvae is not only dose dependent but also influenced by larval density and surface area.