Piper ovatum (Piperaceae) extract/starch-cellulose films to control Aedes aegypti (Diptera: Culicidae) larvae

摘要

Most of the botanical extract which showed larvicidal properties against Aedes aegypti present low residual activity. Thus, we included Piper ovatum extract in a hydrophilic, biodegradable polymeric base to increase the time of action of these larvicides. Standardized extract of P. ovatum roots was tested against Ae. aegypti larvae in order to investigate some external morphological modification in the larvae body and histological effects in their midgut. Two films called FSEPO5 and FSEPO12 containing 5 and 12% of P. ovatum extract were incorporated into biodegradable starch-cellulose films. Loss of weight and mechanical properties were evaluated. The larvae mortality was investigated through immersion of different pieces with known width into the plastic flask containing 200 mL of water and Ae. aegypti larvae. After 48 h of exposure, the mortality was checked and new larvae were added. The experiment was conducted until no more larvae mortality was observed. The effect of the surface area-to-volume ratio over larval mortality was assessed as well. The LC50 and LC99 of P. ovatum extracts were 2.57 ppm and 3.80 ppm, respectively. The inclusion of the extract in to the film decrease the elastic modulus, increase the elongation at break and promote higher erosion. The residual activity of the films was achieved for more than 700 h (29 days). The increase in surface-to-volume ratio of the film increased the larvicidal activity. Starch-cellulose films containing standardized extract of P. ovatum is a suitable alternative to prevent mosquito breeding in places with potential water accumulation. They can provide industrial larvicide in the future.