Regulation of reproduction in Rhodnius prolixus by the juvenile hormone mimic pyriproxyfen
1990
Langley, P.A. | Howl, Vanessa | Oouchi, H.
The juvenile hormone mimic, pyriproxyfen (2-[1-methyl-2-(4-phenoxyphenoxy)ethoxy]-pyridine) was 28 times more effective than S-methoprene at inducing a supernumerary moult following topical application in 1 μl acetone to 5th instar larvae of Rhodnius prolixus Stål. ED₅₀ values of 0.15 μg and 4.20 μg per insect were obtained. Adult females produced by 5th instars dosed with 0.2 μg pyriproxyfen produced nonviable eggs for at least 50 days but 1.0 μg S-methoprene was only effective for 30 days. Treatment of eggs directly required up to 10 μg pyriproxyfen in 0.2 μl acetone per egg to produce any effect on viability. Using ¹⁴C-labelled pyriproxyfen as a marker, young adult females dosed with 10 μg produced non-viable eggs when the measured radioactive content reached a peak equivalent to 40 ng intact pyriproxyfen per egg 10 days after treatment and fell to 5 ng per egg 15 days later. Egg viability did not return to normal until 70 days after treatment although virtually no radioactivity was detectable in eggs after 40 days. Prolonged exposure of adult females on filter paper perches treated with 0.15 mg pyriproxyfen in 3.5 μl oil cm⁻² reduced the viability of their eggs to zero. The effect was systemic via the adult and was not due to direct contamination of the eggs. Hence, treatment of substrates with oil formulations of pyriproxyfen should be highly effective for the control of triatomine bugs.
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