Tujuan Penelitian ini untuk mengetahui Lethal Concentration (LC50,90) dan Lethal Time (LT50,90) ekstrak rimpang alang-alang (Imperata cylindrical L.) dan daun kirinyuh (Chromolaena odorata) terhadap larva Plutella xylostella. Pengujian dilakukan dengan metode pencelupan daun (Leaf dipping methods). Larva Plutella xylostella diletakkan ke dalam toples yang akan dilaparkan terlebih dahulu selama 1 – 2 jam sebelum pengujian. Daun sawi masing-masing dicelupkan ke dalam ekstrak akar rimpang alang-alang dengan konsentrasi (0%, 0,75%, 1,5%, 2%, dan 3%) dan daun kirinyu dengan konsentrasi (0%, 1,5%, 3%, 4,5%, dan 6%), sedangkan kontrol tanpa dicelupkan kedalam ekstrak atau hanya aquades saja. Hasil penelitian menunjukkan bahwa ekstrak rimpang alang-alang lebih efektif dibandingkan dengan ekstrak daun kirinyu. Lethal concentration (LC50,90) ekstrak rimpang alang-alang dan daun kirinyuh yang dapat menyebabkan mortalitas larva P. xylostella sebesar 50% dan 90% adalah 1.34% dan 13.78% pada rimpang alang-alang sedangkan pada daun kirinyu adalah sebesar 2.91% dan 13.92%. Lethal time (LT50,90 ) ekstrak rimpang alang-alang dan daun kirinyu untuk mematikan larva 50% dan 90% adalah 135 jam dan 329 jam (rimpang alang-alang) dan 197 jam dan 533 jam (daun kirinyu).

The purpose of the research is to know Lethal Concentration (LC50,90) and Lethal Time (LT50,90) Rhizome Extract Alang-Alang (Imperata cylindrical L.) and kirinyuh leaves (Chromolaena odorata) against Plutella xylostella larvae. The test was done by leaf dipping methods. Plutella xylostella larvae were placed into a jar that will be exposed for 1-2 hours before testing. The each mustard leaves was dipped in the root extract of rhizome alang-alang with concentrations (0, 0.75, 1.5, 2, and 3%) and kirinyu leaves with concentrations (0, 1.5, 3, 4.5, and 6%), while the controls without immersed into the extract or aquades only. The results showed that rhizome alang-alang extract are more effective than kirinyu leaf extract. Lethal concentration (LC50,90) rhizome extract of rhizome alang-alang and kirinyuh leaves that can cause mortality of P. xylostella larvae of 50% and 90% is 1.34% and 13.78% in rhizome alang-alang whereas in kirinyu leaf is 2.91% and 13.92%. Lethal time (LT50,90) rhizome extract alang-alang and kirinyu leaves to kill 50% and 90% larvae are 135 hours and 329 hours (rhizome of alang-alang) and 197 hours and 533 hours (kirinyu leaves).

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