Effect of binary mixtures of Profenofos and Lufenuron with Bacillus thuringiensis formulation against Spodoptera exigua Hbn. in the laboratory

anglais. A laboratory study was carried out at Brebes (Central Java) since October to November 1996 to test the effect of binary mixtures between formulations of Profenofos or Lufenuron with Bacillus thuringiensis var. kurstaki against second-third instar larvae of beet armyworm, Spodoptera exigua Hbn. The three compounds (Profenofos, Lufenuron and B. thuringiensis) was initially tested to evaluate its efficacy against S. exigua larvae and to determine their LC50 values. The later test was conducted to evaluate the efficacy and LC50 values of binary mixtures between Profenofos or Lufenuron with B. thuringiensis at sublethal concentration against S. exigua larvae. A dipping method of shallot leaves in a dillution of concentration formulation of insecticides tested was used in this experiment. The concentration formulation of insecticides was tested to ten larvae of S. exigua (instar II-III) with four replications. Mortality of S. exigua larvae was observed at 72 hours after exposures. The mortality data were analyzed by means of the probit analysis to determine the LC50 values. Results showed that all tested mixtures of B. thuringiensis with Profenofos and or Lufenuron have sinergistic effect to mortality of S. exigua larvae. Based on LC50 values insecticides mixture, the addition of B. thuringiensis to Profenofos and or Lufenuron increased the effectiveness by 27 and 97 fold respectively compared to Profenofos and Lufenuron alone. The results implied that application of such generated technology will reduce the use of pesticides and residue

indonésien. Percobaan di laboratorium telah dilakukan di Brebes (Jawa Tengah) sejak bulan Oktober sampai November 1996 untuk mengetahui pengaruh pencampuran formulasi insektisida Profenofos atau Lufenuron dengan Bacillus thuringiensis var. kurstaki terhadap larva ulat bawang, Spodoptera exigua Hbn. instar II-III. Pengujian tahap pertama dilakukan untuk mengetahui efikasi dan nilai LC50 insektisida Profenofos, Lufenuron dan B. thuringiensis terhadap larva S. exigua. Pengujian tahap kedua dilakukan untuk mengetahui efikasi dan nilai LC50 campuran insektisida Profenofos atau Lufenuron dengan B. thuringiensis pada konsentrasi subletal terhadap larva S. exigua. Percobaan dilaksanakan dengan "metode pencelupan" daun bawang ke dalam larutan konsentrasi formulasi insektisida yang diuji. Masing-masing perlakuan konsentrasi formulasi insektisida diujikan terhadap 10 ekor larva S. exigua instar II-III dan diulang empat kali. Mortalitas larva S. exigua dihitung 72 jam setelah perlakuan dan penghitungan nilai LC50 menggunakan analisa probit. Hasil percobaan menunjukkan bahwa campuran insektisida Profenofos atau Lufenuron dengan B. thuringiensis mempunyai efek sinergistik terhadap mortalitas larva S. exigua. Berdasarkan nilai LC50 campuran insektisida, efikasi campuran B. thuringiensis dengan Profenofos atau Lufenuron terhadap larva S. exigua meningkat masing-masing sebesar 27 dan 97 kali lipat jika dibandingkan dengan efikasi Profenofos dan Lufenuron secara tunggal. Penerapan hasil penelitian ini akan mengurangi penggunaan insektisida dan mengurangi pencemaran lingkungan