Biorational management of maize fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) using Bacillus thuringiensis (Berliner) enriched with chemical additives

Abstract

An invasive pest, fall armyworm, Spodoptera frugiperda (J.E.Smith) (Lepidoptera: Noctuidae) attacks maize at every stage of development, from seedling emergence up to cob formation. Early instar larvae were seen mostly on leaves of maize with characteristics pin or shot hole symptoms. Later instar larvae were confined to deep whorls, leaving typically ragged like appearance and fed on the reproductive stage of the crop especially tassels and developing cobs resulting in quality and quantity loss of maize produce. The effect of commercially available Bacillus thuringiensis subsp. kurstaki product, Dipel® against the second instar larvae of Fall Armyworm (FAW )was not promising under laboratory conditions. Hence, an effort was made to add an adjuvant along with B. thuringiensis to increase the virulence of commercially available B. thuringiensis.The Laboratory bioassays with B. thuringiensis and seven chemical additives ( T1- Bt + Boric acid, T2- Bt + Zinc oxide, T3- Bt + Sodium nitrate, T4- Bt + Peptone, T5- Bt + Urea, T6- Bt + EDTA, T7- Bt + Citric acid & T8- Bt alone T9- Control) were tested against second instar larvae of Spodoptera frugiperda larvae. The results showed that B. thuringiensis plus sodium nitrate (T3) promoted maximum mortality 82.2 per cent with a minimum LC50 value of 54.620 mg/l. Sodium nitrate boosted B. thuringiensis activity at a concentration of 0.05 per cent by 2.128-fold than B. thuringiensis alone. Overall, sodium nitrate improved the efficacy of B. thuringiensis spray at the maximum level followed by boric acid, urea, EDTA and peptone.

Effects of Various Salts on The Efficacy of Bacillus thuringiensis against the Larval Instar of Fall Armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

“…Zhang, et al (2013) pointed out that many inorganic salts can increase the activity of Bacillus thuringiensis against P. xylostella larvae at different levels when combined with them, as he found calcium salts (calcium hydroxide, calcium chloride, calcium carbonate and calcium sulfate) have the preference increasing the activity of B. thuringiensis, followed by some other salts such as Sodium carbonate, potassium hydroxide and sodium acetate. Priyanka, et al (2021) indicated that treatments of B. thuringiensis in addition to inorganic salts were significantly effective against fall armyworm larvae compared with B. thuringiensis alone.…”