Persistence of azadirachtin A and B in soil: Effects of temperature and microbial activity

Abstract

The persistence of two insecticidally active compounds from the neem tree, azadirachtin A and B, was determined at two different temperatures (15 and 25°C) in the laboratory after application of the commercial neem insecticide, Margosan-O, to a sandy loam soil. The influence of microbial activity on degradation was also examined by comparing autoclaved and non-autoclaved soils also at 15 and 25°C. Temperature influenced degradation rates. The DT 50 (time required for 50% disappearance of the initial concentration) for azadirachtin A was 43.9 and 19.8 d for non-autoclaved soil kept at 15 and 25°C, respectively. The DT 50 for 685 686 STARK AND WALTER azadirachtin B was 59.2 and 20.8 d for non-autoclaved soil kept at 15 and 25°C, respectively. Microbial activity was also responsible for faster degradation because DT 50 'S for autoclaved soil were much longer than for non-autoclaved soils. DT 50 ' S for azadirachtin A in autoclaved soil were 91.2 (15°C) and 31.5 d (25°C). DT50'S for azadirachtin B in autoclaved soil were 115.5 (15°C) and 42.3 d (25°C). Two degradation products of azadirachtin were detected, but were not identified. Higher levels of the two degradation products were detected in nonautoclaved soil.

Systemic applications of azadirachtin in the control of Corythucha ciliata (Say, 1832)(Hemiptera, Tingidae), a pest of Platanus sp.

“…Thus azadirachtin application using the root system of plants (Pavela et al 2004;Pavela & Teixeira da Silva 2006) or using injections (Pavela & Bárnet 2004;Kreutzweiser et al 2011) seems to be much more advantageous in terms of both efficiency and persistence, as well as the simple mode of application. In addition, there is no risk that the plant residues will have a significant negative impact on non-target organisms, provided that dosages lower than 0.2 g a.i./ cm dbh are adhered to (Stark & Walter 1995;Kreutzweiser et al 2011). In general, some of the synthetic insecticides have been recommended for systemic applications.…”

Insecticidal Efficacy of Azadirachta indica, Nucleopolyhedrovirus and Chlorantraniliprole Singly or Combined against Field Populations fo Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

“…Over the last three decades, Azadirachta indica A. Juss (neem) has received attention all over the world (Stark and Walter, 1995;Nathan and Kalaivani, 2006). The major constituent of neem is azadirachtin (AZA), which affects the feeding, growth, molting, and reproduction of insects (Kumar et al, 2008), and may be combined with other bio-based insecticides (Koppenhöfer and Kaya, 2000).…”

Antimicrobial Activity of a Neem Cake Extract in a Broth Model Meat System

“…However, whereas in neem oil azadirachtins account for the main constituents, in neem cake salannin is predominant. Attention on neem cake was so far focused on soil microflora effects, due to its predominant use as a fertilizer [31,32,33]. This study, owing to its low cost and the antimicrobial potentiality of neem, considered a selected neem cake extract as a model for exploring antibacterial, the use of natural substances as well as their derived commercial products, with a view to mass treatment of meat products.…”