Effect of some granular insecticides currently used for the treatment of maize crops (Zea mays) on the survival of inoculated Azospirillum lipoferum

Abstract

Four insecticides, carbofuran, chlormephos, terbufos and benfuracarb, currently used on maize (Zea mays) at sowing, were tested for their compatibility with Azospirillum lipoferum strain CRT1 used as an inoculant to improve maize growth and yield. The growth or survival of A lipoferum was studied in the presence of the insecticides: (1) in liquid and solid cultures of the bacteria, (2) when a commercial inoculant (Azogreen-m, Liphatech, Meyzieu, France) was inoculated directly on insecticide granules, (3) when inoculated Azogreen-m granules were mixed with insecticide granules and (4) when inoculated Azogreen-m granules were delivered separately to the seed bed. Of the four insecticides tested, only terbufos had a slight effect on growth of A lipoferum in solid cultures. All the insecticides decreased the survival of A lipoferum when the bacteria were inoculated directly on to the granules, or when inoculated Azogreen-m granules were mixed with an insecticide. We hypothesize that the discrepancies between bacterial culture tests and survival studies might be explained by the conditions of desiccation encountered during inoculation of the granules. Desiccation stress could increase the toxic effect of the insecticides. We therefore suggest including desiccation stress in the biotest used to assess inoculant-pesticide compatibility.

Azospirillum-plant relationships: physiological, molecular, agricultural, and environmental advances (1997-2003)

“…Of 4 insecticides (carbofuran, chlormephos, terbufos, and benfuracarb) currently used on maize at the time of sowing, only terbufos had a slight effect on growth of A. lipoferum in solid medium cultures. Physical contact of the insecticides with the commercial inoculant (Azogreen-m), bacteria inoculated directly on insecticide granules, or inoculant mixed with an insecticide all decreased survival of A. lipoferum (Revellin et al 2001).…”

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