Sensitivity of some nitrogen fixers and the target pest Fusarium oxysporum to fungicide thiram

Abstract

Sensitivity of some nitrogen fixers and the target pestFusarium oxysporumto fungicide thiramThis study was carried out to investigate the toxic effects of the fungicide thiram (TMTD) against five nitrogen fixers and the thiram target pestFusarium oxysporumunder laboratory conditions. Nitrogen fixing bacteriaFalvobacteriumshowed the highest values of LD50and proved to be the most resistant to the fungicide followed byFusarium oxysporum, whilePseudomonas aurentiacawas the most affected microorganism. LD50values for these microorganisms were in 2-5 orders of magnitude lower in comparison with LD50value forFusarium oxysporum. Thiram was most toxic toPseudomonas aurentiacafollowed byAzospirillum. The lowest toxicity index was recorded forFusarium oxysporumandFlavobacterium. The slope of the curve forAzomonas, Fusarium oxysporumandFlavobacteriumis more steep than that of the other curves, suggesting that even a slight increase of the dose of the fungicide can cause a very strong negative effect. Thiram was more selective toPseudomonas aurentiacafollowed byAzospirillum, Rhizobium melilotiandAzomonas. The lowest selectivity index of the fungicide was recorded forFalvobacteriumfollowed byFusarium oxysporum. The highest safety coefficient of the fungicide was assigned forFlavobacterium, whilePseudomonas aurentiacashowed the lowest value.