Relative tolerance of nitrogen-fixing blue-green algae to pesticides

Abstract

In-vitro tolerance of blue-green algae to pesticides was studied. Twenty-seven strains of nitrogen-fixing cyanophyta from four genera were tested. Commercial preparations of ceresan m, dithane, 2,4-d, delapon, propazine, cotoron, diuron, and linuron were used at concentrations varying from 0.01 to 2000 ppm. Most nitrogen-fixing blue-green algae could tolerate high pesticide levels although they showed wide variation in relative tolerance. Levels of different pesticides are described in relation to specific strains; for example, though most of the strains of anabaena could tolerate 100 ppm of ceresan, strain 310 was sensitive to a concentration of 0.01 ppm; though dithane was lethal to some strains of anabaena and nostoc at the lowest concentration used, some strains could grow well at 50 ppm. High concentrations of ceresan, dithane, 2,4-d and delapon were tolerated by tolypothrix tenuis and aulosira fertilissima. Propazine, cotoron, and linuron were lethal, and diuron lethal to both algae. Specific strains should be used with different pesticides and a mixture of different strains--not a single strain--should be used as seeding material when more than one pesticide is applied to the crop.