Pesticide effect on qualitative occurrence and survival of soil blue-green algae in laboratory condition

In the present exploration, stock solutions of Furadan (carbofuran, 3% G) and Rogor (dimethoate, 30%) pesticides were prepared and added to the BG-11 culture media to obtain the desired concentration of 100, 250, 500 and 1000 ppm. 10 g proportion of air dried soil was taken in sterilized BG-11 medium (with different concentration of various pesticides) and incubated at 28 0 ± 2 C under 16/ 8 hours light/ dark cycles with 2- 5 K Lux light intensity. The algal forms appearing in the culture flask were identified by using standard monographs after 30 days of incubation. A sum of 19 Cyanophyceae species appeared in the composite soil of the control flask belonging to 14 genera and 6 families. The occurrence of blue-green algae remained almost unaffected even in the presence of Furadan and Rogor pesticides at 100 ppm dose in the test soil. The survival percentage of bluegreen algae was reduced upto 50% at 500 ppm of Furadan while 10.52% survivability was noticed with Rogor only at 500 ppm dose level. The organophosphate, Rogor, was comparatively more toxic than carbamate, Furadan against tested blue-green algae. However, higher concentration of these pesticides significantly affects the survival showing high algicidal potential. The result of the present study revealed that indiscriminate use of these pesticides may cause adverse effects on the nitrogen fixing blue-green algae in crop fields, which has a direct effect on total productivity. The sensitivity of different Cyanophyceae to pesticide application was found more predominantly in sheath less heterocystous and unicellular forms than the heterocystous ensheathed and nonheterocystous ensheathed forms.