Plant Archives Volume 20 No. 2, 2020 pp. 3503-3509 e-ISSN:2581-6063 (online), ISSN:0972-5210 CHANGES IN HERBACEOUS COMMUNITY PATTERN, GROWTH AND BIOMASS ACCUMULATION UNDER SINGLE AND COMBINED TREATMENT OF CHLORPYRIFOS AND MALATHION INSECTICIDES Srishti Mishra, Arideep Mukherjee and Madhoolika Agrawal* Laboratory of Air Pollution and Global Climate Change, Department of Botany, Institute of Science, Banaras Hindu University, Varanasi (U.P.), India. Abstract Organophosphate pesticides are highly toxic insecticides, causing sever neurotoxic impacts on pests. Use of pesticides in agriculture is increasing to protect the food commodities from pests to fulfill the increasing food demand. Indiscriminate use of insecticides may cause negative impacts on community structure and biodiversity. The present study was conducted to assess the community composition, canopy cover, growth and biomass accumulation in herbaceous community under individual and combined treatments of Chlorpyrifos (CP) and Malathion (MT) with respect to untreated control. Jaccard and Sorenson similarity indices showed more than 50% similarity in communities under different treatments. Coronopus didymus (L.) Sm. and Oxalis corniculate L. were most dominant species in community under all the treatments. The numbers of plant species were 18, 14, 13 and 11, respectively in control, CP, MT and CP+MT treatments. Canonical discriminant analysis discriminates the effects of treatments on the growth parameters where combined treatment showed antagonistic effect, while individual treatments have similar effects. This study indicates that Chlorpyrifos and Malathion insecticides at recommended dose have potential to change species composition, growth and biomass of herbaceous community. Key words: Chlorpyrifos, Malathion, herbaceous community, growth, biomass accumulation Introduction In India use of pesticides is about 3 percent of the world uses and rate is increasing each year (Ravi and Fulekar, 2018). Many pesticides are banned, but many more numbers of pesticides are registered for agricultural uses. Uttar Pradesh state shows highest pesticide’s consumption, where uses of Malathion and Chlorpyrifos are more than seven million tons during 2005-2010 (India for safe food, 2020). Organophosphate insecticides are widely used due to its low toxicity and persistent nature as compared to organochlorine (Costa, 2006). Organophosphate insecticides are lipophilic in nature and hence adversely affect the living cell membrane (Videira et al., 2001). Ever increasing population rise and consequent demand for food, directly or indirectly leads to an increase in the use of pesticides for more crop production. But repeated uses of pesticides lead to change in biodiversity pattern, its deterioration as well as accumulation in higher trophic levels causing bio-magnification (Sitaramaraju et al., 2014). Use of pesticides causes beneficial effects on one side by reducing crop losses, preventing from vector diseases and improving the quality of food by killing the pests, but on the other side causes hazardous effects by reducing the soil fertility, increasing soil contamination, impacting on non-target organisms and contaminating the food web (Aktar et al., 2009). Use of pesticides may cause many acute and chronic residual effects on ecosystem such as negative impacts on non-target organisms even on some keystone species, which are important part of ecosystem structure and function, and promote non-essential species which may dominate due to alteration in prey and predator relationship (Sitaramaraju et al., 2014). Increasing frequency of insecticide uses severely affected the diversity of wild plants, carabid species and bird diversity compared to the organic farming (Geiger et al., 2010).An important grass, Lolium perenne and a forb, Centaurea jacea showed reductions in their growth and biomass under Chlorpyrifos insecticide treatment compared to the control due to insecticide-mediated soil feedback in form *Author for correspondence : E-mail : madhoo.agrawal@gmail.com