MSc

Investigations on “Management of pests and pesticide residues in vegetable amaranth (Amaranthus tricolor L.)” were carried out at Department of Agricultural Entomology, College of Agriculture, Vellayani during 2013-15. The main objective of the work was to assess the bio-efficacy of new generation insecticides for the management of leaf feeding insect and mite pests of A. tricolor L and standardization of methods to remove pesticide residues in vegetable amaranth.
Field survey was conducted among ten farmers each from two different locations viz., Kalliyoor and Pappanchani. During survey, leaf webbers and leaf eating caterpillars were noticed as major insect pests while red spider mite was noticed to be minor pest. In these two locations, pesticides used by famers were malathion, chlorpyriphos, quinalphos, dimethoate and lambda cyhalothrin. The residues of pesticides detected in the farm gate samples collected from these locations were chlorpyriphos, quinalphos, profenophos, ethion, bifenthrin, lambda cyhalothrin, cypermethrin and fenvalerate.
Investigation was conducted on evaluation of bio-efficacy of new generation insecticides against Hymenia recurvalis and Spodoptera litura. The insecticides evaluated were chlorantraniliprole 0.006 %, novaluron 0.015 %, buprofezin 0.03 %, flubendiamide 0.0096 %, spinosad 0.015 %, emamectin benzoate 0.002 %, indoxacarb 0.015 %, thiacloprid 0.036 %, fipronil 0.01 %, Bacillus thuringiensis kurstaki 5ml L-1, Beauveria bassiana 2 %, B. bassiana (ITCC 6063) CFU - 108g -1, Oxuron - 5ml L-1, malathion - 0.1 % and neem seed kernel extract - 5 %. These insecticides were sprayed on bulk crop under field conditions, treated leaves were taken from randomly selected plants and kept in Petri plates. Second instar H. recurvalis and S. litura larvae were released into these Petri plates separately under laboratory conditions. In laboratory investigation, emamectin benzoate, indoxacarb, thiacloprid, flubendiamide, novaluron, fipronil and B. thuringiensis were found to be effective against H. recurvalis. Against S. litura, emamectin benzoate, indoxacarb, flubendiamide, novaluron and fipronil were found to be effective. Among the different treatments tested against mites, buprofezin, emamectin benzoate, spiromesifen and diafenthiuron were found to be effective. Six insecticides cum acaricides viz., buprofezin 25 SC- 0.03 %, %, emamectin benzoate 1 WG - 0.002%, diafenthiuron 50 WP - 0.06%, spiromesifen 22.9 SC- 0.018%, fenpyroximate 5 EC- 0.003% and ethion 50 EC- 0.15% were tested for efficacy against red spider mite Tetranychus spp. The best treatments identified in laboratory screening were evaluated under field conditions in two separate trials.
Field studies were conducted in famer’s field at Nedinjal and in the Instructional farm, College of Agriculture, Vellayani by using insecticides from the above effective treatments. Among the above selected insecticides fipronil, emamectin benzoate, indoxacarb, novaluron and flubendiamide were effective against H. recurvalis. Against S. litura, emamectin benzoate, indoxacarb and flubendiamide, were found to be effective. In management of mites, buprofezin and spiromesifen were found equally effective under field conditions.
Subsequent to identification of safer new generation insecticides for field level management of insect and mite pests of amaranth, a series of laboratory experiments were conducted to standardize household practices to remove pesticide residues at consumer level. The recently launched natural product “KAU Veggie Wash” was also evaluated in addition to the presently recommended consumer items from kitchen shelf. All the insecticides detected in survey of farm gate samples were selected for the study and in addition two organophosphates viz.,dimethoate representing the systemic group and malathion as insecticide check were evaluated. Among the different treatments evaluated, dipping amaranth plants in 1% KAU veggie wash (20 minutes) + cooking was found to be most effective, followed by 1% KAU veggie wash (20 minutes) + washing for removal of organophosphate and synthetic pyrethroid insecticide residues from amaranth
From the above study, it is concluded that flubendiamide 39.35% SC was the most effective and safer (green labeled) new generation insecticide in managing leaf webber (H. recurvalis), leaf eating caterpillar (S. litura) and buprofezin (green labeled) was the effective and safer acaricide for the management of red spider mite. Among ten household practices evaluated for their efficacy to remove pesticide residues from amaranth, dipping in 1% KAU veggie wash for 20 minutes followed by cooking was selected as the most effective treatment capable of significant reduction of dimethoate (86.27 %), malathion (96.47 %), chlorpyriphos (86.45 %), quinalphos (81.02 %), profenophos (76.73 %), ethion (77.11%), bifenthrin (61.03 %), lambda cyhalothrin (66.05 %), cypermethrin (62.72 %) and fenvalerate (65.07 %).
Thus it may be concluded that pests of vegetable amaranth could be efficiently managed by the application of flubendiamide 0.0096 % for insect pests and buprofezin 0.03 % for red spider mite and pesticide residues in market baskets of red amaranth can be effectively managed by dipping in KAU Veggie Wash solution @ 10 ml/L of water for 20 minutes followed by two normal washings just before cooking.