Biology of Aceria sp. (Acari:ERIOPHYIDAE) in Amaranthus tricolor L.and its management

Abstract

The study entitled ‘Biology of Aceria sp. (Acari: Eriophyidae) in Amaranthus tricolor L. and its management’ was carried out at Department of Agricultural Entomology, College of Agriculture, Padannakkad and farmer’s field at Thaikkadappuram, Nileshwar during 2019 – 2023, with an objective to elucidate the biology and life cycle of Aceria sp. (Acari: Eriophyidae) and interpret the nature and extent of damage caused by Aceria sp. on Amaranthus tricolor L. and to develop its management strategy. The life cycle of Aceria sp. included egg, larva, first inactive stage, nymph, second inactive stage and adult. The developmental cycle lasted for an average of 11.83 days. Egg, larva, first inactive stage, nymph, second inactive stage and adult took an average of 2.94, 1.99, 1.11, 2.69, 1.09 and 4.89 days respectively and measured an average length of 46.78, 74.54, 117.58, 153.82, 189.46 and 229.37 µm respectively. The pre – oviposition and post – oviposition was recorded as an average of 1.80 and 2.92 days respectively. The major symptoms were stunted growth, leaf crinkling and malformation, petiole elongation and fibrous shoots. Population assessment during the early season (December to mid – February) showed a gradual increase in mean population of mites from 16 in December to 73.56 in February. The late cropping season (March to May) observed its highest population mean in May (174.44). Predatory mite population gradually decreased over time. The height of the plants reduced to an average 67.38 per cent and the petiole elongated to a mean of 184.72 per cent. Leaf area reduced to 18.08 cm2, in relation to healthy leaves (25.70 cm2). The stray population of amaranthus plants grown in and around the farmers’ fields and the backyards of their houses, served as off – season host for the mite. The mites were highly host – specific, as it was not sighted in any of the collateral as well as weeds collected from the infested area. Field evaluation of different botanicals and acaricides were conducted in farmer’s field in Thaikkadappuarm. A day after the first spray, no mites were seen in plots sprayed with acaricides. Fenpyroximate (T2) sprayed plots observed a significant reduction in average population in the third (0.223), fifth (2.557), seventh (6.000) and fourteenth (13.553) days after spray. The second application of treatments observed a variable result, in which spiromesifen was superior to the others in the third (1.443) and fourteenth days (11.890). On the fifth day, wettable sulphur (4.333) and on the seventh day, fenpyroximate (7.113) recorded the least population mean. The analysis of pesticide residue conducted on samples sprayed with spiromesifen and fenpyroximate, on the fifth, seventh and tenth days after spray, resulted in detection of fenpyroximate at the rate of 0.29 mg per kg, 0.30 mg per kg and 0.29 mg per kg, respectively. Spiromesifen residues were not detected in the analysis.