Abstract
BackgroundBean thrips, Megalurothrips distalis (Karny), are a serious insect pest of mung bean grown in summer season as a catch crop in wheat–rice cropping system in North West India. Severe incidence leads to flower shedding and fewer pods leading to loss in grain yield. Field studies were conducted to evaluate the efficacy of horticultural mineral oils, neem-based botanicals, and pongamia soap in the form of spray in comparison to the insecticide dimethoate in 2018 and 2019.Main bodyRandomized complete block design (RCBD) was used with 11 treatments including untreated control in 3 replications. Neem seed kernel extract (NSKE) at 5% gave the highest mean percent reduction in the number of thrips (90.44 and 79.59%), followed by 10 ml l−1 of Neem Kavach 1500 ppm (85.55 and 78.97%) and the insecticide dimethoate 30% EC at 250 ml ha−1 (84.92 and 78.22%) 1 and 3 days after treatment. Neem Baan 1500 ppm, Indo-Neem 1500 ppm, and Nimbecidine 300 ppm each at 10 ml l−1 also provided 75.29–82.42% and 61.18–75.82% reduction 1 and 3 days after treatment. Horticultural mineral oils also reduced the insect population by about 64%, while pongamia soap was least effective (31.58%) among botanicals. Dimethoate 30% EC at 250 ml ha−1 recorded the highest grain yield and net returns, followed by NSKE, Nimbecidine, and Neem Kavach that were on par with it. Homemade neem extracts evaluated in 2019 caused 62.7–77.3% reduction in thrips population up to 3 days after treatment with yields comparable to 10 ml l–1 of Indo-Neem spray.ConclusionThe study indicated that neem extract was capable to manage the bean thrips in flowers of summer mung bean and obtained a high grain yield.
Highlights
Bean thrips, Megalurothrips distalis (Karny), are a serious insect pest of mung bean grown in summer season as a catch crop in wheat–rice cropping system in North West India
To overcome any negative effects resulting from use of synthetic insecticides, the study was conducted to test the efficacy of alternate strategies such as botanicals and horticultural mineral oils (HMOs) against bean thrips in mung bean
In case of water spray, thrips incidence reduced from 6.67 to 3.33, one days after treatment (DAT), and increased soon after (3 DAT) to 8.67 and to 14.00 thrips per 10 flowers up to 10 DAT, while in untreated control, there was a continuous increase in incidence on all the days of observation
Summary
Vigna radiata (L.) Wilczek, is known as a warm season grain legume crop. Verma et al (1980) reported 3 species of thrips on summer mung bean in India, viz., Frankliniella schultzei (Trybom), Thrips flavus Schrank, and Megalurothrips distalis (Karny). Some bio-rational management strategies such as botanical-based insecticides or biopesticides that are economically and environmentally safe to non-target organisms and humans are desirable for managing insect pests (Begum et al 2013). Botanicals such as neem (Azadirachta indica Juss.) and Karanj (Pongamia glabra) can be effectively used in managing pests in field crops and stored grains (Regnault-Roger and Philogène 2008). To overcome any negative effects resulting from use of synthetic insecticides, the study was conducted to test the efficacy of alternate strategies such as botanicals and horticultural mineral oils (HMOs) against bean thrips in mung bean
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