Mungbean Vigna radiata (L.) R. Wilczek is a significant pulses crop in India and several other countries. The broad mite, Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae), a common polyphagous pest, has assumed the status of a major mungbean pest in India. However, there is a paucity of literature on the occurrence of broad mite on mungbean. Therefore, three experiments were conducted to determine population fluctuation of P. latus on mungbean, crop yield loss due to its infestation and susceptibility to different acaricides. The first experiment was carried out on 400 m2 area to study the population trend and the mite population was recorded weekly in 1 cm2 leaf area on fully expanded apical trifoliate leaf of thirty plants under a stereoscopic binocular microscope in laboratory. The second experiment was carried out in six pairs of plots to estimate the yield loss by comparing the yield of six plots treated with diafenthiuron 50% WP to prevent mite infestation with the yield of the other six plots kept untreated to allow normal mite infestation. The third experiment was carried out in a randomized complete block design with seven acaricidal treatments and one control, each with three replicates and the mite population was recorded in 1 cm2 of leaf area on fully expanded apical trifoliate leaf of ten plants under a stereoscopic binocular microscope in laboratory one day before and 1, 3, 5 and 7 days after each spray. The results revealed that the highest mite population (22.2 ± 0.9 mites per cm2 of the leaflet) was observed during the 15th standard meteorological week (9–15 April), 36 days after sowing at the flowering stage and then decreased till the 20th standard meteorological week (14–20 May) at the maturity stage. Correlation analysis showed that the low variation in weather parameters (temperature, relative humidity and bright sunshine hours) did not influence the P. latus numbers on mungbean to a considerable extent. The population of P. latus on mungbean was found to have a considerable impact on the yield of the crop. The estimated loss in yield due to infestation by P. latus was 37.9 ± 2.8%. Among the seven acaricides tested at flowering stage, dicofol 18.5% EC, spiromesifen 22.9% SC and diafenthiuron 50% WP showed greater efficacy against P. latus with lower seed yield loss than other acaricides. Therefore, the present study validates the efficacity of these acaricides to successfully reduce P. latus population in mungbean crop at the early reproductive stage of crop growth, thereby ensuring the successful flowering and fruit setting of the crop and reducing yield loss.
Bhowmik et al. (Mon,) studied this question.