Acaricide resistance among broad mite (Polyphagotarsonemus latus (Banks)) populations in Karnataka, India

The broad mite, Polyphagotarsonemus latus (Banks), is a cosmopolitan pest that attacks a wide range of econo-mically important crops like hot and sweet peppers, mul-berry, jute, tea and several ornamentals. This study was undertaken to monitor the development of acaricide resistance, if any, in five representative field-collected populations of Karnataka, India. Bioassays were carried out against five acaricide chemistries, and resistance ratios were calculated by comparing the LC50 values of field populations with the susceptible laboratory popula-tion (Pa-Lab). The resistance ratios varied from 26.03 to 81.16-fold for diafenthiuron, 27.35 to 83.47-fold for dicofol, 9.72 to 45.42-fold for fenazaquin, 8.77 to 16.84 -fold for propargite and 48.37 to 163.39-fold for spiro-mesifen. Resistance to the acaricides was unstable in P. latus as a decline in resistance (14.11-102.53-fold) was observed over generations in the absence of selection pressure. The results suggest that acaricides should be sprayed at economic threshold levels or on a rotation basis for one or more seasons for better management of P. latus by delaying the development of resistance.