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The broad mite, Polyphagotarsonemus latus (Banks), is an important phytophagous mite that causes extensive damage to a wide range of crop species across the world. Fenazaquin, a mitochondrial electron transport inhibitor (METI), is one of the commonly used acaricides for the management of P. latus. The response to fenazaquin selection over generations and the risk of development of resistance was estimated herein using a laboratory‐selected population of P. latus (FEN‐SEL). Repeated exposure to fenazaquin over generations resulted in decreased susceptibility (99.32 folds) as compared to the unselected counterpart. FEN‐SEL took 26 generations for a 10‐fold increase in resistance with a realized heritability (h2) of 0.12 which indicated a low genetic variation and high phenotypic variation. Over a selection intensity of 20%–80% mortality, the generations required for a 10‐fold increase in LC50 for fenazaquin were 14.21–55.75, 7.75–30.41 and 5.33–20.91 at h2 values of 0.12, 0.22 and 0.32, respectively, with a constant slope of 2.39. The FEN‐SEL population also exhibited moderate levels of cross‐resistance to diafenthiuron, dicofol and spiromesifen and low cross‐resistance to propargite. The findings suggest a rational and rotational application of fenazaquin in the field to delay the development of resistance and to prolong its efficacy against P. latus. [ABSTRACT FROM AUTHOR]

The broad mite, Polyphagotarsonemus latus (Banks), is a cosmopolitan pest that attacks a wide range of economically important crops like hot and sweet peppers, mulberry, 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 population (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 spiromesifen. 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. [ABSTRACT FROM AUTHOR]

The broad mite, Polyphagotarsonemus latus (Banks), has assumed a key pest status in several crops like chilli, capsicum, mulberry, jute, tea, sesame and cotton in recent years. In spite of the increasing cases of outbreaks and reports of chemical control failures, the prevalence of acaricide resistance in broad mite remains under studied. In this context, five major acaricides were used to ascertain the resistance development in three field-collected populations of broad mite from Karnataka. A laboratory strain (NBAIR-GR-TAR-01a) of broad mite being maintained at ICAR-NBAIR showed high susceptibility to propargite 57 per cent EC (LC50 of 0.37 ppm), diafenthiuron 50 per cent WP (0.40 ppm), fenazaquin 10 per cent EC (0.44 ppm), spiromesifen 22.9 per cent SC (0.58 ppm) and dicofol 18.5 per cent EC (0.70 ppm). Among the field populations screened, the Haveri population showed higher resistance to the tested acaricides as compared to Chikkaballapur and Tumkur populations. Upon categorizing the resistance levels, resistance to spiromesifen was observed to be extremely high (162.55folds) in broad mites collected from Haveri on chilli crop. The acaricide which recorded the lowest levels of resistance was propargite (8.81 folds) in Tumkur population. Dicofol and fenazaquin registered moderate to high levels of resistance, while diafenthiuron recorded high levels of resistance across the populations studied. [ABSTRACT FROM AUTHOR]

Cowpea [Vigna unguiculata (L.) Walp.] is one among the premier pulse crops grown across the world as vegetable, fodder and for seed purpose. Inspite of the various economic and nutritional benefits of cowpea, its full yield potential is hardly ever realized due to the interaction of several factors, of which bruchid infestation is considered to be very important. In this context, 15 cowpea genotypes were screened to document their varietal reaction. Upon categorising the genotypes, none of the test accessions were found highly resistant. The accessions which recorded the least per cent damages at 90 DAR, i.e., GC-3, IC 202702, IC 259065 and DC-15 fell into the grade moderately resistant (MR) to Callosobruchus chinensis (L.) in storage. The genotypes IC 6202, IC 998326, IC 259106 and IC 91556 were registered as least susceptible (LS) genotypes. The genotypes IC 219871, IC 198383, IC 253272, IC219594 and DCS 47-1 were categorised as moderately susceptible (MS) whereas IC 253276 and IC 257407 fell into the pest reaction grade of highly susceptible (HS). There was a negative and significant correlation between per cent damage and phenol content of the seeds whereas the moisture and protein of seeds were positively correlated with per cent damage at 90 days after release. [ABSTRACT FROM AUTHOR]

Cowpea [Vigna unguiculata (L.) Walp.] is one among the chief pulse crops grown around the globe. As a pulse crop, it fits well into most of the cropping systems. i.e., as sole crop, mixed crop, intercrop and in agro-forestry combinations. Among the different factors that detains cowpea from realizing its full yield potential, the infestation of the bruchid, Callosobruchus chinensis (L.) assumes much importance. In this background, 15 cowpea genotypes were tested for their oviposition preference and it was correlated with the seed morphological characters. The mean number of eggs laid per 20 seeds on different cowpea entries varied from 9.00 to 19.00. The genotype IC 253272 received the highest number of eggs (19.00) which was on par with the entries IC 253276 and IC 998326, which recorded 18.50 and 17.50 eggs, respectively. On the other hand, the genotypes GC-3 and IC 91556 received the least number of eggs (9.00 each) which were on par with genotypes IC 259065 (10.00 eggs) and IC 202702 (10.50 eggs).The selected genotypes varied in terms of their seed size, colour and shape.A positive and non-significant correlation was observed between oviposition preference and seed size; while there was a negative and non-significant correlation in terms of seed colour and seed shape. [ABSTRACT FROM AUTHOR]