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Seasonal population dynamics of spider mite, Tetranychus ludeni Zacher (Tetranychidae) and associated predatory mite, Neoseiulus sp. nr. neoghanii (Phytoseiidae) on tomato (Solanum lycopersicum L. var. Solan gola: Solanaceae) from Himachal Pradesh, India

VIJAY SINGH and USHA CHAUHAN Department of Entomology, Dr YSP University of Horticulture and Forestry, Nauni, Solan – 173 230, Himachal Pradesh, India Corresponding author E-mail: vijay4chandel@gmail.com Seasonal population dynamics of spider mite, Tetranychus ludeni Zacher (Tetranychidae) and associated predatory mite, Neoseiulus sp. nr. neoghanii (Phytoseiidae) on tomato (Solanum lycopersicum L. var. Solan gola: Solanaceae) from Himachal Pradesh, India


INTRODUCTION
Tomato (Solanum lycopersicum L.) is an important vegetable of Himachal Pradesh and plays an important role in uplifting the economy of farmers in the state. This crop is grown on a commercial scale in the mid hill regions under protected as well as in open field. This vegetable is attacked by a number of pest species. Worldwide, more than one hundred pests have been reported on this crop (Taleker et al., 1983). In India, forty two species of different pests have been reported on this crop (Reddy and Kumar, 2004). Eight pest species were also reported on tomato and other vegetables from Himachal Pradesh (Vashisth et al., 2013). Pests not only causes major losses to the quality and quantity but act as vector of various diseases. (Dharumarajan et al., 2009). Yield loss in vegetables was approximately 9.15-100% or some time failure of the crop due to pests attack (Gupta, 1991;Prasad and Singh, 2007;Patil and Nandihalki, 2009;Vinothkumar et al., 2009).
Mites belonged to the family Tetranychidae and Eriophyidae are among the destructive pests on various crops in many parts of the world (Pokle and Shukla, 2015a). The two spotted spider mite is cosmopolitan in its distribution and reported as one of the serious pest on various crops (Manjulata et al., 2002). Introduction of high yielding varieties, improvements in cultural practices and indiscriminate use of pesticides since last three decades have made these pests become more serious . Due to their short life cycle, they are reported to develop resistance against different chemicals (Kumar et al., 2002;Sridhar and Jhansi Rani, 2003;. So, the need of need of the hour is to apply IPM practices to overcome the problem of resistance and to check the economic loss of farmers. Biological control offers an efficient alternative to check their population below economic injury level (Mahr et al., 2008). Predatory mites are reported as potential predators of spider mites throughout the world (Rachana et al., 2009;Bjorson, 2008;Zhang, 2002). But, before using these natural enemies as biological control agents, it is essential to know about their habitat and seasonal population. So, keeping this in view, the present investigation was carried out to know the seasonal incidence of spider mite and predatory mites association on tomato.

MATERIALS AND METHODS
Study was carried out during 2013 and 2014 on tomato crop (var. Solan gola) in open field at experimental farm, Department of Entomology. Seedlings were planted in the month of April for both the years and data was recorded from May to August at fifteen days interval. For data observation five plants were selected randomly. Samples of fifteen leaves from each plant were plucked and placed in polythene bag tied with rubber band. Samples were kept in refrigerator at 5 0 C overnight to immobilize the mites. Samples were observed under stereo zoom microscope (Olympus SZX 9) and only motile stages were counted carefully. Mean population and standard error of mean was calculated through one way ANNOVA.
Correlation between population dynamics and abiotic factors (i.e. average temperature and relative humidity) were carried out and correlation coefficient was calculated.

Identification
For identification, the mite specimens were mounted in a drop of Hoyer's medium on microscopic slides (Singh and Raghuraman, 2011;Jeppson et al., 1975). Slides were dried in hot air oven at 35-40 o C for 4-5 days. Specimens were observed under phase contrast microscope (Olympus SZX 41) and identification was done by following standard keys (Gupta and Gupta, 1994;Gupta, 2002Gupta, , 2003Chant and McMurtry, 2007).  The correlation study of mite population with abiotic factors viz. average temperature and relative humidity were also worked out ( Table 1). The population of T. ludeni showed a high positive correlation with temperature during the period of study however population was negatively correlated with relative humidity ( Table 1). Population of N. sp. nr. neoghanii was positively correlated with temperature for both the years but showed no correlation with relative humidity during 2013 but negatively correlated with relative humidity was observed 2014 (Table 1). Earlier, infestation of T. ludeni was reported by Sood and Kakar (1990) on Dahlia sp. from Himachal Pradesh. Rachana et al. (2009) reported two species of phytoseiid viz. Amblyseius longispinosus (Evans) and Phytoseilus persimilis A&H on okra in association with T. neocaledonicus. Population of T. neocaledonicus was high in the month of April whereas population of A. longispinosus and P. persimilis was reported during July and October. Zhang (2002) and Rachana et al. (2009) reported Phytoseiulus persimilis as natural enemies of spider mites on different vegetables but the T. ludeni population was low Pokle and Shukla (2015a) reported infestation of T. urticae on tomato under polyhouse condition from Navsari, Gujarat. During their study they observed that the maximum population of mites in the month of June and population was positively with correlated with the average temperature and relative humidity. These studies supported the present investigation. Infes-tation of A. lycopersici was reported on tomato with population peak during May month (Pokle and Shukla, 2015b). They reported a positive correlation between abiotic factors and mite population. Solangi et al. (2017) reported infestation of Eriophyes sheldoni latus Banks on tomato in Pakistan and highest population increase was observed from May and June. These studies support the present investigation.

Infestation of Tetranychus ludeni
This study will be useful in the bio control of phytophagous mites and other soft bodied pests on tomato. So, there is need to conserve and mass multiply these beneficial organisms for use in IPM programs which will reduce the use of synthetic chemicals on various crops and make the environment safe.