Influence of abiotic factors on two spotted spider mite population in eggplant

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1 Influence of abiotic factors on two spotted spider mite population in eggplant S. Vinoth Kumar 1, C. Chinniah 2, C. Muthiah 2 and P. Sivasubramanian 1 1 Department of Agricultural Entomology, TNAU, Coimbatore , T.N., India 2 Department of Agricultural Entomology, Agricultural College and Research Institute Brinjal is one of the most important vegetable crops. The arthropod pests attacking brinjal, the two spotted spider mite, Tetranychus urticae is one of the important pests devastating the productivity of the crop. The indiscriminate use of chemical pesticides has resulted in three major consequences i.e. resistance development in insects and mites to insecticides/ acaricides, resurgence of pests and accumulation of residues in the environment and food grains (Balasubramani and Swamiappan, 1993). It becomes paramount important to monitor the population build-up of mite as influenced by weather factors, so that suitable management strategy could be devised when such a favorable climatic change occur besides forecasting the occurrence of mite. Brinjal crop (MBH-11) was raised in field. The population of mites was monitored in unprotected condition during October 2008 to April 2009 at Chekkanurani village, Madurai. The population was observed at weekly intervals from ten randomly selected plants/ 3 leaves/plant/2cm² area/ leaf using a 10x hand lens. The weather parameters viz., maximum temperature; Madurai , t. N., India vinothsubbaiah@gmail.com minimum temperature, relative humidity, rain fall, wind velocity and sun shine hours etc., were recorded on daily basis for correlation-regression analysis. Maximum temperature had significant positive correlation (r = ) with two spotted spider mite population. Relative humidity (r = ) and rainfall (r = ) had a significant negative correlation with two spotted spider mite population. Similar results were obtained by Chinniah et al., (2007). Silva et al. (1999) also proved that the increase in population of T. ludeni occurred at 25 o C. Rainfall contributed to the low population of two spotted spider mite (Bhagat and Singh, 1999). Baradaran et al. (2001) proved that the female mites diapaused when the temperature was below 15 o C. The minimum temperature, wind velocity and sunshine hours had no significant effect on the population dynamics of two spotted spider mite. Two spotted spider mite, Tetranychus urticae happened to be one of the major pests of brinjal at several locations of important vegetable growing tracts. Its distribution and abundance had been reported from vegetable growing tracts of Punjab and Haryana (Rachna Gulati, 2004). Krishna Rolania and Sharma (2007) also confirmed 246

2 that the population of T.urticae on Ashwagandha peaked the third week of December due to fairly high temperature. The population declined from last week of December to negligible level in the third week of January due to high RH and rainfall. low temperature and high relative humidity. However, the population shot up during the last week of January and towards April (42 to 58 mites per 2cm 2 ) because of high temperature and low RH. This is in conformity with Bhagat and Singh (1999) on brinjal. In the first season (Oct 2008 to Jan 2009); the incidence of two spotted spider mite, T. urticae (Figure 1) was moderate due to moderate temperature and slightly higher relative humidity. The mite population density was 7 to 10 per 2cm 2 of leaf. This finding is in confirmity with the findings of Rachna Gulati (2004) who also observed the peak population of T. urticae during October at Hisar (Haryana). Chinniah et al. (2007) also reported similar trend on okra. According to them the peak population of T.urticae was observed during kharif in Madurai on okra. However, from second week October the mite population declined due to heavy rainfall. Bhagat and Singh (1999) have also confirmed that the mite population remained high during August to February on brinjal, due to congenial weather factors. Mani et al. (2007) reported that T. urticae population on Grapevine increased in December and reached peak in April at Pune. With reference to the second season (Jan 2009 to Apr 2009), the incidence of T. urticae was found gradually increasing from January to April because of a steady and gradual increase in temperature and reduction in relative humidity. Initially it was low during the first fortnight of From the linear regression equations fit, (Table 2) it is inferred that an increase in maximum temperature by 1 o C there was a proportionate increase of two spotted spider mite population by %. Nevertheless for an increase in relative humidity by 1 % there was a decrease in mite population by %, and for every 1 mm increase in rainfall, the mite population declined by %. Simple correlation worked out with other abiotic factors revealed no significant impact on population of spider mites. CONCLUSION The study conducted to determine the influence of weather parameters on population of two spotted spider mite, T. urticae in eggplant showed that the mite population was positively correlated with maximum temperature and negatively correlated with relative humidity and rainfall. Minimum temperature, wind velocity and sunshine hours had no significant effect on the population dynamics of two spotted spider mite. Environmental conditions were used to develop prediction models for two spotted spider mite infestation. January (10 to 14 mites per 2cm 2 ), due to 247

3 Table 1: Influence of abiotic factors on population of two spotted spider mite on brinjal October 2008 April 2009 Month / std. week Mite population per 2cm 2 leaf area (mean of three replications) Month/ std. week Mite population per 2cm 2 leaf area (mean of three replications) Oct Jan Oct Jan Oct Jan Oct Jan Nov Jan 31 Feb Nov Feb Nov Feb Nov Feb Nov 29-Dec Feb 28-Mar Dec Mar Dec Mar Dec Mar Dec 27-Jan Mar 28-Apr

4 Table 2: Influence of abiotic factors on population of two spotted spider mite on brinjal Pest Correlation Temperature ( 0 C) Maximum Minimum Relative humidity (%) Rainfall (mm) Sunshine hours Wind velocity (Km/hr) r r 2 (r) Brinjal two spotted spider mite Y = a + bx X X X X X X Significance P = 0.05 * * - * * - - Non Significance - NS - - NS NS 249

5 REFERENCES Balasubramanian, V. and Swamiappan, M., Screening of insecticides used in cotton ecosystem for their effect on the green lacewing, Chrysoperla carnea Stephens (Neuroptera: Chrysopidae) Proceedings of National Symposium on Advances in biological control of insect pests, 2-4, Oct, Uttar Pradesh Zoological Society, Sanatan Dharam College, Muzuffarnagar, Uttar Pradesh, India. pp. 30. Baradaran, P., Arbabi, M., Kamali, K. and Ostovan, H., Study on biology of T. cinnabarinus (Boisd.) on ornamental plants under laboratory conditions. Appl. Entomol. Phytopathol., 69(1): Bhagat, K. C. and Singh, W., Some observations on the biology and behaviour of carmine spider mite, Tetranychus cinnabarinus (Boisduval) (Acarina: Tetranychidae) a pest of brinjal vegetable. J. Adv. Zoology., 20(1): Chinniah, C., Balaji, S., Kanimozhi Maragatham, K. and Muthiah, C., Influence of weather parameters on the population dynamics of red spider mite Tetranychus urticae on okra Abelmoschus esculentus (L.) Moench. J.Acarol., 16: Eswara Reddy, S. G., Comparison of pest incidence and management strategy in capsicum and tomato grown under protected and open field cultivation. Ph.D. Thesis submitted to University of Agricultural Science. Bangalore. Krishna Rolania and Ashok Sharma, Seasonal abundance of Tetranychus urticae Koch on Ashwagandha. J. Acarol., 16(1&2): Mani, M., Kulkarni, N. S. and Venugopalan, R., Role of weather factors in the population fluctuation of the two spotted red spider mite Tetranychus urticae Koch (Acari: Tetranychidae) on Grapevine in Maharashtra. J. Acarol., 16(1&2): Rachna Gulati, Incidence of Tetranychus cinnabarinus (Boisd.) infestation in different varieties of Abelmoschus esculentus (L.). Ann. Pl. Prot. Sci., 12(1): Silva, C. A. D. da., Cordao-Sobrinho, F. P. and da Silva, A. D., Biology and thermal requirements of red spider mite, Tetranychus ludeni Zacher (Acari; Tetranychidae) on cotton. Anias II. Congresso. Brasileiro de Algodao. O. algodao no seculo XX, prespectivas. Para. O. seculo., 21: Disclaimer: Statements, information, scientific names, spellings, inferences, products, style, etc. mentioned in Current Biotica are attributed to the authors and do in no way imply endorsement/concurrence by Current Biotica. Queries related to articles should be directed to authors and not to editorial board