www.IndianJournals.com Members Copy, Not for Commercial Sale Downloaded From IP - 14.139.224.82 on dated 28-Dec-2012 J.K. Bana, B.L. Jat and D.R. Bajya 348 Ann. Pl. Protec. Sci. 20 (2) : 348-350 (September, 2012) Impact of transplanting dates on incidence of major insect pests of Cabbage J.K. Bana, B.L. Jat and D.R. Bajya Department of Agricultural Zoology & Entomology, S.K.N. College of Agriculture, Jobner, Jaipur-303 329, India <jugalbana@gmail.com> Date of Receipt: 22.05.2012; Accepted: 01.08.2012 ABSTRACT The minimum infestation of aphid and larval population of diamondback moth was recorded on early crop transplanted on 26 th September followed by 3 rd and 10 th October transplanted crop and maximum infestation was on late crop transplanted on 24 th October. Highest yield of cabbage heads was obtained from the crop transplanted on 10 th October, while minimum yield was in late transplanted crop. The aphid and larval population of diamondback moth had significant positive correlation with transplanting dates of cabbage crop. On the other hand, the transplanting date and incidence of aphid and diamondback moth showed significant negative correlation with the yield of cabbage heads means, with the delay in transplanting, dates incidence of pests increased and yield of cabbage heads decreased. Key words: Lipaphis erysimi, Plutella xylostella, Transplanting date. Cabbage is one of the most important vegetable crops grown more or less in all the states of India, and attacked by a number of insect pests, but aphid, Lipaphis erysimi (Kalt.) and diamond back moth, Plutella xylostella (L.) are reported as major pests in semi-arid region of Rajasthan, causing significant losses ( Meena et al., 2011). Hence, the present investigation was conducted to determine the impact of transplanting dates on incidence of major insect pests of cabbage. Materials and Methods The field trial was conducted at S.K.N. College of Agriculture, Jobner during rabi, 2008- 2009 and 2009- 2010, was laid out in with five treatments (transplanting dates) and four replications. The plot size was 2.25 x 2.25 m with row and plant distance of 45 x 45 cm, respectively. The estimation of aphid population was based on the numerical count method. Total number of aphids on five plants were counted visually with the help of magnifying lens at weekly interval. For recording the aphid population at early plant stage, leaves were grasped at the petiole by thumb and four fingers and twisted until entire underside of the leave clearly visible. To estimate the larval population of DBM, direct visual counting method was used. The data on aphid and larval population of DBM moth were transformed. The following formula was used for calculating. N xy - (x) (y) r = N x 2 - (x) 2 . N y 2 - (y) 2 where, r = Simple correlation coefficient x = Independent variable i.e. abiotic component y = Dependent variable i.e. pest N = Number of observations Results and Discussion Data on the effect of transplanting time on incidence of insect pests of cabbage indicated that 