COMPARATIVE BIOLOGY AND MANAGEMENT OF TWO-SPOTTED SPIDER MITE, TETRANYCHUS URTICAE KOCH (ACARINA: TETRANYCHIDAE) ON COUNTRY BEAN

Abstract

The two-spotted spider mite, Tetranychus urticae Koch (Acarina : Tetranychidae) is one of the most destructive cosmopolitan pests, which attack many vegetables, horticultural and greenhouse plants. Biological performance of this mite was studied on five country bean varieties (Lablab purpureus L.) to find out the mite tolerance varieties. IPSA 2, BARI seam 1, BARI seam deshi, Deshi (Local variety) and ASA purple varieties of bean were tested under laboratory conditions (26 - 32°C, RH 70 - 85% and 13: 11 D:L). The longest longevity period was 15.63 and 19.83 days for female and male, respectively when the 7. urticae fed on ASA purple. On the contrary, it was the shortest 13.82 and 15.75 days for both the sexes while reared on BARI seam 1. Lifetime fecundity was also the highest (78.93 + 4.26) on ASA purple and the lowest (54.64 + 7.85) on BARI seam 1. The sex ratio (proportion of male) was the maximum (0.39) on Deshi (Local variety) and the lowest (0.17) on BARI seam 1. No significant differences have observed among the immature development and adult longevity of two-spotted spider mite while fed five bean varieties. But life time fecundity showed the signifcant differences on the tested hosts. Life table parameters were analyzed and found the lowest generation time (7= 12.46) when T. urticae fed on BARI seam deshi, but R, (56.60) was the highest on ASA purple, rm (0.32) and A (1.38) were also the highest when fed BARI seam deshi. Based on the fecundity performance of two-spotted spider mite, it could be concluded that the variety BARI seam 1 was less preferable host as compared to others. A comparison was made for studying the effect of some pesticides: Omite 57 EC, Kumulus DF and botanical oils: neem oil, mahogony oil, chilli extract and water on the important mite pest, Tetranychus urticae. The sublethal concentrations of Omite 57 EC (20 ml/10L), Kumulus DF (4.5 gm/1L), neem oil (5 ml/1L), mahogony oil (5 ml/1L) and chilli extract (10 gm/1L) were used. The test was conducted in both the semi-field (25-34°C, 65-80% RH and a photoperiod of 13L: 11D) and laboratory (26 - 32°C, 70 - 85% RH and a photoperiod of 12 - 13: 12 - 11 L: D) conditions using bean variety IPSA 2 with three replications. Results showed that the highest mortality caused by Omite 57 EC (96.37%, 100%, 99.62%, 100% and 100%), while the lowest mortality in water (23.22%, 2.13%, 0.01%, 3.71% and 0.00%) and control (0.00%) in the field direct toxicity assays after 1°, so 14™ and 21‘ days of spraying. I