Abstract

                                Studies on biology of Phenacoccus solenopsis on leaves of Hibiscus rosa-sinensis L. were carried out in P.G. Laboratory, Department of Entomology, Navsari Agricultural University, Navsari (India) during the year 2006-07 revealed that the females laid 256.16 ± 133.64 eggs in group within cottony ovi sac. The average length, breadth, incubation and hatching percentage of eggs were 0.35 ± 0.02 mm, 0.20 ± 0.01 mm, 42.32 ± 8.41 minutes and 84.66 ± 11.05%, respectively. The average total nymphal periods of male and female were 19.8 ± 1.54 days and 21.28 ± 2.29 days, respectively. Adult male was delicate, slender, elongate and smoky brown with a single pair of wings, measured 1.18 ± 0.06 mm in length with wing expansion of 2.33 ± 0.06 mm. While female adult was elongate oval, flattened dorso-ventrally and measured 2.23 ± 0.26 mm in length and 0.87 ± 0.07 mm in breadth. The longevity of the male and female adult was 2.6 ± 0.59 and 28.8 ± 2.60 days, respectively. The pre-oviposition, oviposition and post-oviposition periods recorded 8.1 ± 1.44, 13.26 ± 2.40 and 4.43 ± 3.03 days, respectively. The sex ratio of male to female was 1 1.72. The total life span of both male and female from egg stage to death of an adult averaged 22.4 ± 1.63 and 50.06 ± 3.12 days, respectively. The highest population of mealybugs per plant were found in first fortnight of November (93.68) and showed significant positive correlation with maximum temperature and negative significant correlation with average relative humidity. Under field condition, the nymphs and adult females were preyed upon by two predators Spalgis epius (Westwood) and Scymnus coccivora (Aiyar).

Key words : Biology, Phenacoccus solenopsis Tinsley, Hibiscus rosa-sinensis L. Population dynamics