Life Fertility Table of Sorghum Aphid, Me/anaphis sacchari in Laboratory

Life table is a useful technique in the study of population dynamics of an insect population. Survival and fecundity rates are also the two important parameters, which contribute towards aphid population increase. Results of the study indicate that the sorghum aphid, Melanaphis sacchari (Zehntner) (Homoptera: Aphididae) reproduced parthenogenetically from second day in 61581and RSSV 9; from third day on IS 2312 and SSV 84. The survival pattern of sorghum aphid on the selected genotypes showed a stair step type to a slight convex survival ship curve. It was found that survival of the aphid was highest during the second day for the susceptible genotype RSSV 9 and continues so up until the sixth day and declines gradually in the subsequent days.

In the population growth study of the sorghum aphid, the results indicate that the highest net reproductive rate (Ro) was recorded in the susceptible genotype 61581 (3.2) followed by RSLG 262 (2.9) during the generation time of 2.4 and 1.6 days, respectively. In contrast, the lowest net reproductive rate (Ro) were observed in the less susceptible genotypes viz., 61526, Lakadi, Selection 3, Swati and SSV 84 ranging between 1.6 to 1.9. The aphid resistant line 61581 had the highest value (0.276) for capacity to increase than all the genotypes. While, the value being lowest and negligible (0.093) in the aphid resistant line 61526, local cultivars Lakadi, and the national/state varieties Selection 3 and Swati recorded 0.087, 0.095, 0.095, respectively. The instantaneous rate of increase (r), which was obtained from the poptools software as the number of female progeny produced per female per day was much lower in genotypes 61526, SSV 84, M 35-1, C43 and RSE 3.