Effect of jassid {(Jacobiasca lybica (de Berg.)}density on number of flowers and leaf-damage as yield components of eggplant at different growth stages

Sampson Akoi Binyason, Z. T. Dabrowski, El-Imam El-Khidir


The effect of different jassid, Jacobiasca lybica (de Berg.) densities on the number of flowers and leaf-damage as yield components of eggplant (Solanum melongena L.) at different growth stages were evaluated in cage experiments at Kenana Research Station, during autumn 1995/96, winter 1995/96 and autumn 1996/97 growing seasons. The objectives were to establish the density-damage relationship, identify the most critical crop growth stage when there is a maximum injury or loss in yield and to determine the lowest pest population which would necessitate control measures. The results demonstrated a direct relationship between leaf damage symptoms and number of flowers and jassid density. As the number of jassids/leaf increased the rate of leaf-damage also increased. On the contrary, the number of flowers/plant decreased with increase in jassid density and rate of damage. However, the relationship varied according to the age of the plant. Younger plants of 30-45 days after sowing (DAS), were more sensitive, those at 60-65 DAS were moderately susceptible and those at 90-95 DAS were tolerant with reduction in number of flowers by 79.8%, 51.8% and 20.0%, respectively. The action threshold also increased with the advancing age of the plants as follows: 0.7, 0.8 and 0.9 jassids/leaf for the 30-45 DAS, 60-65 DAS and 90-95 DAS, respectively.

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