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Subject: Agricultural Entomology × Author: KAU × End date: 1993 × Start date: 1993 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Mass trapping of the sweet potato weevil (Coleoptera: Curculionidae) males using sex pheromone
    (Department of Agricultural Entomology, College of Horticulture,Vellanikkara, 1993) Mini, E S; KAU; Sitarama Rao, S
    The efficacy of the synthetic pheromone of C. formicarius elegantulus in attracting the males of C. formicarius formicarius was tested in the field. The effect of continuous mass trapping of adult males on the population build up of the pest in the field was assessed. The effect of different doses of pheromone as influenced by the trap designs was also assessed. Low cost traps designed and fabricated out of locally available materials were tested in the field and incremental benefit of treatments was worked out. The range of attraction of pheromone doses was assessed by analysing the recapture data of marked males released at different distances from the pheromone baited traps. The results indicated that the weevils were most active during the night as is evidenced by higher capture of weevils at morning observations than those in the evening observations. The weevil catch was not significantly influenced by the higher doses of pheromone. Day light affected the flight pattern of weevils while the moon phases have no significant effect. continued attraction of males towards the pheromone baited traps indicated their effectiveness inspite of the presence of virgin females in the field. The pheromone doses were effective in checking the rapid build up of the pest in the field as evidenced by the non reduction in vine weight. Among the three trap designs polythene bag trap was the cheapest one to install and resulted in the most favourable C : B ratio. The attraction of the pheromone doses decreased with increase in the distance of release from the pheromone source. A distance of 25 m was found to be ideal for placement of traps in the field. The cheapness of traps facilitate installation of large number of traps at reasonable increase in cost.
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    ThesisItemOpen Access
    Impact of insecticides on the flora and fauna in the soil ecosystem of banana plantation
    (Department of Agricultural Entomology, College of Agriculture, Vellayani, 1993) Alice Renta Packia Sujeeth, J; KAU; Mammen, K V
    Possible adverse effects of the insectisides recommended for the control of pests/diseases of banana in Kerala, on the useful soil organisms and the consequent impact on the banana ecosystem were studied in detail through a field experiment and follow up laboratory investigations. The results revealed: (1) Earthworm population was adversely affected with HCH even in low doses upto two months after the treatment. With carbofuran soon after the first and second application the population declined but restored with in two months. In the case of phorate the first treatment alone caused significant adverse effect while the second and third did not cause any significant effect on the earthworms. Even in carbofuran and phorate treatments earthworms. Even in carbofuran and phorate treatments earthworm population came on par with control two months before the harvest. (2) Parasitic nematodes were unaffected by HCH treatment. With carbofuran significant reduction in the population of parasitic nematode was noted after two applications of the insecticide. The nematicidal effect was seen lost throughout the period of observations from the eighth month. In phorate treatment significant reduction was observed only after three consecutive applications of the toxicant. The overall reduction caused by phorate was not adequate. Carbofuran was hence better to control parasitic nematodes than phorate. In both the cause the low level of nematode population in soil may be attributed to the lack of response to the nematicides recommended for the control of the pest. (3) HCH treatment was not at all toxic to non-parasitic nematodes. In the case of carbofuran and phorate low population was observed throughout, while significant reduction was observed for a short while after the first application of the insecticides only. (4) Collembolan and mite population was not reduced by HCH treatment. Significant reduction was observed for two months after the first and second applications of carbofuran and phorate. Adverse effect was then lost and the population was maintained on par with control till harvest. (5) The bacterial count was low throughout in HCH treatment. Though the carbofuran reduced the bacterial population it was revived in two months time. Phorate suppressed the bacterial population after first two applications, while with the third application slight enhancement was observed on the population and it was restored on par with control before harvest of the crop. (6) In fourth and eighth month a suppressing effect of HCH on actimycetes was noted and a stimulatory effect was observed during the sixth month. In carbofuran no significant reduction was observed upto three months and later on no reduction was noted. In phorate significant reduction was observed after the first and second application and the actinomycets population was then restored and remained unaffected till harvest. (7) Significant reduction of fungi was observed during the third and fourth months after planting in HCH treatment. In carbofuran slight reduction was noted after first and second application. The population was then restored. In phorate slight reduction was noted after two applications and it was restored in the next month itself. The third application showed stimulatory effect and the population was higher than that observed in control in subsequent observations. (8) The organic matter content in treatments and control remained on par and hence the humification process in banana ecosystem, through the activity of the soil organisms, was not seen affected by the application of insecticides. The variations in pH and moisture content of a soil in control plots and treatments also were not statistically significant. (9) Changes in the correlation of soil parameters with the beneficial organisms in control and treatments also did not show any definite trend. This may be due to low variability in the data on the population levels as well as the soil parameters. In general the treatments did not alter the population of the soil fauna and flora in the ecosystem to cause any adverse persistent effect.