Theses / Dissertations >
College of Agric and Natural Resources >
Please use this identifier to cite or link to this item:
|Title: ||Biology of cylas spp. on some sweet potato varieties|
|Authors: ||Duku, Emmanuel Boamah|
|Issue Date: ||12-Dec-2001|
|Series/Report no.: ||3295;|
|Abstract: ||Studies were conducted in the field to determine the effect of sowing depths of 2.5 cm, 5cm and 10 cm on Cylas infestation of the sweet potato varieties Sauti, TIS 8266, TIS 84/0320 and TIS 3017 which have been released recently by Crops Research Institute, Fumesua. Other parameters studied included the effect of number of leaves and branches on top 30 cm, vine thickness and internodes length on vine infestation. Investigations were also carried out to determine Cylas species and their population at 2, 3 and 4 months after planting of the sweet potato varieties. At harvest, tuber stalk length of the four varieties was measured and the soluble sugar content, dry matter and latex production were determined. Host preference experiments under no choice and free choice conditions were also investigated.
The level of tuber infestation of the four sweet potato varieties by Cylas spp decreased with increasing depth of planting. - This may explain why sweet potato varieties with long tuber stalk had the least incidence of Cylas. The results also showed that Sauti which had the highest number of leaves and branches, as well as the thickest vine, had the highest incidence of vine infestation. There was an increase in the incidence of the weevil with time on the four sweet potato varieties.
The sweet potato varieties used had varying levels of soluble sugar, percent dry matter content and latex production. It appears that optimal sugar content of sweet potato influences oviposition rate of the weevil which is reflected in the level of Cylas emergence. Higher weevil emergence in TIS 84/0320 may be attributed to its optimal level of soluble sugars present.
There was no significant difference in weevil emergence in the no choice experiment. Significant differences, however, occurred in the free choice experiment. The results show the following order of decreasing magnitude of emergence in the four varieties: TIS 84/0320 >TIS 3017 >Sauti >TIS 8266. There was no varietal influence on the sex ratio of Cylas.|
|Description: ||A thesis submitted to the School of Graduate Studies,
Kwame Nkrumah University of Science and Technology in partial
fulfilment of the requirements for the award of Master of Science, 2001|
|Appears in Collections:||College of Agric and Natural Resources|
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.