Thesis - University of Michigan. / Reprinted from the American naturalist, vol. LXXX, no. 794 ... September-October, 1946. Literature cited: p. 546.

The greenhouse whitefly (Trialeurodes vaporariorum) is one of the most destructive pests of greenhouse tomato (Lycopersicon esculentum) crops. The success of biological or insecticidal control of whiteflies has never been complete. Attention has therefore been directed recently to the possibility of developing tomato cultivars resistant to whiteflies. Whiteflies were caged on leaflets of ten tomato cultivars, two of the woolly mutant lines and four other species of Lycopersicon to observe the effect of host plants within this genus on fecundity and longevity of the insects. The results showed wide variation among hosts. Significant negative correlations were revealed between the mean density of glandular hairs on the upper foliar surface of different cultivars and means for the fecundity of whiteflies caged on these cultivars. A high level of resistance to whitefly, not related to density of glandular hairs, was observed in plants that were either Van Wert's woolly mutant or L. peruvianum var. humifusum. Resistance of the former seemed to be related to a high density of branched non-glandular trichornes whereas that of the latter was not morphologically apparent. There were indications of both antibiosis and nonpreference operating in the humifusum. Further experimentation revealed a high nymphal mortality for whiteflies developing on plants of this line, reduced fecundity of adults which had developed on the humifusum, and a preponderance of male progeny from adult insects which had lived exclusively on these plants. It was concluded that the resistance of L, peruvianum var. humifusum to whitefly is sufficient to justify its use in a breeding program to develop greenhouse tomato cultivars resistant to this pest. / Land and Food Systems, Faculty of / Graduate

No description available.

Diploma Thesis concerns with usage of entomopathogenic fungi in system of biological control against greenhouse whitefly Trialeurodoes vaporariorum and sweetpotato whitefly Bemisia tabaci. The Aim of diploma thesis was through in vivo and in vitro experiments determinated the basic evolutional and vegetative characteristics of selected entomopathogenic fungi and compare their effectivity in completed system {\clqq}plant - pest - pathogenic``. All experiments and results are demonstrated in the tables and the graphs. The photo-documentation of the method used during founding and interpretation of experiments is the part of the thesis.

The use of entomopathogenic fungi to control agriculturally important pests, both in greenhouses and in the field, has been demonstrated by various authors for a number of years. This has been brought about by the development of resistance in certain pest species to chemical applications and a growing public awareness of the safety implications of residual insecticides. Several entomopathogenic fungi were tested against four insect pests found in the Republic of South Africa (RSA), the greenhouse whitefly, Trialeurodes vaporariorum, the rice weevil, Sitophilus oryzae, the grapevine mealybug, Planococcusficus and the sugarcane stem borer, Eldana saccharina. Further concentration, temperature and humidity studies were conducted with selected isolates on the rice weevil, S. oryzae. Sitophilus oryzae is considered one ofthe most important pests of stored grain. Several fungal isolates were tested against the rice weevil, four of which, B1, PPRI 6690, PPRI 6864 and PPRI 7067, were selected for further testing based on the mortality results over a 21 d period. Varying conidial concentrations were applied and at high doses of 1x10 -6 conidia ml -1 with mortality rates of to 84% achieved. LT 50 values ranged from 6 - 68d. Increased spore concentration resulted in an increase in overall mortality. Temperature and humidity was found to affect the infection potential of the four isolates tested. Four temperatures ranging from 15 - 30°C were tested. The highest mortality rates were obtained at 25°C where mortality ranged from 46 - 65% in 14d. Mortality rates decreased with decreasing temperature, and no mortality was recorded at 30°C. Temperature was found to significantly alter the LT 50 values, increasing the LT 50 with decreasing temperatures. Decreasing the humidity resulted in an increased LT 50 and a reduction in the overall mortality rates. The mortality of S. oryzae ranged according to the RH and isolate. Isolates Bland PPRI 6690 resulted in the highest mortalities of 80 and 83% at 92.5% RH, with LT 50's of 6.3d and 6.4d, respectively. Several entomopathogenic fungi were tested against T vaporariorum, P. ficus and E. saccharina, three key pests of South African crops. Nine fungal isolates were tested against the greenhouse whitefly, T vaporariorum, with mortalities ranging from 26.7 - 74.7% over 14d. Beauveria bassiana Isolates Bl and PPRl 6690 produced the highest mortality rates and were recommended for further pathogenicity testing against T. vaporariorum. Planococcus ficus is a common pest ofvineyards in the Western Cape Province, South Africa. Nine entomopathogenic fungi were screened against P.ficus, only two of which produced mortality. Eldana saccharina is a stalk borer, which infests sugarcane in large areas of Southern Africa. Five isolates were tested against second and third instar larvae, three of which, B1, PPRl 6864 and PPRl 6690 resulted in mortalities. Mean percentage mortality was low for all three isolates. From the study it was evident that two of the isolates tested, Bland PPRI 6690 (B. bassiana), showed potential against three of the four pests, and two isolates of Lecanicillium lecanii caused mortality in P. ficus. Further research and understanding of the effect of environmental conditions, spore concentration and epizootic potential would result in the further development of these isolates as future biological control agents. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.