7 pp.

No description available.

Cassava mosaic disease (CMD) is caused by whitefly-transmitted geminiviruses and is a major constraint to cassava production in Africa. Field surveys were conducted in three (Bushbuckridge, Mariti and Tonga) cassava growing areas of Limpopo and Mpumalanga provinces in South Africa during two seasons (2004/2005 and 2005/2006). Results showed that a higher percentage (27.1%) of CMD infection was due to the use of infected planting materials compared to whitefly borne-infections (10.4%). Disease symptoms were generally mild. There was no change in disease incidence over the survey period. Molecular characterization of cassava mosaic geminiviruses (CMG’s), using differential primer PCR, restriction fragment length polymorphisms (RFLP’s), phylogenetic and recombination analysis and screening for satellite DNA’s. Differential primer PCR and RFLP’s showed that African cassava mosaic virus (ACMV) was the most prevalent virus in South Africa and that mixed infections were a common occurrence. Phylogenetic analysis and RFLP’s showed the presence of a ‘new’ strain of ACMV in South Africa. EACMV isolates from this study showed more frequent recombination compared to ACMV isolates. None of the samples tested positive for satellite DNA’s. Phylogenetic analysis of Bemisia tabaci using the mitochondrial cytochrome oxidase gene sequences revealed a ‘new’ sister clade of B. tabaci that is closely related to the previously identified southern African clade and the presence of the Q biotype that groups with Q biotypes of North African/Mediterranean origin. Good cultural practices, introduction of resistant cultivars and continuous monitoring are required to reduce the impact of CMD in South Africa.

Thesis (Ph.D.). / Written for the Dept. of Natural Resource Sciences, Macdonald College of McGill University. Title from title page of PDF (viewed 2008/08/04). Includes bibliographical references.

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

No description available.

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

4 pp. / This bulletin will provide a comprehensive update of the statewide guidelines for whitefly management in cotton (Last version, 4/96), including guidelines for crop and host management, scouting and decision-making, areawide impact, and effective chemical use. A new set of resistance management guidelines will be highlighted.

No description available.

Physiological factors that might influence ecological dynamics were investigated to better explain the biology of Bemisia tabaci in the desert southwest. Trehalulose, a unique disaccharide only found in unusually large quantities in B. tabaci honeydew, was shown not to be different from sucrose in promoting longevity in honeydew-consuming parasitoids, indicating this insect-modified sugar does not affect the nutritional quality of aleyrodid excreta. Trehalulose is not believed to function as a feeding deterrent to natural enemies. Experiments were designed to examine the effect of temperature on sorbitol and trehalulose production by the whitefly. High performance liquid chromatography analysis of honeydew and whole body extractions revealed a negative relationship between amounts of trehalulose in the honeydew and sorbitol accumulation in the whitefly body, linking these two molecules as important to the nutritional ecology of whiteflies. In another experiment to better understand the dispersal of whiteflies across the landscape, studies of flight over multiple days were conducted to describe the role of prior flight experience on dispersal and migratory flight. Flight performance traits were measured over multiple days of flight to compare two groups of B. tabaci, those trapped moving outside of planted fields with those collected within fields. Trap-caught individuals exhibited flights of significantly shorter duration in a vertical flight chamber. Flights determined to have characteristics of migratory behaviors were initially of longer duration for trap-captured whiteflies than their field-collected counterparts. Over the context of multiple days, however, their longer flights were followed by much shorter flights on subsequent days. Although many insects from both groups were capable of movement on multiple days, almost all of these flights were of a foraging nature. Foraging flights of short duration would likely not add to dispersal distances, thereby limiting whiteflies to their originating patch.