Mopane (Colophospermum mopane) woodlands are a source of valuable resources that contribute substantially to rural economies and nutrition across Southern Africa. However, a number of factors such as over-harvesting and climate change have brought the sustainability of the mopane woodland resources into question. Insect defoliation remains a major factor contributing to the depletion of woodland resources in rural areas resulting in low vitality and productivity of the woodland. Conventional methods (e.g. visual evaluation) have been used in monitoring insect defoliated areas in the past. These methods are costly and timeconsuming, because of the need to collect data immediately before and after an extreme event. In this regard, remote sensing techniques offer a practical and economical means of quantifying woodland degradation over large areas. Remote sensing is capable of providing rapid, relatively inexpensive, and near-real-time data that could be used for monitoring insect defoliation especially in semi-arid areas where data collection may be difficult. The present study advocates the development of techniques based on remotely sensed data to detect and map defoliation levels in Mopane woodland. The first part of the study provides an overview of remote sensing of insect defoliation, the implications for detecting and mapping defoliation levels as well as the challenges and need for further research especially within Mopane woodland. Secondly, the study explored whether Mopane species can be discriminated from each of its co-existing species using remote sensing. This was done as a prerequisite for classifying defoliation on mopane trees. Results showed that, with limited training samples, especially in semi-arid areas, Mopane trees can be reliably discriminated from its co-existing species using machine learning algorithms and multispectral sensors with strategic bands located in sensors such as RapidEye. These positive results prompted the need to test the use of ground based hyperspectral data and machine learning algorithm in identifying key spectral bands to discriminate different levels of insect defoliation. Results showed that the random forest algorithm (RF) simplified the process and provided the best overall accuracies by identifying eight spectral wavelengths, seven of which belongs to the red-edge region of electromagnetic spectrum. Furthermore, we tested the importance of the red-edge region of a relatively cheaper RapidEye imagery in discriminating the different levels of insect defoliation. Results showed that the red-edge region played an important role in mapping defoliation levels within Mopane woodland with NDVI-RE performing better than the traditional NDVI. Thirdly, the study tested the reliability and strength of the internal validation technique of RF in classifying different defoliation levels. It was observed that the bootstrapping internal estimate of accuracy in RF was able to provide relatively lower error rates (0.2319) for classifying a small dataset as compared to other validation techniques used in this study. Moreover, it was observed that the errors produced by the internal validation methods of RF algorithm was relatively stable based on the confidence intervals obtained compared to other validation techniques. Finally, in order to evaluate the effects of insect defoliation on the biophysical properties of mopane canopies at different defoliation levels, the study estimated leaf area index (LAI) of different defoliation levels based on simulated data. This was done using PROSAILH radiative transfer model inverted with canopy spectral reflectance extracted from RapidEyeRapidEye imagery by means of a look-up-table (LUT). It was observed that the significant differences exist between the defoliation levels signifying reduction in the LAI as a result of the defoliation. Furthermore, results showed that the estimated LAI was in the range of those reported in literature. The NDVI-RE index was the most strongly correlated with the estimated LAI as compared to other variables (RapidEye bands and NDVI). Overall, the study demonstrated the potential of remote sensing techniques in discriminating the state of Mopane woodland after insect defoliation. The results are important for establishing an integrated strategy for managing defoliation processes within Mopane veldt, thereby satisfying both the needs of local populations for Mopane trees and the worms. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

The limited availability of land to forestry and the ensuing emphasis on intensive silviculture, developed a renewed interest in soil pests in the establishment of plantations. Ten field trials were planted over three seasons to determine the mortality factors influencing the establishment of commercial eucalypt and black wattle plantations in the Natal Midlands, and simultaneously, to investigate the chemical control of the soil pest component. A complex of indigenous soil pests contribute to an average 22,9 % failure of Acacia mearnsii and Eucalyptus grandis seedlings from reaching full establishment. This pest complex, which includes termites, whitegrubs, cutworms, tipulid larvae, wireworms, millipedes and nematodes, was responsible for an average 12,3 % of the failure of the plantings to establish. In the absence of termites, in shallow humic soils, whitegrubs followed by cutworms were the most frequent and economically important pests. Eucalypts are more susceptible than wattle seedlings to whitegrub damage when planted in marginal sites. Seedlings in the summer rainfall region were most susceptible to whitegrub damage from December to April; and to cutworm damage during the first two months after planting. An average of 398 hectares was annually damaged by whitegrubs and cutworms. The total annual loss in planting costs and the additional costs of blanking over the three year study period were 1,22 and 2,65 million rands respectively. Existing non-chemical control applicable to woodlot forestry is reported. Chemical control as one of the options in the management of whitegrubs and cutworms was evaluated. The controlled release formulations of carbosulfan 10% and chlorpyrifos 10% at 1,0 g active ingredient/tree (a.i./tree), gamma BRC 0,6% dust at 0,06 g a.i./tree and the synthetic pyrethroid deltamethrin 5 % SC at 0,025 g a.i./tree were persistent and effective in controlling whitegrubs, even when applied early in the planting season. Deltamethrin 5 % SC at 0,025 g a.i./tree was also successful in controlling cutworms. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

Glucose was present in substantially greater concentrations in whole body extracts of fourth instar Aedes aegypti L. larvae than was trehalose; in contrast, trehalose was more abundant than glucose in haemolymph extracts. Preliminary studies suggested that infection of Ae. aegypti by the entomopathogenic digenean Plagiorchis elegans Rudolphi alters the carbohydrate metabolism of fourth instar larvae. Within 24 hours of cercarial penetration, total body extracts of infected fourth instar larvae exhibited decreased trehalase activity, increased trehalose-6-phosphatase activity, and an accumulation of trehalose in comparison to uninfected larvae. Concentrations of glucose, glycogen and lipids, and the activity of glycogen phosphorylase a were similar in extracts of infected and control larvae. The predominant fatty acids, in both control and infected larvae, were C 18:0, C 18:1 and C 18:3. There were no significant differences in the types and proportions of fatty acids found in control and infected larvae. Parasitic infection is discussed in terms of impaired trehalose metabolism.

This project investigated the impact of bird predation on insect pest populations within two cornfields of Southwestern Quebec. Birds were excluded from portions of these fields through the use of bird-proof netting. Rhopalosiphum maidis, Ostrinia nubilalis, Agrotis spp. and Sphenophorus spp. were all found at greater densities in plots where birds were excluded as compared with the non covered plots. Only the adult Diabrotica longicornis population was not reduced by birds. Results significantly suggest that birds can reduce insect pest populations. Bird visits in cornfields with respect to distance from field edge, type of edge habitat and corn phenology were also studied. Red-winged Blackbird, Song and Chipping Sparrows and American Robin were the most frequently observed bird species inside cornfields. Early in the summer, birds tended to stay closer to the field edge, especially when composed of mature coniferous trees. Different bird species visited the cornfields at specific periods during corn development.

Title page, contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / Brassica vegetables and oilseeds are economically important crops worldwide. These crops are associated with several destructive and widespread insect pests. In Australia these pests include six species, Plutella xylostella (Linnaeus), Pieris rapae (Linnaeus), Hellula hydralis Guenée, Helicoverpa punctigera (Wallengren), Brevicoryne brassicae (Linnaeus) and Myzus persicae (Sulzer), which are the focus of this research. Among them P. xylostella (diamondback moth or DBM) is the most serious and destructive insect pest. Little is known about the potential of predators, which may be able to contribute to control diamondback moth, although some field studies have shown the overall importance of predators in controlling this key pest. The aim of this study was to develop a method that allows study of predator-prey trophic interactions in the field. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1294814 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007

Title page, contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / Brassica vegetables and oilseeds are economically important crops worldwide. These crops are associated with several destructive and widespread insect pests. In Australia these pests include six species, Plutella xylostella (Linnaeus), Pieris rapae (Linnaeus), Hellula hydralis Guenée, Helicoverpa punctigera (Wallengren), Brevicoryne brassicae (Linnaeus) and Myzus persicae (Sulzer), which are the focus of this research. Among them P. xylostella (diamondback moth or DBM) is the most serious and destructive insect pest. Little is known about the potential of predators, which may be able to contribute to control diamondback moth, although some field studies have shown the overall importance of predators in controlling this key pest. The aim of this study was to develop a method that allows study of predator-prey trophic interactions in the field. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1294814 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2007

Thesis (M.A.)--Texas State University-San Marcos, 2007. / Vita. Appendices: leaves 52-78. Includes bibliographical references (leaves 79-83).

Thesis (M.A.)--Texas State University-San Marcos, 2007. / Vita. Appendices: leaves 52-78. Includes bibliographical references (leaves 79-83).

Thesis (M.S.) -- Mississippi State University. Department of Entomology and Plant Pathology. / Title from title screen. Includes bibliographical references.

Thesis (M.Inst.Agrar.(Entomology ))--University of Pretoria, 2003. / Includes abstract in English. Includes bibliographical references.