.. LABORATORY TECHNIQUES Section III INSECT PATHOLOGY MANUAL … pressure cooker or oven, you can use certain chemical agents such … This section describes a number of techniques which will be useful to insect pathologists working in the laboratory. Most of the techniques will be familiar to plant or medical pathologists. The reader is strongly advised to seek advice and assistance from pathologists trained in other fields. The techniques described assume that the pathologist has access to a reasonably well-equipped laboratory, including autoclave or pressure cooker, microscope, glassware, and chemicals. A list of essentail basic equipment and some suggested suppliers is given in Appendix IV. For guidance on the identification of the most common fungi affecting insects, please see Section 2.

12 6. MICROSCOPY After sterile technique, learning to make good use of the microscope is the next technique to be mastered by any pathologist . MICROSCOPES A brief description of types of microscopes and their uses. Dissecting: taxonomy, surface examination of insects, dissecting to reveal internal organs, x10 – x50 magnification, reflected light source (i.e. light from above) Compound: pathogens, x100 – x1,000 magnification, transmitted light (from underneath) Phase contrast: some compound microscopes have a phase contrast condenser which gives greater clarity for examining pathogens at high magnification Electron: emits a beam of electrons instead of a light beam. This is for examining very fine structures. It is an extremely expensive piece of apparatus. Scanning electron microscope (SEM): x100 – x50,000 magnification gives three dimensional images for defining shapes in surface structure Transmission electron microscope (TEM): x10,000 – x1,000,000 magnification only for very thin sections or for isolated pathogens. Specialised equipment is required to prepare these sections. USING A MICROSCOPE 1 Turn on the microscope and check that the light is working. 2 Place a piece of thin tissue on a slide with a coverslip on top. 3 Make sure the lowest power objective is in place. 4 Adjust the eyepieces to a comfortable viewing position. 5 Focus by lowering the objective towards the slide while watching from the side. Then look through the microscope and focus up slowly until the tissue comes into focus. Never focus down towards the slide.

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