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A Computer-Controlled Environmental Chamber for the Study of Aerial Fungal Spore Release

First author: U.S. Department of Agriculture, Agricultural Research Service, U.S. Horticultural Research Laboratory, Orlando, FL 32803; second author: DPT 140 Candace Dr., Maitland, FL 32751; and third author: Citrus Research and Education Center, University of Florida, Institute of Food and Agriculture, Lake Alfred 33850

An environmental chamber was designed to study aerial release of spores of ascomycetes and hyphomycetes, based on a device developed by C. M. Leach. Relative humidity (RH), temperature, red (660 nm) and infrared (880 nm) light, leaf wetness, wind speed, vibration, and rain events are controlled and monitored within the chamber via an RTC-HC11 real-time controller and data-acquisition system. A BASIC11 computer program is uploaded to and controls the system. The program requests values for environmental parameters that change through time according to user specifications. The controller interacts with a stepper motor, solenoids, and relay switches via a feedback system based on data received from solid-state RH, temperature, and leaf-wetness sensors. The data-acquisition system records environmental data from the chamber in RAM (random access memory) that can be downloaded to a personal computer for correlation with spore-release data. Spores released from fungal specimens on plant tissues and cultures placed in the chamber and subjected to the desired environmental conditions are collected on a continuous volumetric spore trap at an exhaust port from the chamber. The performance of the device was examined by measuring spore release of Mycosphaerella citri, Alternaria solani, and Venturia inaequalis under various environmental conditions.

Additional keywords: apple scab, citrus greasy spot, early blight of tomato and pepper.