Weather-Monitoring Instrumentation 



for Plant Disease 



Management Programs and 



Epidemiological Studies 



by 

 W. E. MacHardy and J. Sondej* 



INTRODUCTION 



The instrumentation described in this bulletin has been devel- 

 oped to sense and record weather data required for epidemiological 

 studies and disease management programs of apples and potatoes. 

 However, the adaptability of this instrumentation and the data it 

 provides allow it to be used with a wide range of crops, diseases, and 

 management programs. The instrumentation has several features 

 considered essential for the programs being developed: low-cost, 

 low-maintenance, limited-servicing, simplified design and technol- 

 ogy, easy-calibration, battery-operation, durability, reliability, and 

 flexibility (adaptability to orchard and field crop conditions). The 

 following environmental variables can be monitored and recorded: 



1. temperature (°F or °C) 



2. relative humidity (%) 



3. leaf wetness (hrs.) 



4. rainfall (0.25 mm) 



5. rain intensity (occurrence of each 0.25 mm of rain) 



An important feature is a visual record of the temperature, relative 

 humidity, duration of leaf wetness, and rainfall intensity aligned on 

 one chart. This allows a person to immediately examine, compare, 

 and assess these variables in the field, either individually or as they 

 interrelate. 



Two instrumentation designs are described. Each design records 

 the same weather data (Fig. 1), and each utilizes a standard two-pen 

 arm hygrothermograph as the main component. In addition, each 

 design includes a digital rain gauge (a^, a2, Fig. 2) and a device for 

 indicating the hours of leaf surface wetness (b. Fig. 2), both of which 

 are linked electronically to pen arms on the hygrothermograph (c. 

 Fig. 2). The major distinction between the two designs is that one 

 requires modification of a hygrothermograph to accommodate two 

 additional pen arms (Fig. 1-A) while the other requires only one 



*A8Sociate Professor of Plant Pathology and Integrated Pest Management Techni- 

 cian, Department of Botany and Plant Pathology, respectively. 



