The objectives of this project were to 1) determine the variance in weather conditions and resulting occurrence of disease infestations on a site to site basis within a given area ; and 2) to determine the accuracy of the monitoring units.
Data loggers used were the leaf wetness/temperature logger from Spectrum Technologies and the watchdog data logger. Sites selected were based on crop, geographical location and topography. Sites included and their distance from the central site at the OARDC [ ] were: 1) an apple orchard in a low lying area in southern Wayne Co.[5 mi.], 2) a tomato field in an elevated area in southern Wayne Co.[8 mi.], 3) a tomato field in a low lying area in Summit Co.[28 mi], 4) an apple orchard in an elevated area in northern Wayne Co.[16 mi.], and 5) in a vineyard planting on flat terrain at the OARDC Snyder farm in central Wayne Co. While all sites were monitored for leaf wetness and temperature, these last two sites were also monitored for relative humidity and rainfall as well. Data was pulled 1-2 times per week, depending on weather conditions. The computer used for pulling the data was an IBM 755C Thinkpad.
Software and hardware problems during the first part of the summer did not allow for a full season of data collection as intended. Software problems ranged from the program using the wrong date when compiling data, to incompatibility with the IBM Thinkpad. The main hardware problem was rapid depletion of the battery (2-3 days) due to a short in one of the units. Software problems were solved by mid-July.
The unit in the vineyard at the OARDC had a Campbell CR21 monitoring unit within several feet of it, already placed there by Plant Pathology. In comparing the data between the two units from August 16th through October, the daily lows and averages were within one-half degree C of each other. The daily highs were normally within 1 degree C of each other, but varied as much as 3 degrees C on several occasions. Rainfall amounts were also very similar overall, but did vary up to 10 mm on one occasion. The leaf wetness hours varied considerably - as many as 15 hours per day on some days. Though the effort was made to put the Watchdog leaf wetness sensor in a similar canopy as that of the CR21, it is felt that placement caused the difference rather than fault of the unit.
In comparing apple scab infection periods between the two orchards, the Mills scale, having values from 0 (no infection) to 3 (heavy infection), was used. From July 8th through October 10th, 24 infection periods of 1 or greater were recorded in the southern orchard. In the same period of time, only 17 periods were recorded in the northern orchard. Using an infection period of 2 or greater as a threshold and an assumed 7 day period of protection after application, the southern orchard would have required 7 fungicide applications during this period to protect the crop from infection. The northern orchard would have required only 5 fungicide applications. Scab pressure was very low for the season, making evaluation of the crop for disease infestation impractical.
In apples, the data recorder was also used for determining the proper spray date for codling moth control. Biofix dates were determined by trapping and scouting the orchards for the first sustained flight. Degree day (DD) reports were then tracked to determine the proper spray date. For codling moth, this is 250 DD (base 50) after the biofix. The southern orchard had heavy flights of codling moth throughout the summer, and therefore subsequent sprays were applied 200 DD after moths were again found in the traps. By using this method, fruit damage was kept to a minimum. Unsprayed trees in the area sustained heavy fruit damage. The northern orchard had very low infestations of codling moth, and required only one pesticide application for control.
In comparing the tomato fields for early blight, Tom-cast, with a cumulative DSV value of 16 as the threshold, was used. From July 14th through September 2nd the Wayne County location accumulated 62 DSV's and required 4 fungicide applications. During the same period, the Summit County location accumulated 50 DSV's and required 3 fungicide applications. Early blight infestations were light in both plots, with harvest continuing 2-3 weeks longer than normal. However, due to the dry weather, disease pressure was also light even in unsprayed plots.
The data from the tomato plots was also compared to a Campbell CR10 unit based in Fremont. For the period from July 14th through August 22, DSV's accumlated were 65 in Fremont, 43 in Summit Co. and 61 in Wayne County.
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