Can Doppler Radar Precipitation Estimates

Accurately Estimate Rainfall?

Not always. Doppler precipitation estimates do not always compare well with rain gauges measuring precipitation on the ground. However, to use the AUPecan and AUPnut advisories, the radar must distinguish above 0.10 inches or below 0.10 inches. Doppler radar can be used to make this determination efficiently and with reasonable accuracy. For more information, see the abstract below.

Assessment of Doppler Radar-based AU-pnut Leaf Spot Advisory for Use in Georgia.

R. C. KEMERAIT*, G. HOOGENBOOM, R. G. McDANIEL, AND W. A. MILLS, III. Departments of Plant Pathology, University of Georgia, Tifton, GA, 31794; Department of Biological and Agricultural Engineering, University of Georgia, Griffin, GA 30223; University of Georgia Cooperative Extension Service, Waynesboro, GA 30830; and Southwest Georgia Research and Education Center, Attapulgus, GA 31715.

Field trials were conducted to verify the effectiveness of the Doppler radar-based AU-pnut advisory in Georgia and compare rainfall data from ten weather stations (Georgia Automated Environmental Monitoring Network) with Doppler radar estimates. Data was collected from 1 May until 31 Oct 01 and field trials were established at Tifton and Attapulgus with the cv . Georgia Green. A factorial design was used at both sites where main effects were spray schedule (14-d calendar vs. AU-pnut) and fungicide program. Fungicide programs included 1) chlorothalonil, 1.5 pt/A, full season, 2) propiconazole, 2 fl oz/A, +chlorothalonil, 1 pt/A, sprays 1 and 2, azoxystrobin, 18.5 fl oz/, sprays 3 and 5, and chlorothalonil, 1.5 pt/A, sprays 4, 6, and 7; and 3) chlorothalonil, 1.5 pt/A, sprays 1, 2, and 7, and tebuconazole, 7.2 fl oz/A, sprays 3-6. All fungicide applications at Tifton were initiated 35 days after planting (DAP) while the AU-pnut and calendar treatments in Attapulgus were initiated 24 and 34 DAP, respectively. Data from all weather stations and the Doppler radar provided by the Agricultural Weather Information Service, Inc., were in agreement 90.5% of the time as to whether or not a rain event (accumulation >=0.10 in 24 h) had occurred. Doppler radar provided false positive results (rain event predicted but did not occur) 8.8% of the time and false negative results (failed to predict a rain event) 0.7% of the time. At Tifton, all plots received 7 fungicide applications; however, fungicide applications for AU-pnut treatments were generally 3 or 4 days earlier than for the calendar schedule. There was no interaction between spray schedule and fungicide program. There were no differences in leaf spot control, severity of southern stem rot, or yield between the calendar-based and the AU-pnut programs, nor were there differences in leaf spot control or yield across fungicide treatments. There was significantly more southern stem rot in plots that received only chlorothalonil. At Attapulgus, 8 fungicide applications were required for the AU-pnut schedule versus 7 for the calendar program. There was a significant interaction between spray schedule and fungicide program. For fungicide programs that included azoxystrobin or tebuconazole, there were no differences in yield, leaf spot severity, or severity of soilborne disease (Rhizoctonia limb rot + southern stem rot) based upon spray schedule. Where chlorothalonil was used alone, leaf spot control was better when fungicides were applied on the AU-pnut schedule rather than the calendar program. Control of soilborne disease and yields were significantly greater in plots that received azoxystrobin or tebuconazole. Use of a Doppler radar-based AU-pnut leaf spot advisory was an effective tool to manage diseases of peanut without loss of yield in this study. Doppler radar data is not as precise as weather stations in determining rain events; however it appears to be accurate enough to use with AU-pnut.