|Authors: ||J. Lorbeer, C.H. Petzoldt, T.W. Walters|
The disease forecast program BLIGHT-ALERT and conventional disease control methods were evaluated in twenty-two side-by-side comparisons in growers' fields in New York for the control of Botrytis leaf blight (BLB) caused by Botrytis squamosa during 1987-93. On average growers made 5.5 fungicide applications using BLIGHT-ALERT and 7.8 fungicide applications using conventional disease control techniques resulting in an average savings of 2.3 applications or about 29%. No differences in yield and quality were observed between the BLIGHT-ALERT and comparison fields.
Demonstrations were continued with 11 and 12 growers during 1994-95 to continue to promote use of BLIGHT-ALERT. Results observed were similar to the earlier demonstrations with savings averaging 1.8 fungicide applications in 1994 and 3.7 applications in 1995. Resistance to BLB (small lesions and no leaf blight) was observed in the onion accession PI 273212 from Poland during 1994-96. PI 357215 from Macedonia and three open pollinated varieties from New York were observed with resistance to BLB during 1995. A. roylei which produces fertile progeny from hybrids with onion also has exhibited resistance to the disease in New York.
In a controlled inoculation and fungicide spray experiment conducted in 1996, the onion varieties Kasmer Red, Wolska, Rawska, and Spartan Banner required half rates of fungicide sprays with chlorothalonil to achieve acceptable control of BLB as compared to other varieties which required the full rate for acceptable control.
Combining varietal resistance, reduced rates of fungicides, and forecasting will result in improved control of BLB and environmental enhancement in onion production fields.
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