Authors
Arne
Stensvand
and
Håvard
Eikemo
,
Norwegian Crop Research Institute, Plant Protection Centre, Department of Plant Pathology, N-1432 Ås, Norway
; and
David M.
Gadoury
and
Robert C.
Seem
,
Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456
ABSTRACT
Estimates of ascospore maturity generated by a model developed previously in New Hampshire, United States, were compared with the cumulative release of ascospores in southern Norway as monitored by volumetric spore traps at one site for 12 years, and at two additional sites for 2 years. In locations and years with frequent rain events, model-estimated ascospore maturity closely approximated observed ascospore release. However, in years with protracted dry periods of 1 to 3 weeks with no or little rain, not only was spore release delayed, but release continued to lag behind predicted maturity even after several rain events subsequent to the dry interval. By halting degree-day (base = 0°C) accumulation if 7 consecutive days without rain occurred, accuracy of the model during “dry” years was greatly improved, without substantially affecting accuracy in “wet” seasons. With minimal additional effort on the part of the user, this simple modification increases the accuracy of model-derived estimates of ascospore maturity when lack of rain slows ascospore maturation.
