Eizenberg, H., Department of Weed Research, Newe Ya'ar Research Center, P.O. Box 1021, Ramat Yishay 30095, Israel
Colquhoun, J., Department of Crop and Soil Science, Crop Science Building 107, Oregon State University, Corvallis, OR 97331, United States
Mallory-Smith, C.A., Department of Crop and Soil Science, Crop Science Building 107, Oregon State University, Corvallis, OR 97331, United States

The root-parasitic broomrape species cause severe damage to field and vegetable crops worldwide. This study evaluated the relationship between small broomrape development and temperature with red clover as a host plant. Red clover plants were grown in soil artificially infested with small broomrape seed in temperature-controlled growth chambers. Parasite development was quantified at 48 different accumulated growing degree days (GDD). Small broomrape parasitism and temperature were strongly related. Small broomrape tubercle initiation was delayed by low temperature. Tubercle development initiated at about 750 GDD and peaked at about 1,100 GDD. Small broomrape biomass accumulation correlated with the increase in tubercle number over time. Parasitism stages were divided into lag, log, and maximum phases that were strongly related to GDD. Development of a predictive system for parasitism growth stage is needed to allow precise herbicide application for effective control before small broomrape shoot emergence.