title: Thermal Time Model for Egyptian Broomrape (Phelipanche aegyptiaca) Parasitism Dynamics in Carrot (Daucus carotaL.): Field Validation.
abstract: Carrot, a highly profitable crop in Israel, is severely damaged byPhelipanche aegyptiacaparasitism. Herbicides can effectively control the parasite and prevent damage, but for optimal results, knowledge about the soil-subsurface phenological stage of the parasite is essential. Parasitism dynamics models have been successfully developed for the parasitesP. aegyptiaca, Orobanche cumana, andOrobanche minorin the summer crops, tomato, sunflower, and red clover, respectively. However, these models, which are based on a linear relationship between thermal time and the parasitism dynamics, may not necessarily be directly applicable to theP. aegyptiaca-carrot system. The objective of the current study was to develop a thermal time model to predict the effect ofP. aegyptiacaparasitism dynamics on carrot growth. For development and validation of the models, data was collected from a temperature-controlled growth experiment and from 13 plots naturally infested withP. aegyptiacain commercial carrot fields. Our results revealed thatP. aegyptiacadevelopment is related to soil temperature. Moreover, unlikeP. aegyptiacaparasitism in sunflower and tomato, which could be predicted both a linear model,P. aegyptiacaparasitism dynamics on carrot roots required a nonlinear model, due to the wider range of growth temperatures of both the carrot and the parasite. Hence, two different nonlinear models were developed for optimizing the prediction ofP. aegyptiacaparasitism dynamics. Both models, a beta function model and combined model composed of a beta function and a sigmoid curve, were able to predict firstP. aegyptiacaattachment. However, overallP. aegyptiacadynamics was described more accurately by the combined model (RMSE = 14.58 and 10.79, respectively). The results of this study will complement previous studies onP. aegyptiacamanagement by herbicides to facilitate optimal carrot growth and handling in fields infested withP. aegyptiaca.
authors.affiliation: Department of Phytopathology and Weed Research, Newe Ya'ar Research Center, Agricultural Research OrganizationRamat Yishay, Israel; R. H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food and Environmental Sciences, The Hebrew University of JerusalemRehovot, Israel.
authors.forename: Amnon
authors.initials: A
authors.lastname: Cochavi
authors.affiliation: R. H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agricultural, Food and Environmental Sciences, The Hebrew University of Jerusalem Rehovot, Israel.
authors.forename: Baruch
authors.initials: B
authors.lastname: Rubin
authors.affiliation: Department of Phytopathology and Weed Research, Newe Ya'ar Research Center, Agricultural Research Organization Ramat Yishay, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Achdari
authors.affiliation: Department of Phytopathology and Weed Research, Newe Ya'ar Research Center, Agricultural Research Organization Ramat Yishay, Israel.
authors.forename: Hanan
authors.initials: H
authors.lastname: Eizenberg
keywords: beta function; broomrape; cross validation; growing degree days model; sigmoid curve