Factors Influencing Phytophthora infestans Mont. de Bary Attack Degree in Potato

The strong relationship between the late blight and climatic factors (namely temperature and rainfall)  has  important  consequences  on  potato  crops.  In  Romania,  in  early  spring  and  early  fall  the attack  degree  of  the  Phytophthora infestans  Mont.  de  Bary,  late  blight  pathogen,  is  low  because  in European  climate  average  temperature  is  not  more  than  10 0C,  and  usually  the  rainfall  supply  is reduced;  it  increases  in  late  spring  and  summer  when  average  temperatures  are  around  20 0C  and rainfall average more that 65 mm/month. The aim of this paper is to describe the relationship between temperature, rainfall regimen and late blight attack degree in potato cultures. The research was carried on  during  two  years,  2009  and  2010,  in  three  experimental  fields  from  Transylvania:  Răhău,  Alba; Maieru,  BistriÅ£a-Năsăud;  Draguș,  Brașov.  Classical  methodology  was  used  for  monitoring.  The  data were statistically processed using STATISTICA  v. 7.0 programme. The interrelation attack degree - abiotic  factors  reflects  a  maximum  intensity  of  the Phytophthora infestans  Mont.  de  Bary  attack degree by the entire year 2009 around 42 % recorded when the rainfall average values begin with 110 mm  and  thermic  conditions  correspondent  to  values  bigger  than  20 0C.  In  the  year  2010  the multiregression  analyze  of  the  monitored  interactions,  led  to  a  very  strong  multiple  correlation coefficient  of  0.938  representative  in  share  of  87.90%.  In  2010,  by  the  entire  monitored  period,  the rainfall supply had a bigger influence on the attack degree compared to thermic conditions. In 2009, the predicted biggest recorded attack degree of Phytophthora infestans de Bary was of 44% while in 2010 it was of 40 %, correspondent to rainfall and temperature regimens.