|ANWAR, M. - North Carolina Agricultural And Technical State University|
|Larkin, Robert - Bob|
Submitted to: Journal of Plant Protection Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2015
Publication Date: 3/17/2016
Citation: Olanya, O.M., Anwar, M., He, Z., Larkin, R.P., Honeycutt, C.W. 2016. Survival potential of Phytophthora infestans in relation to environmental factors and late blight occurrence. Journal of Plant Protection Research. 56:73-81.
Interpretive Summary: Assessment of pathogen survival may enhance effective management of potato diseases. We utilized a non-parametric density estimation approach and applied a cox regression model to determine the effects of temperature (Temp) and relative humidity (RH) on late blight risks and sporangia survival probability using field data (2005-2006) from a potato production site at Presque Isle, Maine. The distribution of temperature and relative humidity were quantified and found to be favorable for late blight outbreaks and were similar among the years investigated. Disease outbreaks and risk periods coincided with sporangia survival probability (15-35%). The Survival data (cox proportional model) indicated that RH and Temp were significant factors in sporangia survival in comparison to solar radiation. The hazard ratio, which indicates survival risk of sporangia varied with the predictors. Pathogen survival curves and sporangia hazard probabilities may be utilized to complement short-term disease forecasts and enhance late blight management in potato production fields, by using management practices during periods of high risk and pathogen survival.
Technical Abstract: Potato is an important crop globally and late blight (Phytophthora infestans) often results in severe crop loss. The cost for late blight control can be in excess of $210 million in the United States. We utilized a non-parametric density distribution analysis of local temperature (Temp) and relative humidity (RH) from 2005 to 2009 to assess and validate sporangia survival potential using the SUROPY model and late blight risks during potato cropping season at Presque Isle, northern Maine, USA. Model based analyses showed that ambient Temp of 3-30 degrees C and RH values of 45-100% were conducive for sporangia survival. Disease outbreaks and risk periods coincided with high sporangia survival probability (15-35%). Due to over-estimation of survival potential and omission of solar radiation (SR) by SUROPY, we applied a Cox proportional model to estimate the probability of sporangia survival [i.e. hazard at a specific time H(t)] as a function of baseline hazard (H0) and influencing parameters and the model is: H(t)=H_0 (t)*exp'(0.067* ET+0.138*Temp+0.083*RH+0.001*SR). The survival model indicated that RH (Beta =.083) and Temp (Beta =.138) were significant (P<0.05) factors in sporangia survival in comparison to SR (Beta =.001). The predictor variables contributed to reduction of survival based on p-values and standard errors. The hazard ratio, indicative of sporangia survival risk varied with the predictors and for unit increase of Temp, sporangia survival hazard increased by 1.148 times. The Cox model and sporangia hazard probabilities can complement short-term disease forecasts and provide improved options for late blight management.