Temporal progress of coffee leaf rust and environmental conditions affecting severity in Veracruz State, Mexico

Abstract

Coffee is an important crop in Mexico. Unfortunately, coffee production has been affected by coffee leaf rust (CLR). For Veracruz, the second state in Mexico with the major production of coffee, there are available reports of weekly CLR severity, but these are only informative without in-depth inferential analysis. We analyzed variations of CLR severity along the year in Veracruz with data from municipal weekly reports provided by Mexico’s federal government phytosanitary epidemiological monitoring coffee program. We selected reports dated in 2018 from nine municipalities and after calculations of mean monthly severity values, we conducted a one-way ANOVA (months as factors) of severity data. We compared this information with other coffee-producing regions. Additionally, we explored the association of temperature, rainfall, and altitude with CLR severity using Principal Component Analysis and multiple linear regressions. Temperature and rainfall data were obtained from Mexican National Meteorological Service. We found that CLR severity in October, November, December, and January (months of harvest period) was significantly higher than values from March-June. During the harvest period, coffee plants allocate resources mainly for fruiting which competes in resources for other tasks such as defense and leaf growth, so this competition of resources can explain the positive relationship found between fruit load and CLR severity. This monthly variation of severity was similar to those reported in Chiapas, Guatemala, Colombia, Uganda, and Ethiopia. Our model (R2 = 0.948) showed a significant and negative effect of minimum and maximum temperature (in a range from 9.9 – 15.5 °C and 18.5 – 26.5 °C, respectively) on CLR severity, while the effect of rainfall (in a range from 32.0 – 359.9 mm) and médium temperature (from 14.3 – 20.5 °C) was positive. With our study, we suggest applications of fungicides in March-June when coffee plantations are in leaf phenophase.