Effect of environmental conditions (temperature and precipitation) on severity of guava die-back caused by Colletotrichum spp. under climatic conditions of Pakistan

Guava cultivation is swiftly rising in the progressive farming community because of its early bearing pattern and long harvesting duration. Despite a 20–25% expansion in the area under guava cultivation in the last decade, the yield has not significantly increased accordingly. However, its production decreased approximately 15% due to the guava die-back, which is quite alarming. The present study was designed to assess guava die-back in three provinces (Punjab, Khyber Pakhtunkhwa and Sindh) of Pakistan and to elucidate the actual pathogen responsible for it. The current study results based on two year data (2017 and 2018) shows a significantly varying level of disease incidence and severity in different guava-producing regions. The cluster analyses display that 46 locations of 18 districts, which designate for higher or lower disease intensity, were clustered in a particular group suggests that particular environment influences the intensity of the die-back severity. The weather factors, i.e., temperature and precipitation results, show if the temperature exceeds 35 °C, the disease severity decrease revealed that optimum temperature (24–27 °C) is needed for the survival of Colletotrichum spp. while high precipitation enhances disease development. Pathogen morphology and pathogenicity assay confirms that Colletotrichum spp. are involved in causing the guava die-back. Thus, the current investigation is significantly helpful to estimate the persistence level of die-back disease in guava orchards as well as it also develops an understanding about pathogen behaviour in conducive environmental conditions.