Purpose: Stem-end rot (SER) is an endophytic fungal infection of avocado causing significant postharvest losses, affecting its marketability. This study was conducted to identify effective concentrations of selected eco-friendly essential oils and chemicals to control SER pathogens by conducting in vitro bioassays and to develop treatments to control SER in naturally infected avocado (cv. Pollock) using less hazardous alternatives to synthetic fungicides. Research Method:In vitro disc volatilization and poison food bioassays were conducted to identify inhibitory concentrations of some essential oils and chemicals against SER pathogens. Avocado fruits were subjected to eco-friendly fumigation and dip treatments and their pathological, physicochemical and sensory properties were assessed after 7 days of storage at 15 °C. Findings: Disc volatilization bioassay revealed that 5 µL/plate clove oil was most effective againstLasiodiplodia theobromae, Diaporthe nelumbonis and Fusarium oxysporum. According to Poisoned food bioassay, 5% (w/v) sodium bicarbonate and 0.07% (v/v) acetic acid were highly effective against the test pathogens. SER incidence of avocado fruits has been successfully delayed for 7 days after subjecting to fumigation treatment with clove oil and dip treatments with sodium bicarbonate and acetic acid, followed by storage at 15 °C. None of the treatments adversely affected physicochemical and sensory properties of avocado.Originality/Value: Treatments could be further improved by conducting a medium-scale in vivo trial to obtain good quality avocado with higher consumer acceptance.

Avocado (Persia americana) is one of the most popular fruits grown in Sri Lanka. Postharvest infections occur wherever the crops are cultivated. Among them, stem-end rot (SER) is the major disease reported. Several fungal species including Lasiodiplodia and Dothiorella spp. have been reported to be associated with this disease in regions where avocado is grown. The aims of this research were to identify the fungal pathogens associated with the stem-end rot of avocado in Sri Lanka based on morphological characteristics in combination with molecular and phylogenetic analysis. Diseased avocado fruits were collected from local markets and causal agents were isolated. Colony morphology and characteristics of conidia were observed using phase-contrast microscopy. Sequence analysis was performed using internal transcribed spacers (ITS) of the ribosomal DNA followed by phylogenetic analysis. Four endophytic fungal isolates were identified and designated as SER 01, SER 02, SER 03 and SER 04 which were distinguished respectively as Lasiodiplodia theobromae, Lasiodiplodia hormozganensis, Diaporthe nelumbonis and Fusarium oxysporum. To our knowledge, this is the first evidence on the occurrence of L. hormozganensis, D. nelumbonis and F. oxysporum associated with SER of avocado in Sri Lanka. Identified pathogens were proven to be collectively pathogenic to avocado following demonstration of Koch's postulates. The average value of collective disease severity after seven days of inoculation of avocado cv. Pollock was 40% at 28 C and it always fluctuated between 30% and 45%.

Powdery mildew of Rambutan (Nephelium lappaceum) incited by the fungus Oidium nephelii attack young leaves, flowers and immature fruits become dis-colored and dry off causing fruit quality deterioration and heavy fruit losses. Oidium nephelii is controlled by application of fungicides.