Detection of citrus greening disease and field efficacy of anti-pathogen chemicals against the disease in mandarin (Citrus reticulata Blanco.) in Gulmi, Nepal

Abstract

Citrus cultivation in Nepal faces a persistent decline due to the widespread prevalence of Huanglongbing (HLB), also known as Citrus Greening Disease, across citrus-growing regions. This has resulted in significant economic losses for farmers, prompting them to actively seek preventive and remedial measures. In a study conducted at Resunga Municipality and Dhurkot Rural Municipality, Gulmi, aimed at addressing this decline, 51 orchards were assessed for HLB using the starch iodine test. Concurrently, the efficacy of anti-pathogen chemicals in managing citrus greening disease in mandarin (Citrus reticulata Blanco) was evaluated. An experiment was designed, incorporating eight treatments in a Randomized Complete Block Design (RCBD) with three replications. Each replication included eight treatments designated as follows: T1: Neem oil 5ml/l + Lentinan 2ml/l, T2: Neem Oil 5ml/l + B. amyloliquefacians 5ml/l, T3: Neem oil 5ml/l + Pseudomonas 5ml/l, T4: Imidacloprid 0.02% + Copper Oxychloride 0.025%, T5: Imidacloprid 0.02% + Streptocycline 250ppm, T6: B. thuringiensis 2ml/l + Pseudomonas 5ml/l, T7: B. thuringiensis 2ml/l + B. amyloliquefacians 5ml/l, T8: control. Results revealed that among the orchards tested, 18 were positive for HLB, representing 35.2% of the sample size. Notably, plots treated with Neem oil + B. amyloliquefacians and B. thuringiensis + B. amyloliquefacians exhibited the most significant reduction in disease severity compared to the control. Based on these findings, foliar application of Neem oil at a concentration of 5ml/l along with B. amyloliquefacians at 5ml/l, and B. thuringiensis at 2ml/l along with B. amyloliquefacians at 5ml/l at monthly intervals showed promising results in reducing the severity of citrus greening