Pests and diseases of Aloe vera in West Bengal: field survey, pathogen identification, and biological Control
Abstract
A field survey and biological control study was conducted at the Horticulture Research Station (HRS), Mondouri Teaching Farm, Bidhan Chandra Krishi Viswavidyalaya, Mondouri, Nadia, West Bengal, during 2023–2024 to document the incidence and severity of pests and diseases affecting Aloe vera (L.) Burm. f. and assess the effectiveness of biological control agents under screenhouse and field conditions. Disease incidence was recorded at fortnightly intervals from six established plots. Mean disease incidence was highest for leaf spot/anthracnose (44.2%), followed by soft rot (32.6%), tip necrosis (27.4%), and root/crown rot (19.8%). Four fungal pathogens were isolated from symptomatic plants and identified by Internal Transcribed Spacer (ITS) sequencing: Colletotrichum siamense, Lasiodiplodia theobromae, Rhizoctonia solani, Curvularia hawaiiensis, Fusarium solani, and Penicillium purpurogenum. Among arthropod pests, Tetranychus urticae recorded the highest mean population (19.4 mite leaf-1), followed by Aphis gossypii (13.2 leaf-1), Hercinothrips dimidiatus (7.1 leaf-1), and Pseudococcus spp. (4.6 leaf-1). In screenhouse trials, Trichoderma asperellum isolate T₃ reduced C. siamense severity by 77.4% and increased plant fresh weight by 144.3%. T. harzianum reduced R. solani root rot severity from 85.0% to 5.0% (94.1% reduction). Under field conditions at Mondouri, integrated application of T. asperellum + 10% Aloe leaf extract gave the highest reduction in leaf spot severity (61.2% at 45 DAT) and the highest marketable leaf yield (47.8 t ha-1), with a benefit-cost ratio of 2.84, outperforming the chemical standard (2.11). Aqueous Aloe leaf extract (10% w/v) reduced T. urticae populations by 72.8% at 7 days, with an LC50 of 105 ppm for the acetone fraction. The results confirm that biologically based integrated management can replace a substantial proportion of chemical inputs in Aloe production in eastern India.