Herbicidal management of stem hemiparasite Dendrophthoe spp. in mango orchards

Dendrophthoe falcata is a stem hemiparasitic weed infesting tree crops. Manual removal of this parasitic weed is the common practice, often involving cutting the infested tree branches. However, it is labour-intensive and requires repeated removal due to regrowth. Even herbicidal sprays for selective control are unavailable and the use of conventional spraying methods often results in host toxicity. Hence, there is a need to develop targeted spraying methods. Therefore, a study was carried out during 2024–25 in a mango orchard at the College of Agriculture, Thrissur, in a completely randomized design (CRD), replicated thrice. The efficacy of various herbicides, application methods and sprayer types for controlling parasitic weed Dendrophthoe spp. on mango trees was studied. Treatments included foliar sprays of 2,4-dichlorophenoxyacetic acid (2,4-D) Sodium (Na) salt 80 wettable powder (WP) (5 g L-1), 2,4-D amine 58 soluble liquid (SL) (10 mL L-1), 2,4-D Na salt 80 WP (5 g L-1) + copper sulfate (CuSO₄) (20 g L-1), glufosinate ammonium 13.5 SL (10 mL L-1), metribuzin 70 WP (5 g L-1), ethrel 39 SL (25 mL L-1) and metsulfuron methyl 20 WP (0.4 g L-1); 2,4-D Na salt (2 %) and metribuzin (2 %) as padding at host-parasite junction, physical removal and untreated check. Ethrel induced complete defoliation within 2–3 days, followed by 2,4-D + CuSO₄, glufosinate ammonium, metribuzin and metsulfuron methyl. Defoliation was completed by 3–4 weeks in 2,4-D spray. Padding treatments were ineffective and no visual symptoms of phytotoxicity or reduction in physiological parameters were observed. Herbicide sprays reduced soluble sugars, protein, relative leaf water content, membrane stability, chlorophyll and nitrogen, phosphorus, potassium (NPK) content of Dendrophthoe. Foliar sprays of 2,4-D Na salt or 2,4-D amine provided sustained control without regrowth, whereas other herbicides provided only temporary suppression. Herbicide deposition rate, spray coverage and weed control efficacy varied with sprayer type. Compared to battery-powered hydraulic, backpack manually operated and air-assisted sprayers, the electrostatic sprayer recorded the highest spray deposition rate (30.5 µL cm-2) and lowest spray volume, but was ineffective. Though the deposition rate was low (10 µL cm-2), the battery-powered hydraulic sprayer provided superior canopy wetting with high volume spray and complete control. Targeted foliar application of 2,4-D with optimised sprayer technology provided effective control of Dendrophthoe in mango orchards, without host phytotoxicity. The study revealed a significant role of spray volume in herbicide efficacy, despite the electrostatic sprayers being highly efficient for disease and pest management.