Management of the american serpentine leaf miner Liriomyza trifolii (Burgess) Dietars on cowpea, Vigna unguiculata (L.) Walp

Abstract

Survey conducted in Kailiyoor panchayat of Thiruvananthapuram district revealed that Liriomyza trifol ii caused maximum damage to cowpea at the reproductive phase of the crop III summer. Raising susceptible varieties, applying high doses of nitrogen and frequent use of insecticides were noted to intensify the pest incidence. The weeds, Achyranthus aspera, Amaranthus viridis, Cleome viscosa, Cleome monophylfa, Heliotropium indicum, Physalis minima and Desmodium gyrans were identified as host plants of the pest. Seven larval parasitoids were recorded of which Chrysonotomyia rexia and Asecodes sp. were predominant. Twenty accessions of ccwpea including trailing and bush types were screened in the laboratory for resistance to L. trifolii. Accessions of trailing type were more susceptible to the pest. VU-12 was least susceptible among the trailing type while Sharika and Vyjayanthi were highly susceptible. Among the bush type, VU-4, VU-6, VU-3 and Arka Garima were less susceptible. Four plant oils and four synthetic insecticides when evaluated in the laboratory at two doses along with neem oil (2.5 per cent) and dimethoate (0.05 per cent) showed no significant diffe. ence in efficacy between the doses. Neem oil, marotti oil and ilIupai oil at 2.5 per cent and abamectin, 0.003 per cent, thiamethoxam, 0.02 per cent and profenophos, 0.025 per cent were found to be effective in controlling the pest. All the treatments reduced the pest infestation significantly in the field. Abamectin, 0.003 per cent was significantly superior. Neem oil, marotti oil and illupai oil 2.5 per cent also reduced pest infestation. Considering the cost and safety to the natural enemies, the oils were found more advantageous to the farmers.

Based on the results, cultivation of the tolerant accession VU -12 111 endemic areas, destruction of weed host plants, judicious application of nitrogen and need based application of neem oil / marotti oil / illupai oil at 2.5 per cent can be recommended for inclusion in rPM strategies of L. trifolii.