Serpentine leaf miner is an invasive pest that was accidentally introduced in to India from America. It is a highly polyphagous pest infesting pulses, oil seeds, vegetables, green manures, ornamentals, fodder and fibre crops.
The adult insects are small in size and pale yellow in colour. The female fly thrusts its eggs on the lower surface of the leaves just below the epidermis which hatch in 2-3 days.
Emerging maggots mine into the leaf and feed on the tissues making serpentine mines. The pattern of mining is irregular and can greatly reduce the level of photosynthesis of the plant.
Several maggots mine on a single leaf and the infestation is usually seen on immature leaves. Due to severe infestation drying and dropping of leaves occur. Wounding of the foliage by maggots also make an avenue for the entry of bacterial and fungal pathogens.
The maggot becomes full grown in 7-18 days and full grown maggots are long, orange-yellow in colour. The maggots come out of the mine and pupate in the soil for 5-10 days. Indiscriminate use of insecticides are highly detrimental to naturally occurring biological control agents and also leads to development of resistance to the pest.
Some control measures
Collect and destroy the infested leaves Crop residues may serve as sources of inoculums, so destruction of weeds and deep ploughing are recommended.
Parasitoids like Chrysonotomyia often provide effective suppression of this pest in the fields. Hence use of disruptive insecticides is not advisable.
Placement of yellow coloured sticky trap at 100 numbers per acre will attract and kill adult flies.
Spray botanicals like neem oil emulsion, neem seed kernel extract. Insecticides like Dimethoate 30 EC (0.05 per cent) or Chloropyriphos 20EC (o.05 per cent) or Fipronil 0.3G (75gm/hectare) are recommended.
(M.T. Ranjith, Phd scholar and Dr. Mani Chellappan, Associate Professor, Department of Agricultural Entomology, College of Horticulture, Vellanikkara, Kerala Agricultural University, Thrissur, email: firstname.lastname@example.org, mobile: 09400681441 and 09447463522.)