Managing root grub menace
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Affected plants exhibit yellowing and wilting of leaves
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ROOT GRUBS are notorious polyphagous pests. The fleshy grubs are highly destructive to the roots, rootlets and underground stalks of several crops.
Both adults and grubs cause damage. The beetles become active with the onset of summer showers during May-June.
Nocturnal variety
They are nocturnal and feed on neem leaves and a variety of other plants.
The female lays about 60-70 eggs in the moist soil at 7 to 15 cm depth. Incubation period lasts for 20 days and pupal period is about 25 days.
The adults emerge with the first monsoon showers. They are dark brown in colour. Affected plants show drying preceded by yellowing and wilting of leaves.
Infested plants can be easily pulled from the ground as their root system is severely affected.
Pest management
— Collect and destroy adult beetles attracted to nearby trees like neem, ailanthus and acacia during monsoon season. Set up light traps or bonfire to attract the adults between 6 to 9 p.m. during monsoon showers.
— Grow sunhemp as a trap crop to attract adults.
— Hand pick and destroy the adult and grubs in the field.
— Plough soil in summer to expose the pupae in soil, which will be picked up by the predatory birds and other natural enemies.
— Fork the soil during the fallow (January-March) period to collect the pupae and again during July to collect the second instar grubs.
— In case of severe infestations, apply quinalphos at the rate of 2.5 kg in one litre of water per hectare during August to December.
— Apply any one of the following insecticides to the soil: Malathion 5D 25kg or endosulfan 4D 30kg or methyl parathion 2 per cent dust 25kg/per hectare twice at fortnightly intervals after first summer rains.
N. DHANDAPANI
& M. ALAGAR
Department of Agricultural Entomology
TNAU, Coimbatore
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