Suppression of rice leaf mite pest
The rice leaf mite Oligonychus oryzae has attained pest status in the Cauvery delta regions of Tamil Nadu.
The infestation starts from the nursery till stem elongation stage. Leaf mites feed on upper and lower surface of rice leaves.
Usually they are more numerous on lower surface than upper surface.
The mites are small and microscopic and pierce the leaf tissues and suck the sap. They multiply very fast under congenial conditions and damage the entire leaf portion.
Life cycle
The entire life cycle can take 8-12 days. The adults are sexually mature when they emerge and mate as soon as possible.
Egg laying begins in 1-3 days. Flattened spherical straw coloured eggs are laid singly in rows along the leaf midribs and veins. Incubation lasts 4-9 days.
This is followed by the three immature stages — larva, protonymph and deutonymph.
This mite is active and breeds throughout the year building large populations during hot weather when the life cycle lasts the shortest time.
The damage is most serious during summer months when the temperature is high and humidity is low compared to winter and rainy seasons.
Management
Use chisel ploughing once in four years. Maintain the organic carbon content of the soil at optimum level.
Create a rice free period by ploughing down stubbles between crops or fallow crops with pulses and green manures in endemic areas. Maintain the bunds free from weeds.
Provide seed treatment/seedling treatment/main field application with pseudomonas flourescens at 10g/kg of seeds; 2.5 kg/ha seedlings; 2.5 kg/hectare of main field.
Top dress urea with neem cake (5:1) with LCC (leaf colour chart) based N to avoid excess nitrogen application and top dress with 50 per cent potash fertilizer.
In case of severity of mites foliar spraying of acaricides such as diafenthiuron 50WP 900 gm/ha or fenpyroximate 5SC 600ml/ha with wettable sulphur 40 WP 1.5 kg/ha if needed is recommended. .
S.M. Jalaluddin
Ravi G. & S. Jebaraj
Tamil Nadu Rice Research Institute, TNAU, Aduthurai , Tamil Nadu
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