Two species of tea mosquito bugs: Helopeltis thievora and Helopeltis antonii are the most important sucking pests of tea.
The nymphs and adults of these insects suck sap from terminal twigs, buds and leaves by piercing the plant tissues with their mouth stylets besides injecting toxic substances present in their saliva.
As a result of this injury, the leaves become curled up and deformed. The feeding punctures on leaves appear as reddish brown spots.
The attacked shoots may present dieback symptoms. Eventually the terminals of tea bushes will dry up leading to total loss of the crop. The process of egg laying also causes damages to the tender tissues.
Bio-ecology
Adult bugs appear black in color with red thorax and greenish brown wings. They look like any other mosquito species and hence the name mosquito bug.
A characteristic knob is present on the scutellum. These bugs are active early in the morning and late in the evening.
Each female bug can insert as many as 500 eggs in plant tissues. The eggs hatch in about a week's period by releasing the nymphs. After passing through five moltings they turn into adults in a fortnight's period. The entire life cycle is completed in about a month.
In a year there may be several generations. Adults hibernate during winter. These insects are active from January to September. Their damage is predominant in moist and shaded areas especially after monsoon showers.
Management methods
Monitor the pest in the field at regular interval. Collect the nymphs and adults by using hand nets at twilight hours.
Remove the tea bushes which provide moist and warm atmosphere. Grow resistant tea genotypes viz. TV6 and TV18.
Cultivate Annatto (Bixa orellana) as trap crop on the contours of the plantation.
Certain parasitoids exert biological control of these insects in nature. Spray chlorpyrifos 20EC or malathion 50EC or Indane20EC or phosalone35EC @2ml/lit of water.
Application of the mixture of quinalphos+dichlorvos may also be resorted to at spray intervals depending on the intensity of incidence.
Spraying of insecticides should be started from the periphery of the infested plantations to trap the migratory and escaping population.
J. Jayaraj & S. Manisegaran
Agricultural College and Research Institute Madurai
