(Calocoris angustatus and Eurystylus oldi)
Credits: Biovision-Infonet
Nymphs and adults of the head bug (Calocoris angustatus) and the African head bug (Eurystylus oldi) feed on developing kernels as panicles emerge from the boot.
Head bugs are small (3 to 5 mm long, and about 1 mm wide) and variable in colour from yellowish green (C. angustatus), or pale brownish-yellow to dark brown with red markings (E. oldi).
Females insert long, cigar-shaped eggs between the glumes or anthers of sorghum florets. Eggs usually hatch in less than a week. Nymphs and adults suck juice from developing kernels as panicles emerge from the boot. Kernels attacked early in development are shrivelled, small, and off-coloured, resulting in yield loss.
Bug-damaged kernels become infected by secondary pathogens that further deteriorate grain quality. Feeding punctures are visible on older kernels. The life cycle is completed in about three weeks.
At least two generations feed on the same crop when panicles in the field do not mature at the same time.
What to do:
- Conserve natural enemies. Assassin bugs and lygaeid bugs prey on ear head bugs.
- Selection of varieties. Open panicles are less affected than compact panicles.
- Resistant varieties. Some sorghum varieties are resistant to bugs.
- Timing of planting. Damage is less severe when kernels develop during dry periods.