Crops: Cole crops
Why is it a problem? Harlequin bugs can be damaging during the seedling stage and early stage of the crops in Bhutan. Concentrated attack causes widespread withering of young leaves. However, it rarely causes economic losses.
Where and when is it a problem? This pest is probably present and common in all Cole crop growing areas. Major, widespread outbreaks have not been reported.
Two very similar species of harlequin bug are commonly encountered in Cole crops in Bhutan (E. dominulus and E. liturifera). They need to be distinguished by a specialist. Adults are about 10 mm long that give an unpleasant odour when disturbed. They are either orange or reddish in colour with black spots. Eggs are barrel-shaped, greyish-white and about 0.5 mm in diameter. They are laid in batches of two overlapping rows.
Feeding causes whitish spots. Branch-like white stripes then radiate from the centre of the main spot. Plants with older damage present a “burnt appearance”.
Confusion with other pests: Their distinctive colouration means that adults are not easily confused with other pests.
Lifecycle: It is likely that harlequin bugs may produce two to three generations in a year in Bhutan.
Dispersal: Adults fly.
When can damage be expected? Damage has never been quantified in Bhutan, but significant outbreaks have never recorded.
Hosts: Both species are commonly found on Cole crops as well as mustard and radish.
This pest is rarely a problem, and then only for young Cole crop stages. Chemical control is only needed in the most severe cases.
Constant monitoring is required for this and other pests on Cole crops. The presence of bugs needs to be determined particularly during the early stages of the crop.
Effect of variety
- Destruction of crop residues in is an important cultural practice to limit harlequin bug damage in the following year.
- Chemical spray will rarely be justified, and should only be directed to where the pest is dense.
- Cypermethrin (1 ml per 1 litre of water) can be used. A waiting period of at least two weeks after spraying is needed before harvesting.
Image acknowledgements: NPPC.