Pigeon Pea & Red Gram
Southern Green Stink Bug
Nezara viridula
Insect
5 mins to read
In a Nutshell
- Dry and shrivelled shoots.
- Fruit may not grow properly and even drop.
- Flowers may drop.
- Black hard spots on fruit.
Pigeon Pea & Red Gram
Symptoms
Bugs feed mostly on fruit and growing shoots. Growing shoots dry and fall back. Feeding on fruit causes the most of the damage. Fruit may not grow to their full size, change shape and even drop. In many cases feeding on fruits causes black hard spots on the fruit surface. Feeding on flower buds cause flower drop. Taste of fruit can be affected. The feeding spots can be an entrance point for pathogens to cause more damage. Egg masses can be found on the underside of the leaves.
Recommendations
Organic Control
The egg parasitoid Trissolcus basalis and the tachinid flies Tachinus pennipes and Trichopoda pilipes have been used successfully to control this pest.
Chemical Control
Insecticidal applications are usually not required/necessary, however sprays may be needed if stink bug populations are high. This pest can be chemically controlled by the use of carbamates and organophosphate compounds. However, since most of these compounds do not last very long on the treated plant, the crop is at risk of being infested again from nearby areas. The effectiveness of insecticidal control can be improved by taking advantage of the times when the pest is active and not hidden within the foliage. Therefore, the insecticides can come into direct contact with them. The stink bug is observed to feed during early morning and late afternoon.
What caused it?
The damage is caused by a bug called Nezara viridula, which is found all over the world, especially in tropical and subtrupical regions. They are called "stink bugs" because they release a strong odour when they feel threatened. The bugs feed by piercing the crop with their thin piercing mouth parts (stylets). The actual feeding puncture is not immediately visible. Both adults and juvenile stages of the bug feed on plants. They prefer to feed on the delicate parts of the plant (growing shoot, fruit, flower). When it hatches, the juvenile stage of the bug stays close to the eggs. The adults can fly and move around a lot. They are usually green and thus hard to recognize in plants. The colour of the bug changes as they grow, becoming greener with each stage. Usually they move to higher parts of the plants early in the morning.
Preventive Measures
- Remove leaf litter.
- Control the weed growth in your field.
- Plant crops earlier and with larger row width.
- Plant early maturing trap crops, like leguminous and cruciferous plants as these crops attract the bug.
- Plough the trap crop under before the southern green stink bugs become adults and move to the main crop.
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