Pomegranate
Pomegranate Stem Borer
Cerosterna scabrator
Insect
In a Nutshell
- Grubs dig holes on bark of main stems to feed on sapwood.
- Adult beetles chew at the green bark of younger shoots.
- Dry powdered frass material is usually seen near the base of plants.
Can also be found in
Pomegranate
Symptoms
Grubs dig holes on bark of main stems to feed on sapwood from inside. Adult beetles are active by the day and chew at the green bark of younger shoots. Holes on bark of main stems, excreta and dry powdered material are usually seen near the base of plants. Coelosterna spinator is not a specific pest of pomegranate trees. It is a polyphagous pest actually causing rather minor damage. It prefers breeding in dead wood but also attacks the living branches.
Recommendations
Organic Control
Damsel bugs, elm leaf beetle, some spiders, the big eyed bug (Geocoris spp.), parasitoid tachinid flies or braconid wasps are all natural enemies of the stem borer.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatmetns if available. Treat the holes by injecting with the appropriate insecticide and seal holes with clay. Foliar spray with chlorpyrifos (0.05%) also help to reduce populations of stem borer.
What caused it?
The symptoms described above are caused by larvae of Coelosterna spinator and several species of the genus Zeuzera. After pupation the adult beetle emerges by eating a circular hole through the bark. They are pale yellowish-brown and about 30 to 35 mm in length. They have light gray wing covers with a large number of black spots of different sizes and long bluish legs. Females lay about 20 to 40 eggs in an ovoposition cavity under the bark of young stems. About two weeks later, on hatching, the grubs start to feed on the soft tissues around them and then bore into the stem and roots. The length of the larval period is about nine or ten month.
Preventive Measures
- Timely planting will avoid peak populations of stem borer.
- Keep the right distance between trees or apply moderate to heavy pruning.
- Detect early infestation by periodically looking out for drying branches.
- Collect and destroy infected branches.
- Deep summer plowing exposes the dormant insect to predators and sun.
- Use plastic mulch helps to reduce pests and weeds.
- Uproot infested trees and burn them.
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