PHYSICAL, BIOLOGICAL AND CHEMICAL CONTROL OF TAENIOTHRIPS SIMPLEX IN GLADIOLUS

The thrips is often introduced into the field crop with the planting stock and from it back again into storage with the harvested corms.
We investigated physical, biological and chemical control of thrips in the field and during storage.

Physical control

The effect on thrips and on thrips-induced damage of a cold period during storage was investigated.
It appeared that after being kept in cold storage for a minimum period of six weeks at 2°C or 8 weeks at 5°C, larvae, pupae and adult specimens died and eggs were no longer viable.
Hence, the corms were damaged no further.

Storage of corms at these low temperature, provided they were well-dried, proved not to be harmful to emergence and growth.

Biological control

Investigations as to the possibilities of biological control gave promising results.
The predatory mite Amblyseius barkeri mainly feeds on larvae of the thrips.
Extention of infestation by thrips during storage was prevented by introduction of this mite into batches of gladiolus corms.

Chemical control

Aldicarb and chlorpyrifos were applied as furrow treatment during planting.
Aldicarb prevented damage by thrips in leaf and flower, contrary to chlorpyrifos.
Chlorpyrifos had an after-effect on the harvested corms, aldicarb did not.

Acephate and omethoate proved very effective when applied in the field during the growing season.
For effective control, 2 – 3 sprayings during the growing season were sufficient, contrary to the chemical compounds advised in the Netherlands until recently, which often proved insufficient even with many more sprayings.