BISA advocates two release methods:
- Where the source of fly pupae is well defined, parasitic wasps can be released directly on the site, covering them with straw or other material available on site. In this case it is important to release the wasps with the onset of emergence from the fly pupae to minimize the chances of predation of wasps while still in the pupal case.
- Parasitised pupae can be placed in specially prepared containers on the fly breeding site. These containers protect the pupae against predators and adverse environmental conditions until the hatching of the wasps. The wasps then leave the container to search for fly pupae to feed on and to deposit their eggs. Containers must be placed as close as possible to the fly breeding site – wasps can disperse over a distance of approximately 50m, but nearer is always better. The use of containers has several advantages:
- Protection of the product against its natural enemies and adverse climatic conditions.
- Convenient and clean method of release.
- The product can be placed in the containers before the onset of wasp emergence.
Preparation of release containers.
Containers such as WHITE 1 liter or 2 liter buckets are ideal. The bottom and sides should be drilled full of 2mm holes, using a 2mm steel drill bit. Cover the bucket with holes to ensure proper air flow and drainage in case of rain. (The more holes the better).
Emptying sachets into buckets
The sachets containing the pupae should be opened and emptied into the bucket, closing the bucket properly afterwards. A 1 liter bucket will take 1or 2 sachets and a 2 liter bucket up to 4 sachets of pupae.
Placing the buckets
Place the buckets as close as possible to fly breeding sites (see paragraph above). Fix the bucket firmly to a branch or post, using a piece of wire, ensuring it is out of reach of animals to prevent damage. Also prevent the buckets from swinging excessively in windy conditions. In very hot areas, place the buckets in shady areas if possible, or create shade with grass or branches on top of the bucket.
Ants are important pupae predators. Where ants are a problem, the wire fixings on the buckets can be covered with an agent such as grease, to keep ants out.