Ropiness test

A guide to the ropiness test

Contents of suspect cells, and especially cells containing larvae or pupae that are coffee-brown in colour and have no body segmentation, can be diagnosed for AFB using the ropiness test.

To perform the test, insert a small stick (e.g. end of wooden matchstick) into the suspect larva or pupa. Use the stick to mix up the brood remains, and then remove the stick slowly. If the suspect larva/pupa has AFB, the tissues will draw out in a fine thread between 10mm and 30mm long (Fig. 29). The thread will be of an even colour and consistency and will “snap back” when the thread breaks.

Figure 29: An AFB infected larva being roped out with a matchstick

Potential problems with the ropiness test

The ropiness test is not always a definitive diagnosis for AFB, however.

Diseased larvae or pupae in the early stage of decomposition, and those that have started to dry, may not “rope out” to any noticeable extent. As well, diseased larvae or pupae that have dried down completely to scale will not rope out, since there will not be any liquid material left in the cell.

It is important to use a dry stick with a rough surface to carry out the test. Remains of brood with AFB may not stick well to smooth or wet material like grass stems, and may therefore not rope out as far as they would normally.

If the larval material ropes out, but not as far as described above, look for other larvae and pupae that may show symptoms. If none are found, arrange to send the suspect larva to a laboratory to be tested (see laboratory diagnosis of AFB), or mark the hive and check it at regular intervals for six months or more.

Use the ropiness test to identify suspected AFB larvae and pupae.

Next >>