Non-circulative viruses: non-persistent or semi-persistent transmission

The non-circulative viruses are acquired during the trial feeding operations.  A trial attack of just a few seconds to a minute is enough to acquire the virus. The viral particles hitch onto the aphid stylets which can immediately transmit them to another plant (there is no latent period). This mode of transmission whereby the virus does not stay long in the aphid is termed non-persistent. The aphid quickly loses its retention capacity, in general after a few tens of minutes to several hours. It cannot contaminate other plants unless it reloads:with virus.                                                                     

In this transmission mode, there is no strong specificity and one virus can be propagated by many different species of aphids. Hence many aphids non-dependent on a particular crop can play an important role in viral transmission just by their shallow prospective attacks. Potato virus Y (PVY), for example, can be transmitted by over 70 species of aphids including Poaceae aphids such as Rhopalosiphum padi.

Another mode of transmission is known as semi-persistent. In this situation the viruses are localized in the phloem vessels, meaning that if the aphid is to reach and acquire them its stylets must be inserted more deeply. This type of piercing action corresponds to a longer feeding phase than that of the trial injection. The serious beet yellow virus (BYV) and the cauliflower mosaic virus (CaMV) are transmitted by way of this mode.