Small-scale glasshouse test identifies a new biotype of Russian wheat aphid in South Africa.

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The actual driver of the development of resistance breaking biotypes needs to be identified. While the most likely and plausible explanation is the use of resistant cultivars, it is important to identify what aspect of the "resistant cultivar" is the largest driver of aphid biotype formation. Is it: The resistant cultivar in-field during the crop season? The resistant cultivar as alternate host during the non-crop season or the combination of both? Was the formation of the resistance breaking biotype in anyway expediated by the combination of the host plant resistance and any other factor ie drought stress, excessive moisture, heat stress? It is known that RWA can enter the sexual phase in very cold environments at high altitudes. This phase has not been reported for RWA in Southern Africa, but these conditions occur in the highlands of Lesotho. We know RWA over summers there, just because we haven't found sexuals yet doesn't mean they do not occur .... Knowing the answers to these questions will assist in managing future RWA resistant cultivars, which will likely contain stronger resistance and could also be followed by the development of other resistance breaking biotypes of RWA.

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