Scientific Opinion: Improving the Definition of Grape Phylloxera Biotypes and Standardizing Biotype Screening Protocols

Grape phylloxera biotypes are defined by their specific performance on, or preference for, a particular host (e.g., feeding on a particular rootstock). Numerous studies have phenotyped phylloxera biotypes, particularly with regard to their performance on various hosts, but the results are difficult to compare because there is neither a homogenous nomenclature nor a standardized protocol for phenotyping. To improve communication within the scientific community, we offer a simplified phylloxera biotype classification to allow clear data interpretation and effective communication. We also introduce the standard techniques employed for phylloxera phenotyping and discuss their advantages and disadvantages.