Toward an improved understanding of the dynamics of vineyard-infested Scaphoideus titanus leafhopper populations for better timing of management activities

Background: This paper deals with supervised management of Scaphoideus titanus (Homoptera Cicadellidae) and describes a phenology model designed for improving the understanding of the within-vineyard dynamics and the timing of insect growth regulator (IGR) applications. RESULTS: The model consists of five components dealing with (a) the beginning of the post-dormancy development of overwintering eggs, (b) the egg hatching patterns, (c) the duration of first-instar nymphs, (d) the development and survival of subsequent instars and (e) the stochastic development of cohorts and their passage into the adult stage. Laboratory data permitted the parameterisation of temperature-dependent development and survival functions. Field data consisting mainly of beating tray catches allowed model parameterisation and validation. The model satisfactorily predicts the dynamics of age structures, the beginning as well as the pattern of egg hatching, the occurrence of the third instar and the emergence of adults. CONCLUSION: The phenology model is useful for timing IGR applications and for setting up monitoring activities in supervised S. titanus control. The model is an entry point into an adaptive management system, in that real-time weather and monitoring data are continuously integrated into the model for improving its explanatory and predictive capabilities

Multiannual infestation patterns of grapevine plant inhabiting Scaphoideus titanus (Hemiptera: Cicadellidae) leafhoppers

The Nearctic leafhopper Scaphoideus titanus Ball (Hemiptera: Cicadellidae) was accidentally introduced in Europe, where it became the vector of the \u2018Candidatus Phytoplasma vitis\u2019 phytoplasma causing the \u2018Flavescence dore\ub4e\u2019 disease of grapevine plants. A time-varying distributed delay model, simulating the successive occurrences of egg hatching, nymph presence, and adult emergence, is extended here to represent multi-generation infestation patterns of grapevine plants inhabited by eggs, nymphs, and adults. The model extension includes intrinsic mortality, mortality caused by plant dormancy, and low temperatures, development of diapausing and postdiapausing eggs, fecundity rates, and adult longevity. Field observations and published data were used to estimate parameters. The model was validated with five years canopy infestation data from five vineyards not subjected to insecticide treatments and found to have satisfactory explicative and predictive qualities. The model output is most sensitive to a 10% variation in the upper threshold and in the shape parameters of the survivorship function and least sensitive to a 10% variation in the shape parameters of the development function and the survivorship level. Recommendations are made to take into account other factors than temperature and plant phenology and include a wider geographical area in further model development.La cicadelle ne\ub4arctique Scaphoideus titanus Ball (Hemiptera: Cicadellidae) a e\ub4te\ub4 introduite accidentellement en Europe dans les anne\ub4es \u201850, ou` elle est devenue le vecteur du ) Candidatus Phytoplasma vitis * responsable de la maladie de Flavescence dore\ub4e de la vigne. Un mode`le de de\ub4lai distribue\ub4 dans le temps (time-varying distributed delay model), simulant les e\ub4ve`nements successifs des e\ub4closions, de la pre\ub4sence des stades juve\ub4niles et de l\u2019e\ub4mergence des adultes, a e\ub4te\ub4 e\ub4tendu pour repre\ub4senter les niveaux d\u2019infestation multi-ge\ub4ne\ub4rationnels de la vigne colonise\ub4e par des \u153ufs, des nymphes et des adultes. L\u2019extension du mode`le inclut la mortalite\ub4 intrinse`que, la mortalite\ub4 cause\ub4e par la dormance de la plante et les basses tempe\ub4ratures, le de\ub4veloppement des \u153ufs diapausants et post-diapausants, les taux de fe\ub4condite\ub4 et la longe\ub4vite\ub4 des adultes. Les observations au champ et les donne\ub4es publie\ub4es ont servi de base pour l\u2019estimation des parame`tres du mode`le. Le mode`le a e\ub4te\ub4 valide\ub4 avec les donne\ub4es de cinq anne\ub4es d\u2019infestation de la haie foliaire de cinq vignobles sans traitements insecticides et il a montre\ub4 des qualite\ub4s explicatives et pre\ub4dictives satisfaisantes. Le re\ub4sultat du mode`le est plus sensible a` une variation de 10% dans le seuil supe\ub4rieur et dans les parame`tres de forme de la fonction de survie et moins sensible a` une variation de 10% dans les parame`tres de forme de la fonction de de\ub4veloppement et du niveau de survie. Des recommandations sont faites pour prendre en compte d\u2019autres facteurs que la tempe\ub4rature et la phe\ub4nologie de la plante et inclure un plus large e\ub4ventail de zones ge\ub4ographiques pour un de\ub4veloppement ulte\ub4rieur du mode`le