Development of larval instars of Empoasca vitis and Edwardsiana rosae(Homoptera: Cicadellidae) on grapevine leaves at different temperature regimes
Abstract: The polyphagous grape leafhopper Empoasca vitis (Homoptera: Cicadellidae) isregarded as a major insect pest in many European grapevine growing areas. Both larvae as wellas adults feed on the phloem vessels of the leaves, causing characteristic symptoms also referredto as hopperburn. While E. vitis is long known as a widespread insect in Southern Europeanvineyards, it has only just recently been recognized as an important pest in cooler climates suchas Middle European winegrowing regions. This increase in grape leafhopper population sizesmight be due to an increase in more favourable weather conditions maybe as a result of climaticchange. In addition, a couple of monitoring studies have shown that there are a numerous otherleafhopper species occurring in vineyards besides E. vitis as well. The rose leafhopperEdwardsiana rosae (Homoptera: Cicadellidae) is one of the leafhopper species occasionallyfound on grape vine leaves, with no data presently available on its putative potential to causeeconomic damage on grapevine. Here, we report on a first data set obtained in a laboratory studyon the development of larvae of two leafhopper species, E. vitis and E. rosae under five differenttemperature regimes on grapevine leaves. Single leaves of Vitis vinifera were collected in thefield between the beginning of May and mid August 2009, 2010 and 2011, respectively, and werescreened for the presence of leafhopper eggs in the veins of the respective leaves. Freshlyemerged larvae were transferred to new grapevine leaves and were kept solitary throughout theexperiment at the following night:day (N:D) temperature regimes: 10°C (N) – 20°C (D), 13°C (N)- 23°C (D), 15°C (N) – 25°C (D), 18°C (N) – 28°C (D), 20°C (N) – 30°C (D). These set-ups wereselected as typical night-day temperatures and putative climate change scenarios in middleEuropean viticulture. At least 30 larvae per species and temperature range were screened.Developmental time from first instar larvae to adult was shortest at the 15°C (N) – 25°C (D)temperature range. None of the individuals of both species completed development from the eggstage to first instar at the temperature regime of 20°C night and 30°C day temperature. At thistemperature range, either no egg hatch was observed or hatch of first instar larvae was notsuccessful. These results suggest that warm (18°C) nights and moderately warm (28°C) days arerepresenting the upper thermal threshold for development of both E. vitis and E. rosae embryonicstages on grapevine leaves, contradicting current assumptions of an increasing importance ofE. vitis as a grapevine pest under future climate change.