Wind-mediated Dispersal of Beet Leafhoppers and Pine Pollen in Southern Idaho

Abstract

The management of beet leafhoppers (BLHs) is important for disease control since BLHs can vector important plant pathogens such as curly top viruses and phytoplasmas in southern Idaho. Historical data for southern Idaho suggests that BLH need approximately 130 growing degree days (GDDs; 12.8°C base) to initiate dispersal and around 382 GDDs until they reach peak dispersal. A recent study in southern Idaho identified large peak dispersal events of BLHs on May 19, 2020 and June 2, 2021 in Elmore Co. near Mt. Home, ID. Historically, BLH have been thought to originate from local areas. However, based on GDDs and dispersal numbers under optimal conditions for Mt. Home, the BLHs likely did not originate from local areas. Data for wind and pine pollen dispersal combined with GDDs for areas known to contain BLH suggest that the BLH could have originated outside the local area and possibly up to 142 to 515 km away. At least five conditions appear to be necessary for observation of BLH dispersal into southern Idaho: a wind event must occur (35 km/h avg. hourly wind speed), dispersal temperature threshold (16 to 18°C) must be met, >130 GDDs must be accumulated to initiate dispersal, daily peak temperatures should reach 24°C, and attractive BLH vegetation such as Russian thistle must be present. Combining wind event forecasts with temperature parameters in the future may make it possible to provide targeted timely insecticide sprays for BLH control.