Control of three-cornered alfalfa leafhopper (Spissistilus festinus) and other common insect pests in vineyards through application of ground cover treatments

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Presenting Author(s)

Kristen Flores

Oakland, CA

Co-Author(s)

KM

Kelsey McCalla

University of California Berkeley
Berkeley, California
Alexis Billings

Oakland, CA
Houston Wilson

University of California
Parlier, California
KD

Kent Daane

University of California Berkeley
Parlier, California

Red blotch disease, which is caused by grapevine red blotch associated virus (GRBaV), compromises the quality and yield of grapevines in vineyards throughout the world. While its global spread indicates human-mediated transmission, the continued spread within vineyards suggests that insect vectors may also play a role. Studies to date that have surveyed common vineyard insects have found that the three cornered alfalfa hopper (Spissistilus festinus) is capable of transmitting the virus in greenhouse experiments. In this study, we compared the application of two groundcover management strategies on the populations of S. festinus and other insect pests and GRBaV candidates, most notably Scaphytopius graneticus. Our goal was to target the groundcover-dependent S. festinus nymphs before they could grow into adults and migrate to the vine canopy. We found five times more S. festinus in rows that had been mowed compared to rows that had been disced but little difference in the populations of S. graneticus between treatments. However, we recovered 50 times more of these insects than we did S. festinus. These preliminary results suggest that managing groundcover is an effective alternative to pesticides for controlling the GRBaV vector S. festinus. However, the low densities of S. festinus in the vineyard canopies may indicate that other insect vectors may be responsible for the spread of the disease. Further studies will examine the potential of S. graneticus as a GRBaV vector.