FOLIAR GRAPE PHYLLOXERA, DAKTULOSPHAIRA VITIFOLIAE (FITCH), SEASONAL BIOLOGY, PREDICTIVE MODEL AND MANAGEMENT IN THE OZARKS REGION OF THE UNITED STATES

Abstract

The foliar morph of grape phylloxera (GP), Daktulosphaira vitifoliae (Fitch), is often a serious pest of wine grapes in the eastern United States. The objective of this project was to develop a management program for foliar GP in vineyards in the Ozarks region in the central United States. Studies were conducted on field validation of a laboratory-based GP degree-day (DD) model. Development from GP oviposition to adult required an accumulation of 303 DD (base 6.4°C). This model was used to restrict insecticide applications during the GP crawler (first instar) period in efficacy studies. In 2006, a vineyard was sampled to relate seasonal changes in GP growth stages in leaf galls to DD in Purdy, Missouri. By 1 May, ‘Norton’ vines had at least five expanded leaves and unopened flower clusters. GP egg counts per leaf were peaking and a few GP crawlers were present after an accumulation of 360 DD since late March. This DD value was in close agreement with the laboratory-based DD model which predicted second generation eggs by 303 DD and crawlers by 387 DD. In 2009, an insecticide efficacy study was conducted against foliar GP crawlers. Insecticide applications against third generation GP crawlers were applied on 16 June at 751 DD slightly after crawler emergence began. Treatments of two insecticides, fenpropathrin (Danitol) and spirotetramat (Movento), and a biopesticide, Surround kaolin clay, resulted in significant reductions in GP induced foliar galls by 14 August compared to untreated controls. The current recommended DD-based monitoring procedure for foliar GP crawlers is described.