2007 Research Reports

Systemic Insecticides for Selective and Targeted Insect Control in Michigan Vineyards
Rufus Isaacs, Steve Van Timmeren, John C. Wise
Department of Entomology, Michigan State University
Abstract: The grape industry is gaining registrations of systemic insecticides that can be delivered through the vine roots after application to the soil. This project tested various systemic insecticides and showed that they can provide high levels of vine protection against potato leafhopper and Japanese beetle depending on the application timing and application method. They have the added benefit over conventional insecticides of being most effective in new shoot growth where potato leafhopper infestation is greatest. We also detected reduction in grape berry moth in one of the study years, and there was no consistent effect on soil-dwelling beneficial insects. Soil applications at commercial farms were effective only in vineyards using drip irrigation, suggesting that vines must have root systems near to the emitters for this approach to be most effective.

Delivery of IPM Information to Increase Adoption of Reduced-Risk Practices in Michigan Vineyards
Rufus Isaacs, Steve van Timmeren, Annemeik Schilder, Joy Landis, Mike Brewer, Mark Longstroth, Duke Elsner and Nikki Rothwell
Michigan State University
Abstract: During 2007, we set up four demonstration vineyards that were used to showcase the effectiveness of reduced-risk insecticides and fungicides. IPM workshops were held at three of the four demonstration vineyards, allowing for hands on training of growers in vineyard scouting practices and education on the use of reduced-risk pesticides. Scouting at each of the demonstration vineyards took place each week with scouting data compiled into a weekly report that was made available online at www.grapes.msu.edu. Analysis of scouting data indicates that the reduced-risk insecticide Intrepid® provided better protection against grape berry moth than standard insecticides and the reduced-risk fungicide ProPhyt® provided excellent control against downy mildew. Dormant fungicides were used in these vineyards, but their contribution to disease control is not clear given the other treatments applied. Information from this project has been distributed widely to the Michigan grape industry in meetings and workshops to educate growers on the benefits of reduced-risk insecticides and fungicides. The findings of this project are being integrated into an IPM Workbook being developed at MSU. We hope to continue this extension effort to allow greater opportunities for education of growers about scouting, performance of these new tools, and to track their adoption.

Development and Evaluation of Crown Gall-Free (Agrobacterium vitis) 'White Riesling', 'Chardonnay' and 'Cabernet franc' Grapevines
Thomas J. Zabadal
Department of Horticulture, Michigan State University
Abstract: Approximately 500 vines of the Cabernet franc variety grafted to the rootstock C3309 had been propagated in the summer of 2004. In the spring of 2005 those vines were distributed to cooperators in five states. First ratings of vine survival and the development of crown gall on vines in this experiment were assessed in the fall of 2006. Approximately three-fourths of those evaluations have been summarized to date. They indicate no loss of vines to winter injury and/or crown gall and a need for modest replanting of vines.

Evaluating Pre- and Post-Infection Powdery Mildew Control Strategies in Wine Grapes
Annemiek Schilder, Nikki Rothwell
Michigan State University
Abstract: Powdery mildew, caused by the fungus Uncinula necator, is a disease that affects many wine grape varieties and is responsible for numerous fungicide applications during the season. Once powdery mildew has started, it is difficult to eradicate, since environmental conditions during most of the summer tend to be suitable for disease development. The powdery mildew fungus does not need free water, just moderate temperatures and moderate to high relative humidity to continue its development and spread. Several new fungicides have come on the market in recent years that (claim to) have powdery mildew activity, including Quintec, Endura, Pristine, Prev-Am, Oxidate, etc. Most of these products are considered reduced-risk, in that they have low mammalian and environmental toxicity. Using multiple chemistries in a disease control program is important to achieve optimal disease control and reduce the chances of fungicide resistance development in the powdery mildew pathogen, which is a real risk as shown by the occurrence of resistance to strobilurins in grape powdery mildew in New York. There are some suspected cases of resistance to sterol inhibitors in Michigan as well. In order to improve management recommendations and the ability of growers to control powdery mildew in Michigan, this proposal aims to evaluate various reduced-risk fungicides and fungicide programs for their efficacy in preventing and eradicating powdery mildew infections.

Understanding host specificity of Plasmopara viticola on grapes
Annemiek Schilder, Nikki Rothwell
Michigan State University
Abstract: Downy mildew, caused by the fungus-like pathogen Plasmopara viticola is a serious disease of grapes worldwide, leading to destruction of fruit clusters and leaves. This disease has been found on cultivated grapes (e.g., the European wine grape and fox/juice grape) as well as wild grapes (e.g., river bank grape, summer grape). This research project showed that downy mildew is not the same on all grape species.