PROCEEDINGS SHO Horticulture Department Series 491 January 1980 OHIO AGRICULTURAL RESEARCH ~~W' WOOSTER, 0 CONTENTS Page No. The Effective Use of Fungicides for Controlling Grape Diseases 1 by M. A. Ell is The Grape Industry in Virginia 4 by E.L. Phillips , Developing a Wine Industry in Mississippi.............................. 8 by R.P. Vine, B.J. Stojanovic, C.P. Hegwood, Jr., J.P. Overcash and F.L. Shuman, Jr. Use of Methiocarb in Ohio Grapes •...................................... 12 by R.N. Williams Maintaining Correct Levels of Free Sulfur Dioxide in Wines 14 by J.F. Ga11ander and J.R. Liu Centrifugation of Musts and Wines 18 by F. Krampe Microbiological Testing for Predicting Wine Stability 24 by A. Haffenreffer Importance of Determining Volatile Acidity in Wines 26 by J.F. Gallander Preliminary Observations of Cluster-Thinning and Shoot-Tip Removal On 'Seyval' Grapevines, by G.R. Nonnecke 29 Concepts of Making Red Table Wines 32 by R.P. Vine Environment and the Variety............................................ 38 by E. L. Ph i 11 i ps Integrated Pest Management and You ~................ 44 by F. R. Ha 11 A Progress Report on the Effects of Rootstocks on Five Grape Cultivars.. 49 by G.A. Cahoon and D.A. Chandler PREFACE Approximately 150 persons attended the 1980 Ohio Grape-Wine Short Course, which was held at the Fawcett Center for Tomorrow, The Ohio State University, Columbus, Ohio, on January 29-30. Those attending were from 9 states not including Ohio and represented many areas of the grape and wine industry. This course was sponsored by the Department of Horticulture, The Ohio State University, in coopera­ tion with Ohio Agricultural Research and Development Center, Ohio Cooperative Ex­ tension Service and Ohio Wine Producers Association. 1/80-1200 THE EFFECTIVE USE OF FUNGICIDES FOR CONTROLLING GRAPE DISEASES M. A. Ellis Department of Plant Pathology Ohio Agricultural Research and Development Center In 1859, Ohio led the nation in grape production. Most production was center­ ed around Cincinnati and eastward along the Ohio River. By 1870, diseases (pri­ marily downy mildew and black rot) eliminated much of the grape industry. At pre­ sent, the grape industry is growing in Ohio; however, disease is still one of the major factors limiting production. The most common and economically important di­ s~a~es of grape in Ohio are caus~d by f~ngi: Dow~~ mildew, caused by Plasmopara vltlcola; black rot, caused by Glugnardla bldwellll; powdery mildew, caused by Uncinula necator; bunch rot, caused by Botrytis cinerea; and bitter rot, caused by Melanconium fuligineum, are diseases that remain a constant threat to the commer­ cial production of grapes in Ohio. All commercial varieties grown in Ohio are sus­ ceptible to most or all of the above diseases. The introduction and acceptance of resistant varieties is highly unlikely within the next 10 years. Therefore, the use of fungicides for controlling these diseases is essential for the continued de­ velopment of the Ohio grape industry. Fungicides for control of most grape diseases are presently available. Whereas some fungicides may be more effective than others for controlling a specific disease, it must be remembered that the effectiveness of any fungicide is largely dependent upon how and when it is used. To use any fungicide effectively, the following points must be considered: 1) correct disease identification, 2) selection of the proper fungicide, 3) proper timing of application, and 4) thorough coverage of all suscepti­ ble plant parts. Correct Disease Identification It is essential to know what specific disease or diseases are present in order to choose the proper fungicide and determine the proper timing of application. Sev­ eral diseases commonly occur together in the same vineyard and can be easily con­ fused, especially on the fruit. One of the best examples is black rot and bitter rot. These two diseases cause similar symptoms on fruit and are often confused; however, differences in disease control practices make it essential for growers to correctly identify them. Black rot infects only young green berries. As berries begin to ripen (change color), they become resistant to black rot. Bitter rot is a disease of ripe berries and does not appear until fruit is about full size and be­ ginning to ripen. Fungicide sprays for black rot control are generally started early in the season and are terminated as berries begin to mature. If bitter rot is present and preharvest weather is warm and wet, the termination of fungicide sprays too early could result in serious losses. For help in disease identification it is recommended that growers contact their county extension agent. In many cases the agent can identify the disease. If the agent cannot identify the disease, he can send samples to the Plant Disease Clinic at The Ohio State University for diagnosis. Selection of the Proper Fungicide Correct disease identification leads to the selection of the correct fungicide. The most effective fungicides currently available have been developed for specific -1- situations and specific diseases. Usually, there are several fungicides that are effective for a specific disease but it is unlikely that a specific fungicide will control all diseases. For this reason fungicide combinations may be needed. In southern Ohio, black rot and downy mildew must be controlled at the same time throughout the growing season. The most effective fungicide for black rot may not be the most effective fungicide for downy mildew. In situations such as this, a combination of the most effective fungicide for each disease (provided the fungi­ cides are compatible) may result in more effective control. Read the label before selecting any fungicide. It is a violation of the federal pesticide law to use a chemical in any manner inconsistent with the label. For current fungicide recom­ mendations and information on compatibility for mixing, Ohio growers should obtain a copy of the Ohio Commercial Fruit Spray Guide from their county extension agent. Proper Timing of Application Proper timing means consideration of when and how frequently the fungicide must be applied to effectively control the disease. Most fungicides currently available for grape disease control are protectants. They function by forming a protective barrier on plant surfaces and must be applied before the fungus arrives on the plant surface and enters the plant. The black rot and downy mildew fungi can enter a susceptible plant within a few hours under favorable environmental conditions. Once fungi are inside the plant tissues, protectant fungicides will not stop infec­ tion. Therefore, proper timing of spray applications is critical. After the first application, the fungicide barrier is established on the plant surfaces. Effective fungicide use involves keeping this barrier active throughout the time that the fungus can arrive on and infect the plant. For control of black rot and downy mildew the fungicide barrier needs to be present throughout most of the growing season. r10dern fungicides are developed so that they do not persist in the environment for very long. Some of the factors that affect fungicide degradation include: rain water, microbial action, oxidation, and sunlight. Due to degradation and washing away of the fungicide by rain, proper timing of additional applications are impor­ ant. Plant growth also affects the completeness of the protective fungicide barrier. As new leaves and shoots are produced, they must be covered with the fungicide bar­ rier. Reapplication guidelines are given on the fungicide label. The guidelines usually are in ranges, such as "spray at 7-14 day intervals." If excessive rainfall or excessive growth of the crop is occurring, the shorter interval should be used. Thorough Coverage of all Susceptible Plant Parts Regardless of what type of equipment is used to apply fungicides, thorough CQV­ eraqe of all susceptible plant parts must be obtained. Any portion of the plant sur­ face not covered by fungicide is open to attack by disease-causing fungi G The black rot fungus can penetrate grape leaves through the upper and lower surface. The downy mildew fungus penetrates leaves through the lower surface. No matter how many times a plant has been sprayed, if the lower surface of the leaf is not covered with fungicide, it is still subject to attack by these fungi. Completeness of the pro­ tective barrier of fungicide is essential for effective disease control. The com­ pleteness of the barrier is partly dependent upon how well the spray spreads and sticks to the plant surfaces. For this reason, spreader-stickers or spray adjuvants are often added to fungicide sprays. Careful consideration of proper disease identification, selection of the proper fungicide or fungicides to do the job, proper timing of applications, and thorough coverage of all plant parts will go a long way towards increasing the effectiveness -2- of fungicide spray programs for controlling grape diseases. -3- THE GRAPE INDUSTRY IN VIRGINIA E. L. Ph i 11 i ps Department of Horticulture Virginia Polytechnic Institute &State University Virginia has the "wine fever ll again. For the tenth time since the founding of Jamestown in 1607, a serious attempt is being made to establish a viable grape in­ dustry in the Old Dominion. With no less than eight distinct species of the genus Vitis growing wild within its borders, it is difficult to understand why the indus­ try is so little developed at the present time. The Past From the very earliest days of lJamestown, the colonists cultivated lithe vine". Lord Delaware, governor of the colony in 1610, persuaded the London Company to sub­ sidize the culture of the grape as a possible source of revenue. French vine dres­ sers were brought over for this purpose, but the results were disappointing. The vine grew profusely and the yields were good, but the wine from the native American grapes was "strong and heddy".