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Content:

Freeze Warning this week!
Grape Hardiness and Frost Protection
Pest Awareness at Bud Swell
New Grape IPM website
Welcome TJ and Anton!
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Freeze Warning this Week!
By: Imed Dami, HCS-OARDC
 
 

A freeze warning (see below) has been issued by the 
National
Weather Service (NWS) in Eastern US including Ohio. Check the Eastern
region forecast Center at:
www.erh.noaa.gov. You may type
the
zipcode of your town for a local forecast. 

“…URGENT - WEATHER MESSAGE...CORRECTED
NATIONAL WEATHER SERVICE CHARLESTON WV
503 AM EDT WED APR 4 2007

...FREEZE WARNING IN EFFECT FROM 4 AM TO 10 AM EDT THURSDAY...

THE NATIONAL WEATHER SERVICE IN CHARLESTON HAS ISSUED A FREEZE
WARNING...WHICH IS IN EFFECT FROM 4 AM TO 10 AM EDT THURSDAY.
DUE TO THE UNSEASONABLY WARM WEATHER DURING THE MONTH OF MARCH...
IT IS DEEMED THAT THE 2007 GROWING SEASON IS NOW UNDERWAY FOR
SOUTHEASTERN OHIO...NORTHEASTERN KENTUCKY...AND SOUTHWESTERN
VIRGINIA. THIS IS PARTICULARLY TRUE OF BUDDING FRUIT TREES AND
PLANTS.

COLD CANADIAN AIR ARRIVES IN EARNEST THIS AFTERNOON. TEMPERATURES
ARE FORECAST TO FALL BELOW 32 DEGREES TONIGHT...ESPECIALLY IN RURAL
AND OUTLYING AREAS. PRECAUTIONS SHOULD BE TAKEN TO PROTECT TENDER
VEGETATION. THIS IS THE FIRST OF WHAT COULD BE A SERIES OF FREEZE
WARNINGS THROUGH THE WEEKEND...AS COLD AIR PAYS AN EXTENDED VISIT.

A FREEZE WARNING MEANS SUB-FREEZING TEMPERATURES ARE IMMINENT OR
HIGHLY LIKELY. THESE CONDITIONS WILL KILL CROPS AND OTHER
SENSITIVE VEGETATION”

Status of Grape Hardiness and Frost Protection Considerations
By: Imed Dami and Anton Prajitna, HCS-OARDC
 

 
 

-         A freeze test of varieties grown at the OARDC vineyard in Wooster was conducted on 29 March by Anton Prajitna, Viticulture Research Assistant, to check their cold hardiness status. The following are the critical temperatures (CT) that caused 50% bud damage or LT50 (buds were still dormant when collected):
o       Seyval ---- 9.6F
o       Vidal ---- 8.7F
o       Pinot gris ----7.4F
o       Chambourcin ----6.7F
o       Concord ---- 6.1F
o       Traminette ---- 5.1F
-         CT varies with the region where grapes are grown in the state. The above varieties grown in Wooster are still “dormant” and not at the swollen stage yet.  This is not the case for vineyards in southern and central Ohio where bud break and shoot development has already occurred in early varieties. In other words, varieties in the south are about 2 to 3 weeks ahead in growth than the varieties in the north.  Therefore, bud hardiness of varieties in the south is lower (5F or more) than those reported above. Varieties grown by Lake Erie will be the least developed and thus most hardy (coolest region in the state). 
-         During deacclimation, grapevines become increasingly sensitive to temperature below freezing (32F) and CT varies with the stage of bud development. That is, buds become more sensitive as they grow in early spring. The following is an example of critical temperatures that cause 50% damage of grape buds and young shoots:
o       Swollen bud stage ---- 26F
o       Bud burst (break) ---- 28F
o       First unfolded leaf ---- 28F
o       Second unfolded leaf ---- 29F
o       Fourth unfolded leaf ---- 30F
-         CT also varies with weather conditions including air relative humidity and corresponding dew point. Dew point (DP) is the temperature at which water condenses out of the air as dew or the temperature that corresponds to 100% relative humidity.  Condensation releases heat and slows the drop of air temperature. Thus, if DP is higher than CT, heat will be released before reaching damaging temperatures and may provide some protection.  If the air is dry, DP is low and temperature will drop rapidly and may reach CT and thus cause more damage.
 
What to Do?
-         Last year, I gave a presentation on frost protection of grapevines at the Ohio Grape-Wine Short Course. The PPT was provided to all registrants in a CD. Please let me know if you’d like a copy. At this point in time, here are suggestions that may help with minimizing damage:
-         Delay or stop the entire pruning operation of vinifera varieties.
-         Assess bud damage (see previous OGEN issue)
-         Double-prune: prune generously leaving 2x to 3x the amount of target bud number. With spur pruning, leave longer spurs. This practice will delay bud break of basal buds. After the frost threat in your area has passed, conduct a second pruning after shoot growth and retain the final target bud number.
-         If you have wind machines, plan to use them under these conditions. At these predicted low temperatures, you may not only protect buds, but potentially the permanent structure of vines (e.g. trunks).
-         Spraying soybean oil now is late to cause a significant delay of bud break and provide frost protection. I would not recommend it at this time of the year.
-         Do not spray your vineyard with water!! Spraying water is not equivalent to sprinkler protection. Actually, rather than protecting, spraying water would cause even more bud damage.
-         Use of heaters can also be beneficial, but I am not aware of grape growers in Ohio using heaters in their vineyards.
-         Let’s hope Mother Nature cooperates and the forecast is not as “gloomy”!

Pest Awareness at Bud Swell
By: Roger Williams and Dan Fickle, Entomology-OARDC

           
            Spring is here at last and its time once again to be on the lookout for the first pest of the season; the grape flea beetle.  This beetle is about a ¼ inch in length, metallic steel blue in color and can be easily spotted on grape canes and buds on warm sunny days.  If flea beetles are present in sufficient numbers when the vines are in the bud swell stage they can inflict severe damage to the newly forming swollen buds. 
 
Scouting of the vineyard for adult flea beetles should begin at bud swell and continue until bud development is past the critical stage, approximately ¾ inch growth. 
Scouting should be conducted along the vineyard perimeter and near the center of the vineyard.  Areas adjacent to wood lots are of particular concern.  At least 25 vines should be examined at each of the five locations.  Buds should be closely examined for signs of flea beetle feeding.  If bud damage (holes eaten in the buds) is 4% or greater an application of insecticide should be applied.  Remember if emergence of this pest coincides with bud swell extensive damage to fruit development may result.  Once the vines are past bud swell direct damage to the developing fruit is no longer of major concern however, adult beetles and developing larvae will feed on foliage causing holes and frayed areas in the young leaves.  This damage is usually not of major concern but may lead to a build up in the flea beetle population from one year to the next and therefore treatment may help to prevent populations in subsequent years from reaching damaging numbers.  This pest can be easily controlled with the insecticide; Danitol or Sevin.
 
Got A Pest Problem?
By: Roger Williams and Dan Fickle, Entomology-OARDC
 
http://www.oardc.ohio-state.edu/grapeipm/
 
Check out the new grape IPM web site, “Insects and Mite Pests of Grapes in Ohio and the Midwest” a complete listing of insect and mite pests, color photos, damage symptoms, scouting information, management and control strategies, links to pesticide recommendations and other related web pages.  We will be routinely updating this web site so that the latest pest information is available to our growers.  Comments or suggestions welcomed.
 
williams.14@osu.edu
fickle.1@osu.edu
 


Welcome to New Members in the Viticulture and Enology Program
 
Taehyun Ji (TJ) joined the Viticulture and Enology Program as a Research Associate in the department of Horticulture and Crop Science at the Ohio State University in 2005.  Dr. Ji has more than 12 years of research experience in the field of food, flavor, and analytical chemistry. His research focuses on the enhancement of fruit and wine quality, specifically aromatic and flavor compounds in grapes and its products in relation to climatic conditions and cultural practices. Since joining the program, Dr. Ji assisted with flavor and wine analysis in grapes and wines including resveratrol. He has also developed a new method to extract and analyze volatile aromatic compounds in a number of white grape varieties including Traminette. He has also assisted Dr. Imed Dami with developing a new method to analyze specific sugars that impart cold hardiness to grapevines. He’s housed at the OARDC campus in Wooster, OH.
 
Anton Prajitna joined the Viticulture Program as a Research Associate in the department of Horticulture and Crop Science at the Ohio State University in November 2006. Anton has a Master’s degree in horticulture and his thesis focused on fruit and wine quality manipulation in the vineyard. Specifically, he studied the effect of cluster thinning on polyphenolics and health benefits in red grape varieties grown in Ohio. He will be maintaining vineyard research plots at OARDC, and coordinate and conduct field experiments in research and commercial vineyards. He is also housed at the OARDC campus in Wooster.