'musc-mg' ~ electronic advisory from NC Cooperative Extension Service for muscadine growers
Vol. 5 No. 1
June 22, 2009

Contributors to this advisory:
Connie Fisk, Muscadine Extension Associate – Muscadine Grapes, Dept. of Horticultural Science, NCSU
Bill Cline, Extension Plant Pathologist, Dept. of Plant Pathology, NCSU

Topics in this issue:
*Muscadine Disease Update
*Japanese Beetles Have Arrived
*Herbicide Injury Symptoms in Muscadines
*Vineyard Chores
*Upcoming Events

Muscadine Disease Update

Wetter-than-normal weather has resulted in some severe outbreaks of leaf spots caused by the black rot fungus (right), as well as early appearance of angular leaf spot (far right).  Both of these fungal diseases are common on muscadines in NC, but usually are not quite this severe.  Other diseases that may require fungicidal sprays in the coming weeks include powdery mildew and fruit rots.  Research at Castle Hayne has shown that sprays from prebloom through July are the most effective in controlling powdery mildew and are also highly beneficial in preventing fruit rots at harvest.  For complete spray recommendations, see under "muscadine spray program" the NC Ag Chemicals Manual Chapter VII, Insect and Disease Control of Fruits:  http://ipm.ncsu.edu/agchem/7-toc.pdf

Some growers have had difficulty sourcing the fungicide Nova in 2009.  There is a reason for that!  Thanks to Kathryn Holmes, agent in Rockingham Co., for discovering that Nova is no longer the trade name for myclobutanil as labeled for grapes in the US.  The currently-available product, Rally, uses the same active ingredient at the same concentration, just with a different trade name.  At one time, sale of myclobutanil under the Rally trade name was limited to certain states in the western US, and Nova was used as a trade name elsewhere.  However, since 2007 the Rally trade name is used nationwide.  (See the label for Rally here.)

Japanese Beetles Have Arrived

I saw my first Japanese beetle of the year on June 9.  As you probably know, Japanese beetles emerge once a year and feed on the foliage of ornamental and crop plants.  They are especially troublesome in vineyards that used to be pastures.  Fortunately, muscadines produce copious amounts of leaves so unless the beetles are eating every leaf off your vine (as in during establishment), you can probably tolerate some Japanese beetle damage.  There are pheromone traps available for Japanese beetles but the thing to remember is that the pheromone attracts Japanese beetles, so don’t hang these traps in your vineyard!  If you determine that you must spray something for them consult the Southeast Regional Muscadine Grape Integrated Management Guide at http://www.smallfruits.org/SmallFruitsRegGuide/.  For more information on the biology and management of adult Japanese beetles, consult the insect note at http://www.ces.ncsu.edu/depts/ent/notes/O&T/flowers/note44/note44.html.

Herbicide Injury Symptoms in Muscadines

Every year we receive calls about distorted leaves in muscadine vineyards with the common culprit being herbicide injury, and this year is no exception.  In fact this year has given us some of the most dramatic herbicide injury I’ve seen in my three years working with muscadines.  Grapes are very sensitive to 2,4-D – so sensitive that new leaves emerging a half mile away may curl up and demonstrate what is called strapping (see photo at right).  Do not apply 2,4-D-containing products to your vineyard.  I also encourage you to discuss this sensitivity with your neighbors.  Depending on the extent of the damage you may only see leaf symptoms or the vine may be temporarily stunted.  Fortunately in most cases the vines will grow out of the damage.

We also had a call this season about muscadine leaf whitening.  The vineyard was next to a tobacco field
where Command had been applied (see photo at right, courtesy Robeson County Extension Agent Jeff Floyd).  Command is used to control broadleaf weeds and grasses but the off-site movement of spray-drift or vapors can damage nearby fruit crops.  Command will cause leaf yellowing or whitening and should not be sprayed within 1200 feet of grapes.  Command may stunt current season's growth and reduce yield, but new emerging growth should look normal.  New growth should begin within 2-4 weeks of the herbicide application.  In general, older vines will be more tolerant of herbicide spray drift. What you may see as a result of the injury (depending on the dose) will be a delay in bloom as well as uneven ripening.  The vineyard should be fine in the long run.

Vineyard Chores

*Maintain your fungicide spray program (see Muscadine Disease Update above).
*Keep up with vineyard training – with all the rain we’ve had lately there’s a lot of new growth and we want to direct the vine’s energy down the wire.
*If you have troublesome vineyard weeds you do have management options.  Consult page 25 of the Southeast Regional Muscadine Grape Integrated Management Guide at http://www.smallfruits.org/SmallFruitsRegGuide to choose what to spray based on vine age.
*Remember to order or propagate vines for next year now, while the shoots are actively growing.
*Get your last dose of fertilizer out (if needed) before the first weekend in July.

Upcoming Events

*NC Muscadine Grape Association Bus Tour Friday August 7 – look for a promotional flier in your mailbox this week or visit http://www.ncmuscadine.org for complete details
*NC Muscadine Festival Saturday September 26 – visit http://www.muscadineharvestfestival.com for details

For general muscadine grape information for North Carolina visit http://www.ces.ncsu.edu/muscadines

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