North Carolina Winegrowers Presentation and Handouts

I will be presenting at the NC Winegrowers Association's annual meeting in Greensboro, NC tomorrow morning. I'll be speaking about grape root borer (a growing concern in NC vineyards), spider mites (a potential pest), grape phylloxera (an emerging issue for hybrid grapes), harvest season insects, and our newest invasive species. I will also be discussing insect monitoring and suggested sampling programs.

Handouts for my talk as well as the slides from my presentation are linked below. As always, information presented about pesticides is intended for North Carolina growers and is subject to change. Always read and follow the pesticide label and see "a note on pesticide recommendations".

More information

North Carolina Winegrowers Association presentation - February 6, 2011

Example sampling program for NC winegrapes

Insecticides registered for use in grapes & their potential use against SWD

Grape phylloxera update

Grape phylloxera adults and eggs in foliar galls at RayLen Vineyard. Photo: HJB

Last Thursday I visited RayLen Vineyard to see the grape phylloxera (Daktulosphaira vitifoliae) infestation I posted about previously.  In person, the extent of the damage was even more impressive.  The Vidal Blanc vines were nearly completely infested.  This suggests that several generations have cycled through during this summer.  Vidal is a French-American hybrid grape.  Hybrids (ie. Traminette, Seyval Blanc, Chambourcin) are increasing in popularity among eastern grape growers because they are often more tolerant of our weather conditions that European varietals (ie. Merlot, Chardonnay, Cabernet Sauvignon).  However, it appears that some of these hybrids are more susceptible to foliar phylloxera.  Because they are grown on phylloxera tolerant rootstock, it is unlikely that phylloxera are also damaging roots.

Infested Vidal vines. Photo: HJB

Leaves at the base of the canes had no live phylloxera present.  I started to find live phylloxera about half way up the canes, and the youngest leaves had females and eggs in the galls as well as few crawlers.  

Mature grape phylloxera female and eggs (indicated by red arrow) and crawler (blue arrow) on a young grape leaf.  Photo: HJB

Donn Johnson, University of Arkansas small fruit entomologist, has posted several other images of eggs, crawlers and adults here.  The leaves with active infestations were near the end of canes and likely to be removed during hedging (which was planned for the next few days after my visit to RayLen), and because of this, I was reluctant to recommend a pesticide application.  Instead, I suggested removing as many infested leaves as possible during hedging/leaf removal and destroying them.  They could then follow this up with a pesticide treatment if crawlers or open galls (see below) were still present.  

Open galls on young leaves.  The insects in these galls are susceptible to contact insecticides.  Photo: HJB

It seems likely that phylloxera will continue to be a problem in French-American hybird grapes, which I am still a fan of for their many other good qualities.  The strategy at RayLen and other infested vineyards should include early season scouting for first generation phylloxera--likely to be a few galls near the base of cane in spring.  Once crawlers of this first generation appear, foliar treatments should be applied (some of the materials available for phylloxera management are listed in this University of Arkansas fact sheet). Regular scouting for subsequent generations should be conducted throughout the summer followed by treatment as they appear.  Severe phylloxera infestations weaken vines and leave them more susceptible to winter injury.

Phylloxera infested cane.  Photo: HJB

Grape phylloxera in NC vineyards

Vidal Blanc grape leaves heavily infested with the foliar form of grape phylloxera at RayLen Vineyards, Mocksville, NC.  Photo: Turner Sutton

This Wednesday, I received an email from Steve Shepard, vintner at RayLen Vineyards, describing a large infestation of the foliar form of grape phylloxera in his Vidal Blanc block.  Vidal Blanc (or just Vidal) is a French hybrid grape widely planted in the eastern US because of its cold tolerance.  I made plans to visit the vineyard next week and was not too concerned about the potential for damage.  Then I received an email from Turner Sutton, NC State plant pathologist, who sent me a photo of the damage (above).

Grape phylloxera (Daktulosphaira vitifoliae) is an aphid like insect which can feed on both leaves and roots of grape vines. Foliar infestations of grape phylloxera are fairly common in NC, but they are usually limited to a few galled leaves and do not impact photosynthesis.  If only a few galls are present, removing the affected leaves before the galls spread can limit an infestation.  In fact, phylloxera was of so little concern last year that we did not address its management in the Southern Region Small Fruit Consortium Bunch Grape IPM Guide. We are meeting to edit this guide in 3 weeks, and adding phylloxera will on the top of my list of changes.  The root feeding form of phylloxera has received most of the attention as a pest because of its potential damage to western US grape plantings and its history as an invasive species in France.  Native North American grapes are naturally tolerant to root feeding by phylloxera, but native French varieties were not.  The use of American root stocks grafted to French varieties (developed by pioneering American entomologist Charles Valentine Riley) is credited with saving the French wine industry.

Foliar phylloxera has become increasingly common in recent years, and infestations as severe as the one at RayLen can reduce photosynthesis therefore decrease fruit quality and vine vigor.   French-American hybrid grapes are being planted more frequently in the eastern US because of their tolerance to varying climatic conditions, but many of these varieties appear more susceptible to foliar phylloxera.  The grape phylloxera life cycle is very complicated, but the stage most amenable to management are the crawlers, which move on the plant surface to found new galls.  Not all the galls on the leaves in Turner's photo necessarily contain live phylloxera, as the galls will remain after the insects have moved on.

Comparatively little work has been done on foliar phylloxera, but Dr. Donn Johnson at the University of Arkansas has put together an excellent fact sheet on phylloxera biology and management.  Dr. Johnson also works with Missouri wine growers, who have been dealing with damaging foliar phylloxera infestations for several years.

More information
Biology and management of grape phylloxera - Johnson, Sleezer, and Lewis