Vineyard IPM Scouting Report for week of 19 July 2010 UW-Extension Door County and Peninsular Agricultural Research Station. in Sturgeon Bay, WI

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1 Vineyard IPM Scouting Report for week of 19 July 010 UW-Extension Door County and Peninsular Agricultural Research Station Sturgeon Bay, WI Grape Phylloxera FAQ What is phylloxera? There are two forms of phylloxera based on the life cycle of the pest with one form feeding within root galls and the other feeding within leaf galls. In Wisconsin, the leaf gall form of phylloxera predominates, this is likely do to the fact that Vitis species of American heritage are resistant to the root form. Will phylloxera kill grapevines? Heavy infestations that result in a lot of leaf galls will reduce photosynthesis and therefore reduce sugar production that may play an indirect role in winter hardiness especially in young vines. What is the threshold for phylloxera? No thresholds have been established. Does applying a insecticide after galls first appear reduce further gall formation? Phylloxera has multiple generations per year, nymphs or crawlers will exit the galls on the older leaves and move to the shoot tips resulting in more galling. Once crawlers are within galls, most insecticides are ineffective. Will phylloxera reduce yield? Only if severe galling results in more than 70% of the leaves infected. Phylloxera impacts fruit production the greatest if severe galling occurs weeks post-bloom. Are some French American hybrids more susceptible to phylloxera than others? Frontenac has been most severely infested by phylloxera in the vineyards I have scouted the previous 4 years. When is the best time to manage phylloxera? Early season control is critical and insecticides should be applied during bloom. Where can I get information on insecticides to manage phylloxera? See page 5 of the 010 Midwest Small Fruit and Grape Spray Guide at Grape Phylloxera galls appeared on wild grapes this week at the Peninsular Research Station in Sturgeon Bay, WI 1

2 What s lurking in or near the vineyard this week? Downy mildew lesions or oil spots on the top of leaf (left) and the white downy spore masses on the bottom of the leaf. Phylloxera galls on top of leaf Grape Phylloxera appeared for the first time this season on wild grapes at PARS. Even though the grape crop and degree days are much farther progressed this year compared to last, phylloxera appeared two weeks latter this year on wild grapes than last year. Phylloxera galls on bottom of leaf

3 3 Development of wine grapes at the Peninsular Agricultural Research Station (PARS) Sturgeon Bay, WI and the West Madison Agricultural Research Station (WMARS), Madison, WI. Buds damaged by frost at PARS on 5/8 and 5/9/ Brianna at PARS Brianna at WMARS Foch at PARS Foch at WMARS La Crescent at PARS La Crescent at WMARS New buds selected at PARS this week for following phenology since buds featured in previous issue (week of ) of the IPM report were damaged by frost.

4 4 Development of wine grapes at the Peninsular Agricultural Research Station (PARS) Sturgeon Bay, WI and the West Madison Agricultural Research Station (WMARS), Madison, WI. Buds damaged by frost at PARS on 5/8 and 5/9/ La Crosse at PARS La Crosse at WMARS Marquette at PARS Marquette at WMARS Wild grape at PARS New buds selected at PARS this week for following phenology since buds featured in previous issue (week of ) of the IPM report were damaged by frost.

5 5 Degree Day 1 (base 50) Accumulation since April 1, 010 at Peninsular Agricultural Research Station in Sturgeon Bay, WI Date Year Average 7/18/ Average from 005 to 009. Degree Day 1 (base 50) Accumulation since April 1, 010 at West Madison Agricultural Research Station, Madison, WI Date Year Average 7/18// Average from 006 to 009. Accumulated degree days 1 (base 50) for the month of March at Peninsular Agricultural Research Station. Year Degree days (base 50) Low temperatures reported at Peninsular Agricultural Research Station, Sturgeon Bay, WI. Date Low F 5/3/ /4/ /5/ /6/ /7/ /8/ /9/ Frost damage reported to some grape varieties in grape variety trial. Please scout your vineyards on a regularly scheduled basis in an effort to manage problem pests. This report contains information on scouting reports from specific locations and may not reflect pest problems in your vineyard. If you would like more information on IPM in grapes, please contact Dean Volenberg at (90) or dean.volenberg@ces.uwex.edu