Vineyard IPM Scouting Report for week of 15 July 2013 UW-Extension Door County and Peninsular Agricultural Research Station

Transcription

1 NO Vineyard IPM Scouting Report for week of 15 July 2013 UW-Extension Door County and Peninsular Agricultural Research Station Rupestris Speckle and Muscat Spot Patty McManus, UW-Madison Plant Pathology and UW-Extension Rupestris speckle (Figs. 1 and 2) is a physiological disorder that affects certain varieties of grape with Vitis rupestris in their heritage. On the variety Valvin Muscat, rupestris speckle is sometimes called muscat spot (Fig. 2). The symptoms can be confused with various diseases, and they can look different on different cultivars. The precise cause of this disorder is not known, but it is apparently related to stress that leads to low vigor. Symptoms are more common on older leaves. No control measures are recommended, as this appears to be an insignificant problem, except for the confusion it causes. At the West Madison Agricultural Research Station (WMARS) we are seeing a lot of rupestris speckle on Frontenac and Frontenac Gris (Fig. 1) in a planting established 2012, while the other varieties in that planting Brianna, LaCrescent, LaCrosse, Marquette, St. Croix, and Valiant do not have speckling. In a planting established in 2008 at WMARS, we are seeing very minor speckling on Vignoles and Frontenac and moderate symptoms on Valvin Muscat (Fig. 2). The spots are much larger on Valvin Muscat than Frontenac and Vignoles, but are believed to be insignificant to the health of the vine. Berries appear normal in all cases. Although called rupestris speckle, the severity of this disorder does not appear to be precisely correlated with the amount of V. rupestris in the variety s makeup. Other varieties in the 2008 planting that are NOT showing symptoms are Brianna, LaCrescent, LaCrosse, Leon Millot, Marquette, MN1220, NY76, and Petite Pearl. Figure 1. Rupestris speckle on Frontenac Gris planted in 2012 at WMARS. Speckling ranges from minor (left) to severe (right).

2 2 Figure 2. Rupestris speckle is sometimes called muscat spot when it occurs on Valvin Muscat, as in the case at WMARS. A Few Notes From Dean on Rupestris speckle. The Rupestris speckle seems to be widespread this year and I have received pictures from other growers that suspected a black rot infection (Figure 1 on right). Some of the larger lesions on the leaves appear to be black rot, but it is difficult to diagnose with pictures only. If you suspect a black rot infection, examine the lesions with a hand lens to see if small black fruiting bodies are present. These fruiting bodies will be in a ring on the outer margin of the lesions. What was particularly apparent from the pictures was that something other than black rot was present. The leaves are speckled and this speckling is the result of Rupestris speckle (see the article by Patty McManus). Figure 1. Rupestris speckle and what appears to be a few black rot lesions on Frontenac.

3 WHAT IS LURKING IN AND AROUND THE VINEYARDS 3 A Downy mildew on wild grape. Top side of leaf showing the lesions (A) and the bottom of the leaf showing the downy mass (B). B Grape tomato galls on wild grapes at PARS (left). Gramoxone herbicide injury to grape leaf.

4 Development of wine grapes in the grape variety trials at the Peninsular Agricultural Research Station (PARS) Sturgeon Bay, WI and West Madison Agricultural Research Station (WMARS), Madison, WI 4 Brianna at PARS Brianna at WMARS Foch at PARS Foch at WMARS Frontenac at PARS Frontenac at WMARS

5 Development of wine grapes in the grape variety trials at the Peninsular Agricultural Research Station (PARS) Sturgeon Bay, WI and West Madison Agricultural Research Station (WMARS), Madison, WI 5 La Crescent at PARS La Crescent at WMARS La Crosse at PARS La Crosse at WMARS Marquette at PARS Marquette at WMARS

6 6 Grape progress update of other varieties in the grape variety trial located at the Peninsular Agricultural Research Station. NY76 at PARS Leon Millot at PARS Petite Pearl at PARS Frontenac gris at PARS Vignoles at PARS Noiret at PARS

7 7 Grape progress update of other varieties in the grape variety trial located at the Peninsular Agricultural Research Station. Pristine phytotoxicity MN 1200 at PARS MN 1258 at PARS MN 1220 at PARS MN 1200 at PARS

8 8 Degree Day 1 (base 50) Accumulation from April 1 to July 14, 2013 at Peninsular Agricultural Research Station in Sturgeon Bay, WI Date Year Average 2 4/1 to 7/ Modified method. 2 Average from 2008 to Degree Day 1 (base 50) Accumulation from April 1 to July 14, 2013 at West Madison Date Year Average 2 4/1 to 7/ Modified method. 2 Average from 2008 to Accumulated degree days 1 (base 50) for the month of March in Sturgeon Bay and Madison, WI. Year Madison WI Sturgeon Bay WI Modified method. 2 Data from GDD (base 50, ceiling 86) 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 (920) or dean.volenberg@ces.uwex.edu