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Vine Lines: Managing Powdery Mildew
by Ron Brase
The chart below indicates variety susceptibility to powdery mildew.
| Susceptibility |
Vinifera Winegrape Varieties |
| High |
Carignane, Chardonnay, Chenin blanc, Muscat blanc (Canelli), Roussane |
| Moderate |
Barbera, Burger, Cab franc, Cab Sauvignon, Gamey Beaujolais, Grenache, Malbec, Melon, Mission, Muscat noir, Nebbiolo, Pinot noir, Ruby Cabernet, Sauvignon blanc, Semillon, Syrah, Tempranillo, Viognier, Zinfandel |
| Low |
Alicante Bouschet, Dolcetto (Charbono), Folle blanc, French Colombard, Gewurztraminer, Malvasia Bianca, Merlot, Mourvedre, Palomino, Petite Sirah, Riesling, Sangiovese, Ugni blanc, Valdiguie (Napa Gamay) |
| Slight |
Trousseau (Grey Riesling), Rubired |
The chart below indicates powdery mildew materials and the treatment intervals noted in their labels for grapes. This should not be considered a complete list of all materials available and is not an endorsement of specific materials. However, it does include most of the commonly used materials. Growers should consult their Pest Control Advisor for the best material choices.
| Materials |
Treatment Intervals |
| Preventatives: |
|
| Sulfurs & Related Materials: |
|
| Dusting Sulfurs |
7-14 days |
| Wettable & Micronized Sulfurs |
7-14 days |
| Sulforix® |
7-14 days |
| Other Preventives: |
|
| Quinec® |
7-21 days |
| Contacts: |
|
| Bicarbonates: |
|
| Armicarb 100® |
5-14 days |
| Kaligreen® |
7-10 days |
| Oils: |
|
| Stylet® |
7-14 days |
| M-Pede® (fatty acid) |
7-14 days |
| Trilogy® (Neem oil) |
7-10 days |
| ERase® (Jojoba oil) |
7-14 days |
| Biofungicides: |
|
| AQ-10® |
10-14 days |
| Serenade® (Bacillus subtillus) |
7-10 days |
| Sonata® (Bacillus pumilis) |
7-10 days |
| Sterol Inhibitors (EBI’s & DMI’s): |
|
| Elite® |
14-21 days |
| Procure® |
14-21 days |
| Rally® |
14-21 days |
| Rubigan® |
14-18 days |
| Strobilunines (systemic): |
|
| Abound® |
10-14 days |
| Abound® |
10-14 days |
| Flint® |
14-21 days |
| Sovran® |
14-21 days |
| Pristine® |
14-21 days |
| SAR (Systemic Activated Resistance): |
|
| Auxigro® |
14-21 days |
| Elexa® |
14 days |
| Messenger® |
14 days |
X Marks The Spot: Bacterial spot (Xanthomonas arboricola) can cause serious damage to stone fruit.
By David Ritchie
The chart below is an example of a spray program for highly susceptible peach cultivars in orchards where bacterial spot is a problem. For less susceptible cultivars, but where bacterial spot occurs, only the first two to three sprays may be needed with use of additional sprays depending on disease occurrence and weather conditions. Always examine the foliage on trees for unacceptable copper injury before making the next copper application. This is especially important for applications at shuck split and later. If unacceptable injury is present, reduce rate of copper or switch to oxytetracycline.
| Application Time |
Material* and Rate Per Acre |
| Late dormant to early bud-break |
2.0 to 3.0 lb metallic copper equivalent** |
| Pink-bud but before blossoms open |
1.0 to 1.5 lb metallic copper equivalent ** |
| Up to 5% blossoms open |
0.75 to 1.0 lb metallic copper equivalent ** |
| 50 to 75% petal-fall with less than 1% shuck-split |
0.25 to 0.50 lb metallic copper equivalent ** |
| Shuck-split to 25% shucks off |
0.125 lb to 0.25 lb metallic copper equivalent ** OR oxytetracycline (Mycoshield 17W or FlameOut 17W 0.75 to 1.25 lb) |
| 7 to 14 days later |
Mycoshield 17W or FlameOut 17W 0.75 to 1.25 lb |
| Additional sprays at 7 to 14 intervals depending upon frequency of precipitation and disease pressure |
Mycoshield 17W or FlameOut 17W 0.75 to 1.25 lb OR Alternate low rates of copper [0.031 lb (0.5 oz) to 0.125 lb (2.0 oz) ] with oxytetracycline OR Tank-mix of copper with oxytetracycline |
*Before use, growers should always check the pesticide label. Also check with local authorities (eg, Cooperative Extension Service) that materials are registered and how best to use them in their area.
** There are many formulations containing different concentrations of metallic copper. The metallic copper concentration usually is stated on the label as the % metallic copper equivalent (M.C.E.). The above rates are based on the M.C.E., NOT on what is stated as “active ingredient”. For example: if 1.0 lb of M.C.E. is recommended and the product label states M.C.E. is 40%, divide 1.0 lb by 0.40, this equals 2.5 lb of product.
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