April showers can bring more than a rainbow to a grape grower’s vineyard: sometimes it can bring deadly diseases such as Botrytis bunch rot and powdery mildew.
High-humidity conditions, paired with elevated nitrogen levels and cluster compactness, can promote a Botrytis outbreak. Infections are most severe when relative humidity exceeds 92 percent, free moisture is present on the fruit surface and temperatures are in the 58 to 82°F range, states UC IPM. Grapes in condensed clusters can crack due to pressure, creating ideal entry points for fungus as well as a moist habitat for the spores to germinate. Making matters worse, ripe berries can attract fruit flies, which help spread Botrytis on their bodies from plant to plant.
Along with Botrytis, powdery mildew thrives in similar high-humidity and cool spring climates. The fungal infection settles on the surface of plant tissue and occupies the top layers of epidermis cells. Invasion of this disease can cause substantial damage to plant growth, crop yield and fruit quality. The disease requires season-long maintenance because of early season inoculum and secondary infection caused by fungal spores that can infect, develop new spores and re-infect throughout summer months. Secondary infection cycles can occur approximately every five to 30 days, depending on the weather.
PH-D® is a broad-spectrum fungicide that offers a high degree of Botrytis and powdery mildew control in grapes. Its benefit of a 0-day pre-harvest interval and 4-hour REI make it an excellent option for disease management sprays close to harvest. PH-D is the only product in FRAC Group 19, making it an important resistance management tool. The formulation is fast-acting with superior mixability that goes easy on beneficials. It can be applied to grapes when climatic conditions exist for the development of Botrytis and powdery mildew.
"PH-D is a trusted fungicide offering effective control with a unique mode of action that has become an important resistance management tool for tough diseases in grapes, in addition to other key California crops,” said Karen Westcott, U.S. Specialty Crops Fungicides, UPL. “PH-D is a good option if you’re looking for a fungicide to cover key diseases in grapes. Two important treatments are at bunch closure and pre-harvest, in order to take advantage of the product’s favorable pre-harvest interval.”
Growers saw great success with their applications of the product. Brett Ploszaj and Kevin Hodges of Crop Production Services put their trust in PH-D Fungicide for powdery mildew that’s hard to get rid of. Here’s what they had to say:
“PH-D gave a 75-80 percent reduction in the powdery mildew. Hands down the best powdery mildew knockback I have ever seen,” said Ploszaj of Madera, California.
Hodges of Fresno, California, agreed. “PH-D did a good job of knocking the powdery mildew back. The powdery mildew did come back in the heaviest spot, but 95 percent of the block was cleaned up with the PH-D,” he said.
UPL recommends that growers apply PH-D at the crop stage indicated on the product label for each crop and then rotate to fungicides with other modes of action as part of their resistance management strategies. The product label can be found here.
No matter the disease pressure, you can count on UPL for premium solutions to help keep your vineyard running strong. For more information, contact your local UPL sales representative or visit www.upl-ltd.com/us.
