By Henry Wu, Technical Sales Support Representative, Chemtura AgroSolutions
As new products keep hitting the market, determining the right chemical combination to control key diseases in the vineyard can seem overwhelming. Focusing on the core chemical attributes of fungicides can help you navigate the expanding world of chemical disease control options.
Selecting the right fungicide for a vineyard starts by understanding the unique characteristics of the individual product’s chemistry. The three most commonly used groups of grape fungicides are sterol inhibitors (known as SIs and also DMIs), strobilurins and inorganics. Other classes of chemistries include quinolines (quinoxyfen) and carbamates (mancozeb). Each of these chemical groups has an important niche in a grape disease control program. Playing to the strengths of the different materials in your arsenal helps you get the best results.
Sterol inhibitors, such as Viticure fungicide, work by inhibiting development of cell walls in the target organism. Without cell walls, the organism cannot survive. This type of chemistry is especially active against powdery mildew and can be applied in rotation throughout the season. Some SIs also control additional diseases. For example, in addition to powdery mildew control, Viticure is labeled for suppression of black rot and Botrytis bunch rot.
Strobilurins, including pyraclostrobin and trifloxystrobin,interfere with energy production and cell respiration to prevent spore germination in fungi. Applying strobilurins later in the season during bunch development not only supports a powdery mildew control program, but also helps prevent Botrytis bunch rot and grey mold.
Inorganic compounds, such as copper and sulfur, prevent fungi from attaching to plant surfaces. Fungi do not develop resistance to this type of material, making inorganic compounds an effective preventative tool as well as a key component of resistance management in the vineyard. Most spray programs start with an application of sulfur at bud break and intersperse additional applications between strobilurin and sterol inhibitor applications during the growing season.
When organizing a spray program, I recommend growers start with sulfur, then use an SI, come back to sulfur, switch to a strobilurin, and then use sulfur again before applying an SI product. Rotating among SIs, strobilurins and inorganic compounds during the growing season brings the benefits of each chemical group together, delivering effective disease control while managing resistance development.