Manage Copper Fungicides
July 24, 2013 Editor’s Note: This article was submitted by Sage Virtual Communications on behalf of MANA (Makhteshim Agan of North America, Inc., a North American subsidiary of Makhteshim Agan Industries, Ltd.)
Copper-based fungicides have become a staple against high-value crop losses caused by bacterial and fungal diseases. While considered irreplaceable by growers as a preventive disease-management tool, copper inputs are known for being difficult crop protection inputs to manage.
Today’s copper fungicides are more active, which in the practical sense means less copper is actually applied to crops and soils. However, not all copper fungicide products are created equal as indicated by the differences in the percent of active ingredient and the formulation of copper used.
Herb Young, MANA brand leader, says the difference between copper-based fungicides comes down to the balance between particle size and formulation.
“Product performance in disease control has improved with new entries like copper hydroxide, which has helped growers move beyond ‘old school’ inputs,” said Young. “Currently, the industry is focused on research and development that helps improve copper formulations in regard to handling, mixing, and suspension properties.”
To explain Young’s comments, users of conventional copper fungicides are regularly burdened by visible “bluish” plant residue, settling out of material in spray tanks, nozzle clogging and equipment corrosion, and soil loading.
While proven for high-quality disease control, Young believes “the missing link” has been the availability of advanced formulations or delivery systems that help growers overcome the downsides of copper inputs.
Copper: Effective But Challenging
The majority of copper fungicides used today are formulated as wettable powders, flowables, water-dispersible granules, or water-soluble packets.
Dr. Kelly Ivors, Extension plant pathologist with North Carolina State University, said many types of copper products require constant agitation to maintain suspension, which increases time and attention to get optimal performance.
“While copper is an important plant protectant, especially for foliar bacterial diseases on tomatoes and pepper, it does require more attention in detail and precision to get even coverage on plant foliage across a field.”
Based on the amount of time and money that growers put into producing a quality crop, Ivors said there is little to no room for margin of error when applying copper fungicides.
Gary Cloud, certified crop advisor and owner of GLC Consulting in Tallahassee, FL, knows all too well about the challenges aligned with copper-based fungicides.
“Aggressive mixing is absolutely essential. If a copper mixture sits in the tank even for short periods of time, it falls out of suspension,” he said. “Once a product settles to the bottom of the tank, there’s always a risk of not being able to get the mixture back into suspension. Making matters worse is when a poorly suspended treatment goes out across a field. The application is either uneven, or you take on the risk of having little to no copper applied because the active ingredient is sitting at the bottom of the tank.”
Cloud adds that application and tank mix mishaps can put plants in a vulnerable position if the outgoing compound is not suspended properly.
Sarah Hornsby, president of Agricultural Crop Consulting, Inc., in Parrish, FL, concurs with Cloud while calling attention to the headaches of clogging and “caking” on sprayer equipment.
“It’s not uncommon to get clumping and settling with conventional copper fungicides,” she said. “For anyone who has ever used these inputs, sprayer issues are the norm. We often have to stop our sprayers and clean the systems out. Plus, the abrasion and corrosion caused by copper fungicides puts a lot of wear and tear on equipment, which adds time and expense.”
Powdered or granulated copper fungicides pose additional challenges for Hornsby. “With a solid formulation, you get flashback or dust whenever emptying the product into the mixing tank,” she said. “This is another issue that we’re concerned about specific to applicator safety.”
Battling The Blue
Copper sulfate, or bluestone, was one of the first forms of copper used as a fungicide. Today, there are a variety of “fixed” copper sources available, as well as Bordeaux mixtures, which combine traditional copper sulfate with lime (calcium hydroxide). Theses formulations are best known for their thick, bluish coating left on plants after an application.
“Growers really dislike this physical characteristic, which we call the ‘blue hue’,” Hornsby said. “Copper hydroxide coating seems to draw moisture out of the plant. It also appears to slow down photosynthesis while temporarily halting growth.”
After spraying higher rates of copper, the Florida consultant describes plants as “tightening and curling up.” Hornsby continues by stating that plant recovery does occur within one to two days. However, she believes the “blue hue” coating does put stress on plants after each application.
For most growers, one to two days of “stress and recovery” following a copper treatment is not enough time to trigger concern for crop loss. However, adding up total stress days following multiple applications over the course of a season results in a much different equation.
Additionally, Hornsby said copper coating does affect the performance of reflective mulch, which is widely used for insect control on tomato and pepper acres in her Central Florida service region. “Coating on reflective mulch puts a strain on our growers,” she said. “After two or more sprays, the reflective mulch gets covered up, which reduces its value and return on investment.”
Developing a copper fungicide that bypasses the negatives of traditionally used inputs has been a major focal point for MANA. After years of research, the company found its answer in MasterCop fungicide/bactericide.
A copper complex formulation of copper sulfate pentahydrate, MasterCop delivers bioactivity for the control of bacterial and fungal diseases on tomatoes, peppers, and other high-value crops.
“As a broad-spectrum fungicide and bactericide, MasterCop gives long-lasting protection and leaves no visible residue,” said Young. “The key to its effectiveness is its patented formulation and small particle size.”
According to Young, particle size matters because copper-based fungicides work by coating the plant leaf surface with minuscule particles of the active ingredient. These particles react with moisture on the leaf surface and release copper ions that kill bacteria and prevent fungal spores from germinating.
According to industry standards, MasterCop is categorized as a low use rate product. MANA recommends MasterCop be applied at 1 pint per acre for annual crops and 2 pints per acre for permanent crops. Higher application rates are allowed for bacterial and fungal disease control when used according to label guidelines for selective crops.
Reducing Soil Loads
Regarding concerns about soil loading from copper-based inputs, the industry is addressing the matter by encouraging grower adoption of practices and products with improved stewardship characteristics.
“Depending on the weather and disease thresholds, it’s not uncommon for growers to spray three or four times a week, explained Cloud. “Adding to the problem is pathogen resistance to commonly used inputs like copper hydroxide. When growers get scared about resistance, they often increase fungicide rates, which can lead to copper loading in the soil.”
From a grower perspective, tomato grower Greg Church from Unicoi, TN, sees inputs like MasterCop as a much-needed solution for this land stewardship scenario.
“The amount of copper going into the soil is a concern for a lot of growers,” Church said. “When copper gets overloaded in soils, we typically have root burn and phytotoxicity. Low-use-rate products like MasterCop, which has less active ingredient in its formulation, will help growers alleviate copper loading in their soils.”
As a reminder to growers, Young said copper-based fungicides should always be integrated with sound cultural practices alongside an understanding of pathogen and disease biology and disease resistance whenever possible.
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