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Fungicide not ‘silver bullet,’ could help against coffee leaf rust

Farmers concerned they won’t have time to spray before harvest

Healthy coffee beans and flowers are displayed at the Maui AgFest in 2016. With Hawaii’s $56 million coffee industry at risk from coffee leaf rust, the state Department of Agriculture is considering the use of the fungicide Priaxor Xemium to battle the pathogen that’s invaded Maui, Lanai, Hawaii island and Oahu. The Maui News / MATTHEW THAYER photos

Coffee farmers may have a new tool to use in the near future to combat coffee leaf rust, a threatening pathogen that has been found on Maui, Lanai, Hawaii island and Oahu.

With Hawaii’s $56 million coffee industry at risk, the state Department of Agriculture has filed a draft request for emergency exemption with the U.S. Environmental Protection Agency to allow the use of a fungicide, Priaxor Xemium, on coffee plants, a request it expects to be approved by the end of April.

“I just wanted to remind growers that the product, if we get it approved for use, is not meant to be the magic silver bullet that everybody may be expecting,” Andrea Kawabata, assistant extension agent for the Department of Tropical Plant and Soil Sciences Office, said Thursday during an informational webinar for farmers. “But it is meant to be a protectant on the leaves and to be able to be transmitted trans-linearly through the leaf and to protect new developing leaves from additional coffee leaf rust infection.”

Coffee leaf rust was first discovered in Sri Lanka in 1869 and can cause devastating impacts to vegetative and berry growth. There is no easy and natural way to remove rust, and according to the DOA, the disease has multiple long-term impacts, including tree dieback, which result in a 30 to 80 percent loss to the next year’s crop.

The pathogen has taken hold in all major coffee-growing areas of the world but had not been found in Hawaii until its discovery on Maui and Hawaii island in October, then on Oahu and Lanai in January. The Board of Agriculture has since restricted the movement of coffee plants from these islands.

Hawaii State Department of Agriculture Biological Control Section Entomologist Mach Fukada shows a photo of coffee rust on a leaf while inspecting coffee plants growing along Iao Valley Road in January.

Greg Takeshima of DOA’s Pesticides Branch said Thursday that Priaxor Xemium has proven to be effective against coffee leaf rust in several case studies outside of the U.S., like Brazil and Costa Rica, which is why Hawaii is pursuing the product.

Priaxor is currently approved for use on other agricultural crops, but EPA approval is required to add coffee plants to the list of exemptions on the label, said Mitchell MacCluer of DOA’s Maui Education Section.

This process of approval and updating labels can take up to two years.

Priaxor is only sold by the gallon and averages about $45 per acre per application, not including labor. It has the ability to protect against coffee leaf rust spores from germinating and growing on the coffee plant leaves, unlike currently approved contact fungicides that kill spores on the outside of the leaf.

The fungus must come into physical contact with coffee plants in order to survive.

In addition to the DOA’s request for a state of emergency for coffee leaf rust, Takeshima said the department requested that current certified organic farmers do not lose their status as organic if using Priaxor because “we understood that that was an important part for farmers.”

However, growers cannot sell their coffee products as organic once the fungicide is applied to trees they plan on harvesting from that season or advertise as pesticide-free.

Protective equipment — such as chemical-resistant gloves, approved filtering respirator and protective eyewear — is required while handling the product, according to MacCluer.

It can only be applied twice per year to field-grown coffee crops, which provides about 14 to 21 days of protection against any infection or germination.

“Good coverage is going to be critical by getting that product into the leaf, so it can provide the protection from any spores,” Kawabata said. “The contact fungicides that we currently have available to use on coffee now won’t do that, so in between your spray applications with Priaxor, it’s giving that added protection.”

MacCluer said that it’s a violation of federal law to apply Priaxor in a manner inconsistent with the label.

The fungicide application rate is limited to 7.14 fluid ounces per acre. It also must be diluted with a minimum of 20 gallons of water per acre via a ground applicator, meaning no aerial sprayers or drones.

During the application of Priaxor, the user must be in possession of both the container label and the Section 18 label with the newly listed coffee plant, MacCluer said.

Some farmers, however, are worried that they may not have time to apply the fungicide this season before the harvest that starts around August. Once farmers spray Priaxor, manufacturers say they must wait 45 days until harvesting from the plants.

“The 45-day pre-harvest interval is a sticky point, but unfortunately that was what was provided to us by the manufacturer, so they don’t play with dates and times,” said Takeshima. “The amount of time it took to get everything together might not coincide with this harvest.”

Growers would still need to rotate in other products between Priaxor applications throughout the year in order to control coffee leaf rust, Kawabata said.

Other restrictions include having a 25-foot barrier from the point of application and the edge of the field, maintaining a vegetative buffer strip between the sprayed area and the downward slope to prevent potential runoff and not applying Priaxor when wind speeds exceed 15 mph or during temperature inversion.

Priaxor users need to notify the state DOA at least seven days prior to spraying the product via email at hdoa.sec18@hawaii.gov. Once Priaxor is applied, the user has 10 days to report to the DOA with information about when and how the fungicide was used, including the farmer’s full name, the farm name, farm address, data and time of the application, age of the crop, target pest (coffee leaf rust), dilution rate, amount of water used and other details.

Farmers said during the webinar that the amount of personal information, restrictions and regulations needed in comparison to other products “didn’t seem reasonable.”

However, based on what researchers know about Priaxor Xemium, Takeshima said that “in order to receive the exemption (from the EPA), we need to fulfill what’s requested of us.”

Information will be used for enforcement purposes, in which a random report will be selected for inspection, he added.

Some small farmers requested that Priaxor be sold in smaller quantities — it’s currently only sold per gallon by manufacturers — or that an appropriate sharing system be created.

Neighbors can share as long as money is not exchanged, but the problem comes down to the container and having the proper product labels.

“You cannot put this product into what are called service containers. Those containers are for temporary use only,” Takeshima said. “Some of the dealers were trying to figure out ways to help you folks, help the smaller farmers, because the product is not necessarily cheap.”

Takeshima reminded growers that “this is a draft” and that more information will be provided once finalized. The department will also create a list of frequently asked questions and have another free webinar in the next few weeks.

For more information or to view previous webinars, visit hdoa.hawaii.gov.

* Dakota Grossman can be reached at dgrossman@mauinews.com.

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