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Antestia and its role in altering the taste of coffee.

Potato defect is a complicated disease, with no easy solution to fight it. Lack of incentives and best practices create an environment primed for potato defect in certain coffee-growing regions. In the hope of finding ways to prevent the disease, there is ample research focused on antestia, the insect linked to the defect.

Floral, earthy, chocolatey and spicy are all words that have been used to describe the taste of various roast profiles. Roasters and consumers alike have become awakened to the possibilities of coffee worldwide including Arabica from Rwanda and Burundi. On the flip side, there is increased awareness of the challenge of purchasing consistent taste profiles from these two regions. Regions where one defective bean can dramatically alter the taste of an entire batch of coffee. Commonly known as the "potato taste defect," due to both the strong taste and aroma of raw potato that is emitted when the beans are infected, approximately 2-3 percent of the beans from these two regions have been infested.

To date, the potato defect has been identified in the Africa Great Lake Regions, mainly Rwanda and Burundi. This is not the first outbreak--in 1916, there was an outbreak in Uganda, and there are additional reports of infestation in the 1940s by Belgian researchers. These reports found that areas that were infected with antestia (Antestiopsis spp.), the insect linked to the defect, had both the leaves eaten and the hole pricked in the cherry, causing the cherry to die and fall off. These antestia outbreaks in the mid 1900s and beyond, resulted in lowering the yields by up to 40 percent. However, farmers were not growing the beans to meet quality standards, and so, the impact of the disease was not as profound.

Today, the demand for single origin, high quality coffee is extremely valued with coffees being cupped, evaluated and prized for their taste profiles. One single infected bean can destroy an entire cup. Originally, the blame for the potato taste was exclusively placed on the antestia beetle. However, there are other coffee-growing regions that have the antestia beetle, but do not have the defect.

So, what is it about Rwanda and Burundi that makes it prone to the defect? On further investigation, the antestia beetle appears to be a variable that creates an environment that is primed for the potato defect to occur. There also appears to be an increased prevalence of the infestation on farms with low coffee productivity. Joseph Bigirimana, PhD student in the department of entomology at Michigan State University, East Lansing, Michigan, said that East Africa is losing USD 45 cents of its coffee yield as a direct result of the potato defect.

Entomology of Antestia

In just one year, there can be up to four generations of antestia at a coffee plot, with the average life span of a beetle lasting between three to four months. Part of the Hemiptran family, the variegated bugs have piercing mouth parts that allow them to suck plant juices. Their favourite juice of choice happens to be the Arabica plant, with a preference for unripe coffee cherries.

Research, shared Bigirimana, is looking at the relationship between the insect and the occurrence of the potato defect, including examining the damage that the insect has inflicted on the plant. Although there is a definite link between the two, there are still several uncertainties, including when the berry becomes infested and what makes this region more prone to the defect. "We are actually trying to find out what are the distributions of the defect across the country, and what are the other management practices related to the defect," said Bigirimana.

Researchers are stumped as to both how and when the bacteria that creates the defect is getting into the cherry. Are the bacteria in the environment? Soil? Or on the mandible of the insect. "What we do know is that whatever the pathway, eventually it gets into the cherry, creating the raw potato flavour," said Daniel Clay, director global programs in sustainable agri-food systems, Michigan State University, East Lansing, Michigan.

Controlling Antestia

Although there is some uncertainty about whether the bacteria is carried into the plant from the antestia beetle, there is a high correlation between the prevalence of the insect and the defect. Several strategies are recommended including good pruning so that the beetles lose their hiding spaces, and creating healthier trees using fertilizers and mulch. The hope is that these practices will reduce both the areas for the insect to hide, while also creating healthier, resistant coffee trees. As an additional benefit, each of these best practices will help increase the overall production level of the farm. The farmer will obtain stronger, resilient trees and healthier cherries to sell at the market.

Pest control is also a part of this study, with the hope that if the antestia beetle is controlled, so will the disease. "We know that when we control antestia it limits the amount of punctured cherries, which appears to be how the bacteria is getting into the bean," said Clay. Experimental fields, reported Clay, are testing the efficiency of pyrethrums as part of an integrated pest management strategy. Pyrethrums are organic products, created from the plant oil in the pyrethrum daisy. The initial applications have been effective in helping control the antestia beetle. Researchers from Michigan State University, have called this process "The Antestia Knockdown and Count."

The application of the organic pesticide begins with placing a white sheet around the coffee trees prior to spraying. The pyrethrum is then sprayed to the trees, after 10 minutes, the researchers will shake the trees and count the amount of antestia beetles that have been "knocked down" by the spray. "We are looking at the whole combination of best practices and different methods of controlling antestia to see what is most effective," said Clay.

Although there is not a direct link between antestia and the defect, controlling the insect population appears to reduce the infestation. However, there are several factors that constrain farmers from adopting the best practices including the pyrethrum application. "These practices require an investment from the farmer," said Clay. "Investing in best practice has two sides, it has to do with both the capacity of the farmer to invest and the investment incentive." Farmers can have both the knowledge and the capacity to apply best practice, but if the incentive isn't there, if investing in these practices does not result in an increased profit, then there is no reason to do it.

Best practices, including higher productivity and a denser cherry, appear to play a role with relieving the infestation. When farmers adopt best practices, including fertilizing the trees and adding nutrients to the soil, said Clay, and make an investment in their farm, it appears to lower the potato taste. However, adopting best practices is far from a simple process.

Lack of Incentives

Cherry prices in Rwanda are extremely low, explained Clay, and so for the farmer there is a low incentive to shift towards best practices. "Cherry prices are negotiated with the coffee board every year but farmers never seem to get a fair shake of it," said Clay. To fully address the potato defect, researchers need to look at both the biology of the disease and the economics. Michigan State University is currently engaged in researching the policy engagement side with the intent to help the industry understand the necessity of increasing the price of cherry. "If the industry doesn't create the incentive, [the reality is that] farmers will not make the investments that they need to so that they control the potato taste," said Clay.

Producing coffee is extremely price sensitive, and farmers might be able to use their own family labour for harvesting. But if they are looking to invest in pruning and fertilizing, the farmer will need to hire most of the labour. "The farmers will tell you that with current labour rates that they will lose money in coffee, that it costs [them] more to produce than [they] can get for it," said Clay. "So, then they opt to not invest in the production."

Making the shift involves working with the value chain in the coffee sector to understand the need for higher cherry prices and finding ways to renegotiate so that the farmers have both the incentives and willingness to invest in their coffee. On a positive note, the cherry price is higher this year, paving the way for farmers to invest in their farms.

Potato defect is a convoluted disease without a simple, one path solution. Current research is looking at several factors to discover why Rwanda and Burundi appear to be primed for the defect. This includes investigating the economic and biological factors that have put the area at increased risk. There are several questions yet to be answered, including when the disease is transmitted and what about the Rwanda and Burundi environment make the region more prone to the defect. However, researchers are actively looking for the solutions, including investigating whether there is a direct link between the antestia beetle and the disease.

Anne-Marie Hardie is a freelance writer, professor and speaker based in Barrie, Ontario. She may be reached at:

Caption: The antestia beetle posing on a coffee cherry in the field.

Caption: Experimental fields are testing the efficiency of pyrethrums as part of an integrated pest management strategy.

Caption: Morning count of antestia beetles, which is part of a process called "The Antestia Knockdown and Count."
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Comment:Antestia and its role in altering the taste of coffee.(SPECIAL SERIES PART II: ANTESTIA)
Author:Hardie, Anne-Marie
Publication:Tea & Coffee Trade Journal
Geographic Code:6BURU
Date:Apr 1, 2017
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