South America Calling

SAO PAULO (DTN) -- A new type of earworm, Helicoverpa armigera, has triggered the kind of panic among Brazilian soybean farmers not seen since the appearance of Asian rust fungus back in 2003.

Ever since the caterpillar, also known as the cotton bollworm or corn earworm, appeared from nowhere to cause as much as $900 million in damage to cotton and soy crops in the northeastern state of Bahia last year, farmers across Brazil's vast soy belt have been worrying about the pest's inevitable spread and its impact on their world-leading crop.

And spread it has.

With the soybean season just six weeks old, large earworm populations have already been reported in Mato Grosso and other states in the top-producing Cerrado region.

"Farmers are already having to work hard to control the caterpillars in some areas," said LuizNery Ribas, technical manager at the Mato Grosso Soybean and Corn Growers Association (APROSOJA-MT).

There are reports of Mato Grosso farmers who have already applied insecticide three times to control the pest. These are extreme cases, but constant monitoring to spot an uptick in populations will be vital in limiting the damage caused by the caterpillar.

"Farmers are going to have to live in the fields to control this pest. If we are on top of the situation, we can manage it. If not, then we could see big losses," said APROSOJA's Ribas.

Brazilian farmers are used to dealing with Helicoverpa caterpillars, but the alarm bells were raised in early 2013 when an apparently more-resistant variety took hold in Bahia, wreaking havoc as it munched through soybean pods and cotton bolls, after an extended dry spell prevented farmers from spraying effectively.

Eventually, they identified the new variety as Helicoverpa armigera, a caterpillar common in Asia, Oceania, Africa and Europe but previously not identified in the Americas. The earworm version familiar to U.S. farmers is Helicoverpa zea.

Once they knew what they were looking for, agronomists started spotting the armigera caterpillar across the Cerrado region and, to a lesser extent in the south. It has been particularly found in second-planting crops, such as corn and sorghum, during the winter.

"From the elevated winter populations, it was obvious that we were going to have a problem in 2013-14," said Enoir Pellizzaro, chief agronomist at the C. Vale cooperative, which operates in the center-west and south of Brazil.

The Helicoverpa armigera caterpillar is a formidable foe. In India and China, up to half of all insecticide applications are focused on controlling it.

Farmers in Bahia witnessed firsthand that, once the caterpillar got a foothold, the available insecticides couldn't control it in dry conditions.

In Australia and Asia, emamectin benzoate is the principal chemical used to combat the earworm, but its use is prohibited in Brazil.

In April, the Agriculture Ministry announced it would lift restrictions on the chemical, but environmental concerns about its levels of toxicity have delayed the official authorization.

It's a concern as Brazil needs these new molecules to effectively control the threat, said Jose Tadashi Yurimori, one of Brazil's leading soy researchers with 40 years of experience.

USE YOUR WEAPONS WISELY

In the meantime, farmers have to use the weapons at their disposal wisely.

Indiscriminate spraying born of the panic is a major concern among researchers.

"If farmers go out spraying twice a week, we could create resistant strains and then we are in real problems," explains Ribas.

Early spraying is important, though, especially where there are a lot of fully-grown caterpillars left over from the winter crops in the Cerrado.

Worryingly, there is a shortage of the most highly recommended chemicals, including methomyl-based insecticides.

C. Vale is recommending that farmers use alternative insecticides early in order to hold back the big guns for later in the season.

Inevitably, the earworm's appearance will force farmers to spend more on chemicals this year.

How much more will depend on how well farmers manage the situation.

"We are working hard to explain to farmers that the timing of applications is more important than the quantity of chemicals applied," said APROSOJA's Ribas.

C. Vale is working on the idea that farmers will, on average, spray an extra two or three times in the Cerrado this year, says Pellizzaro.

Currently, farmers in this region spray insecticides three to five times a year.

According to Alex Utida, president of the farm association in Campo Novo do Parecis, northwestern Mato Grosso, his chemicals bill for the 2013-14 soy season will rise 30% to $69 per acre.

Agronomists are also concerned that farmers will concentrate efforts on Helicoverpa armigera and neglect other threats. After all, Asian rust remains much more dangerous to the soybean crop.

WHERE DID THAT COME FROM?

Researchers don't know how the Helicoverpa armigera was first introduced but believe that the widespread use of Bt-corn as a second crop could have promoted its reproduction. That's because the Bt bacteria used reduces the population of Spodoptera (armyworm) moths, which are the natural enemy of Helicoverpa caterpillars.

Backing up this theory, populations of all caterpillars have climbed across the grain belt over the past two years.

The practice of planting a second crop of soybeans directly after harvesting the first may also have helped support populations, according to Tadashi.

The government restricts soybean planting for 90 days in the winter, but some farmers ignore the directive.

If this planting scheme is a cause, it's a worry. With prices for second-crop corn looking terrible this season, many more farmers are likely to plant back-to-back soybean crops in 2013-14.

LEARNING TO LIVE WITH AMIGERA

By developing tropical grain farming, Brazil farmers revolutionized agriculture.

But a lingering issue has been the lack of winter frosts to break pest and disease cycles. The climate makes new pests a constant concern.

Still, agronomists are confident that farmers can learn to live with this new caterpillar.

"We learned how to control Asian rust, and we can control this new threat too," said APROSOJA's Ribas.

"It is just a question of finding the right strategy and the right chemicals," he added.

Brazil is forecast to produce between 86 million and 89 million metric tons (mmt) of soybeans this season, up from 82 mmt last season.

Alastair Stewart can be reached at alastair.stewart@telventdtn.com

(AG/GH/BAS)

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