New species of caterpillar attacks soybeans with biotechnology in Brazil

A 'new' species of caterpillar has been attacking soybeans with Bt (Bacillus thuringiensis) biotechnology – which should confer resistance to the pest.

Rachiplusia nu

According to an alert from specialists, it is Rachiplusia nu, which appeared under high pressure in several points of the Brazilian agricultural frontier and was characterized by the plant's high defoliation power.

″From what we noticed, the caterpillar pressure increases in the crop after the season, and the trend is that this will become a new problem. Rachiplusia nu is an important defoliator. It leads to a decrease in the crop's leaf area and potential losses of around 30%,″ pointed out Germison Tomquelski, a researcher at Desafios Agro, in Chapadão do Sul (MS).

Germison Tomquelski, a researcher at Desafios Agro

According to Tomquelski, the country's central region, including Mato Grosso do Sul, was one of the areas most affected by the caterpillar.

″There are still cases located in Goiás, Minas Gerais, São Paulo, Mato Grosso, and Paraná,″ observed the researcher, who, after traveling through several productive areas of the country in recent months, revealed that the 2022-23 harvest marked the greatest pressure from Rachiplusia observed until today.

The same alert was made by researcher Henrique Berto from the technical staff of the consultancy Agrotec, which has operations extended to areas of Mato Grosso do Sul (Chapadão do Sul, Paraíso das Águas and Campo Grande) and the southwest of Goiás.

Henrique Berto, Agrotec

The specialist closely monitored the increase in pressure from the Rachiplusia nu caterpillar and pointed out that the rise in average temperature in the producing regions contributed to increasing the pressure of the pest in this soybean crop.

″Pest management is critical. Within our service areas, the pressure was uniform. The difficulty of identifying whether it is Chrysodeixis includens or Rachiplusia nu often leads producers to believe that Intact soybeans will control the pest,″ he said.

Assist Consult made a similar observation, drawing attention to attacks by Rachiplusia nu on commercial Ipro soybean crops in Mato Grosso.

According to the company, samples of the caterpillar are now being evaluated in the laboratory, and its specialists consider it essential to define already effective measures to control the pest.

Germison Tomquelski, from Desafios Agro, emphasized that the initial recommendation to the producer is to monitor crops and use suitable insecticides, in the face of significant pest populations.

He reported having noticed that baculoviruses act effectively on Rachiplusia nu, alone or integrated with chemical insecticides, depending on the degree of infestation: ″Every care is welcome. The pest has a fast cycle and causes great defoliation.″

Marcelo Lima, an agronomist and technical manager at AgBiTech Brasil, a developer of baculovirus-based bioinsecticides operating in the country, revealed that Rachiplusia nu was rare in agriculture, especially in the Cerrado region. As of 2021, he noted, ″the pest has become more important due to the presence of Bt (Bacillus thuringiensis) in soy.″

Marcelo Lima, an agronomist and technical manager at AgBiTech Brasil

″It is another species of the false sore-mead, easily confused with Chrysodeixis includens. You can only see the difference between them with a magnifying glass.″

Concern about the pest reinforces Lima, until recently, was restricted to around 10% to 15%, in areas planted without soybeans with Bt biotechnology. ″Today it is known that attacks can affect 100% of the crop,″ he warned.

According to Lima, the good news is that AgBiTech should launch a specific technology for controlling Rachiplusia nu, later this year. The agronomist also added that the results associated with this solution, evaluated with the participation of several specialists in commercial and research areas, have been highly satisfactory.

″The bioinsecticide has consistent efficacy data on the pest. It tended, therefore, to become a strategic tool for soybean growers to correctly and successfully handle Rachiplusia nu,″ Marcelo Lima said in conclusion.

(Editing by Leonardo Gottems, reporter for AgroPages)