The Pest Management Network of Aapresid (Argentine Association of No-Tillage Producers) wrote an article pointing to a growing fall in the performance of Bt (Bacillus thuringiensis) technology in lepidopteras control in soybeans. Approved a decade ago in Argentina, this biotechnological event has been widely adopted in the neighboring country, reaching 70% of the soybean planted area in the last two harvests.

Aapresid's research, however, shows a fall in the performance of this technology by users. No less than 89% of respondents currently rate Bt soybeans between bad and satisfactory. In previous surveys most described the technology as an "excellent strategy" for insect management.

It all started when Argentine producers began to observe the presence of Lepidopteras such as the Soybean Caterpillar (Rachiplusia nu) and the Falsa-Medideira (Chrysodeixis includens) during the monitoring of their bt soybean lots. Now, in this harvest, not only was the presence of caterpillars detected, but in many cases damage was observed that, on average, led to the treatment of 56% of the Bt soybean area with leaf insecticides.

Technicians from EEAOC (Bispo Colombres Agroindustrial Experimental Station) collected larvae in the affected lots that were fed in laboratory with bt soybean leaves. About 60% of these larvae completed their life cycle, which demonstrates a change in the susceptibility of the species to this technology.

Changes in the duration of its larval cycle were also observed in relation to susceptible larvae. The same situation has been corroborated in Brazil recently.

Agronomist Enrique Lobos states that, in his region, the area planted with Bt soybean sits about 60% and that the rest of the cultivated area without this event requires 2 to 3 applications for lepidopteran control. Lobos says producers and advisors in the area already admit a technology breach.

The technician considers that, in these circumstances and depending on the pest, Bt soybeans may require the application of insecticides for the control of lepidopterans. Despite this, he maintains that the technology will allow to maintain acceptable levels of control, so that a single application of insecticide may be sufficient.

Agronomist Diego Szwarc of INTA (National Institute of Agricultural Technology) said the problem in the Reconquista area, Santa Fe province, is widespread. The expert considers that there is still a need to generate information on the subject and is therefore initiating a series of investigations to clarify the problem in cases where there is a suspicion of resistance breach.

Bayer announced the suspension of its soybean seeds and biotechnology business in Argentina in the 2021/22 crop. "With lower insect pressure than other regions, Argentina accounted for approximately 10% of the total area sowed with INTACTA RR2 PRO in South America in 2020/2021," the multinational said in a statement.

"The plan is to redirect investments in Argentina to profitable and innovative projects focused on promoting digital transformation and new business models, such as the Orbia digital platform, or Carbon Initiative," Bayer said at the time.

Source: Agrolink