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New glyphosate-resistant weed is detected in Argentina

Argentina confirmed that Digitaria insularis is resistant to glyphosate and has invaded crops in the Northwest and Northeast regions of the country, and in the south of the Santa Fe province. This weed was previously classified on an yellow alert for suspected resistance to glyphosate.

The dose-response test to verify resistance was done by the Center of Herbicides Assessment of the Agrobiotechnology Institute of Rosario. The resistance index was 11.8, which means that a dose of 12 times higher would be required to control the Digitaria insularis comparing to non-resistant ones.

Both Paraguay and Brazil already had identified the Digitaria insularis biotypes resistant to glyphosate in 2005 and 2008, respectively. Currently, this specie is one of the major problems in both countries, and spreads rapidly in Brazil.

Digitaria insularis is a perennial weed, which competes with summer crops such as soybeans and corn. Moreover, it germinates very superficially, and is perfectly suited to no-tillage.

"The germination is insensitive to light and has a high germination. In environments of Brazil, it starts to form rhizomes 45 days after germination, so it must be controlled before that period, and it takes 60-70 workdays to flower.

Luis Henrique, expert of ABC Foundation in Brazil, revealed that pre-emergence control gives good results. The herbicides used include metolachlor, imazethapyr and clomazone. For post-emergence control, results can be improved with mixing of glyphosate, Henrique said. Meanwhile, in corn they found very effective the use of mesotrione, nicosulfuron or glufosinate ammonium for tolerant hybrids.