Researchers and technicians discuss actions to minimize the advance of the Giant Caruru

Initially detected in the state of Mato Grosso, in 2015, the Amaranthus palmeri, or Giant Caruru, is a quarantine weed, posing a great health risk for Brazil. The second state to detect its presence was Mato Grosso do Sul, in Naviraí farming, at the end of 2022.

To provide knowledge about this exotic weed plant and seek solutions, a seminar was held for discussions between different segments of the agricultural chain, especially agriculture, in a online event. Starting the live, on March 2, researcher Fernando Mendes Lamas, from Embrapa Agropecuária Oeste, moderator of the event, warned: “Amaranthus palmeri is a difficult-to-control, very fast-growing weed that can compete significantly with economic crops, mainly corn, cotton and soybeans”. Researchers and technicians linked to agriculture from 20 Brazilian states and the Federal District participated.

Harley Nonato de Oliveira, general manager of Embrapa Agropecuária Oeste, emphasizes that the weedy plant “causes great concern, not only due to the aggressiveness it affects, but also due to the ability of this plant to select resistance. That is why it is of great importance to have all these institutions [in the online seminar] to debate this subject, contain the spread of this weed in Mato Grosso do Sul and discuss the actions that need to be put into practice. The best way to fight the enemy is to get to know him well and through discussion and sharing of knowledge, find the best ways to contain this plant. And these actions that we will address [at the seminar] serve not only Mato Grosso do Sul but the whole of Brazil,” said Nonato.

Spread of the plant

There are several species of pigweed. At the seminar, the subject was the species Amaranthus palmeri, known as the giant pigweed. This species has a high capacity to compete with soybeans, corn and cotton. What is known is that, possibly, the arrival of Amaranthus palmeri to Naviraí occurred through the transit of agricultural machinery, mainly harvesters, just as it is believed to have happened in the first report of the exotic plant in Brazil, in Mato Grosso, in the year of  2015.

But they can also be spread by natural falls, irrigation canals, fertilizer compounds and animal manure, and by birds and mammals.

Characterization of Amaranthus palmeri

It is a prolific weed, that is, it produces seeds in large quantities, reaching up to 250.000 seeds per plant. The seeds are small, smooth and rounded and their color can vary from reddish brown to black. It can grow between 2,5 cm and 4 cm per day, making post-emergence herbicide applications difficult. The shape of the leaf is creeping and thorny, with leaf blades varying from ovate to rhombic-ovate in shape. It can grow up to three meters in height, has broad leaves and spike-shaped green flowers.

Learn more about the Amaranthus palmeri plant and management methods 

Chemical and cultural control are the best strategies to combat Amaranthus palmeri

Management of glyphosate-resistant pigweed