Swarming Locusts (Grasshoppers) Worries Argentina and Brazil

Author: Michael Cordonnier

As if Argentina did not have enough problems to worry about with the Covid-19 pandemic and a collapsed economy, they are now dealing with swarms of grasshoppers in the northeastern provinces of the country.

Farmers in southern Brazil are concerned about potential damage from the grasshoppers, but it looks like the swarm from Argentina might move into northern Uruguay first before potentially entering into southern Rio Grande do Sul.

The map below shows the progression of the swarm from southern Paraguay on May 30th to the province of Santa Fe on June 20th to now onto the border where Brazil, Uruguay, and Argentina meet. The current weather might help to control the pests. Grasshoppers need temperatures of at least 25 degrees C (mid-70's F) in order to be active and they like dry conditions. The weekend weather in southern Brazil was cold and wet, which might slow them down and result in increased mortality.

As a precaution, Brazil has taken preemptive action by declaring a phytosanitary emergency in the states of Rio Grande do Sul and Santa Catarina. The Brazilian Minister of Agriculture said that the declaration of an emergency was made in order to allow the mobilization of human and financial resources to get ahead of any potential problems the grasshoppers could cause. The state of a phytosanitary emergency will stay in effect for one year.

The state of Rio Grande do Sul has already positioned 46 agricultural airplanes on the border with Uruguay in the event the swarms head toward Brazil. The Brazilian National Syndicate of Agricultural Aviation Companies (Sindag) advised the federal and state governments that they are putting 426 agricultural airplanes at the government's disposal should they be needed to combat the potential infestation.

The Secretary of Agriculture for the state of Santa Catarina called a meeting last week to develop a plan of action should the swarms of grasshoppers in Argentina start heading toward Santa Catarina, but that is a remote possibility.

One good thing is that southern Brazil is heading into their "winter season" so that the main crop that could be impacted is winter wheat. Farmers in southern Brazil will start planting their spring crops in August and September. Until then, the main impact in Argentina and Uruguay might also be the winter wheat crop. Farmers in southern Brazil are being advised that they do not need to do anything at this time and they should not indiscriminately apply insecticides which would be a waste of money.

The grasshopper is the species Schistocerca cancellata, which is the major swarming species in subtropical South America. This species shows typical locust phase polymorphism. Locusts are a collection of certain species of short-horned grasshoppers that have a swarming phase. These insects are usually solitary, but under certain circumstances they become more abundant and change their behavior and habits, becoming gregarious. No taxonomic distinction is made between locust and grasshopper species: the basis for the definition is whether a species forms swarms under intermittently suitable conditions.

This species is also called the South American Migratory Grasshopper and it has been causing problems in Argentina for over 60 years. At the start of the twenty century this grasshopper was considered a major pest threat in Argentina causing extensive damage to crops and pastures. Intensive control measures in the early 1950's helped to control the damage. In recent years there has been sporadic outbreaks of the swarming insect.

The map below was published in Noticias Agricolas and it shows the movement of the swarm over the past month.