Jul 23, 2020

Three Swarms of Locust now in N. Argentina and S. Paraguay

Author: Michael Cordonnier/Soybean & Corn Advisor, Inc.

For the last three months there has been an ongoing concern about swarms of grasshopper/locust in Paraguay and northern Argentina. The National Agricultural Sanitary and Quality Service of Argentina (Senasa) has now indicated that there are now three swarms of locust in the region. Two swarms are moving across northern Argentina and a third swarm has formed in the Chaco region of Paraguay. In fact, all three swarms started in the Chaco region of northern Paraguay.

The first swarm moved out of southern Paraguay into northern Argentina at the end of May and has since been moving south. The swarm is now located in the province of Entre Rios near the border with Uruguay. Over the last few weeks, the swarm had been relatively stationary due to cold temperatures, but it has started to move again with hotter and dryer conditions.

Now that the weather has turned hotter and dryer, the first swarm is moving about 30 kilometers per day across northeastern Argentina. Senasa has completed several insecticide application on the first swarm and it is now about 30% smaller and occupies an area of approximately 10 square kilometers (approximately 2,500 acres).

A second swarm has just moved out of southern Paraguay into northern Argentina in the province of Formosa and is heading toward the province of Chaco.

The National Vegetative Health Service of Paraguay (Senave) has now identified a third swarm moving out of the central region of the Chaco Department in Paraguay heading toward the border of northern Argentina. Senasa has indicated that the third swarm might enter Argentina in the province of Formosa or Salta.

Brazilian officials are keeping a close watch on the situation, but the locust have not yet entered into Brazilian territory. The main grain crop in the region that could be impacted by the locust is the winter wheat crop, but as of yet, there have not been any damage assessments.

The grasshopper is the species Schistocerca cancellata, which is the major swarming species in subtropical South America and it is also called the South American Migratory Grasshopper. 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.