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July 6, 2020

Appears Locust Swarm in Northeastern Argentina is under Control

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

There has been a lot of news in recent weeks in the Brazilian press concerning a swarm of South American Migratory Grasshoppers or locust that had been moving across northeastern Argentina heading toward southern Brazil. Scientists had said that the swarm could be relatively easily controlled and the local population should not be overly concerned.

Last Thursday, the Argentine government took action and Brazilian authorities are satisfied that the situation now appears to be under control. An aerial application of insecticide was applied last Thursday that covered the majority of the swarm, which measured approximately 30 square kilometers (10 kilometers long and 3 kilometers wide or 3,000 soccer fields) and contained an estimated 40 million individual grasshoppers.

The application was made between 10:00 and 10:45 am while the insects were still on the ground. Technicians from the Argentina National Food Quality and Sanitation Service (Senasa) inspected the area three hours after the application and found part of the grasshoppers dead with others debilitated or flying erratically. Even though the temperatures later in the day warmed up enough for the grasshoppers to start flying, no movement was detected. Technicians returned to the area last Friday to monitor the situation.

Recent cold temperatures allowed for the control measures to be applied successfully. The swarm had not moved since last Monday, which allowed time to identify the swarm's location and make the application. Control measures must be applied early in the day while the insects are still on the ground.

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 localized 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.

There have been 5-6 outbreaks of the South American Migratory Grasshopper since the late 1880's, but they have never caused widespread damage and they are now considered secondary pests. A swarm of that size can consume the amount of vegetation per day equivalent to the weight of 2,000 cows.