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July 20, 2020

New Swarm of Grasshoppers/Locust forming in Paraguay

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

A second swarm of grasshoppers/locust has formed in the Chaco region of Paraguay according to the National Seed and Vegetative Quality Service of Paraguay. It is unsure which direction the locust will move, either toward the border of Bolivia and Argentina or toward the border of Bolivia and Brazil.

At the end of June a swarm of locust was located in northeastern Argentina near the border with Brazil, but the swarm was essentially stopped by cold temperatures and rain. The Argentina government conducted several insecticide applications which helped to control the swarm, but it was cold temperatures and rain that essentially kept the swarm on the ground. The locust like warm and dry conditions and there is a concern that the swarm will start moving again once the temperatures warm up.

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 Paraguay and Argentina for over 60 years. In recent years there has been sporadic outbreaks of the swarming insect.