The plague

I thought that my earlier post on Ethiopia was the last but I was wrong.

Something that happened two days ago at our farm in Salta reminded me of an incident at Bedele worth mentioning and that somehow seeped through the cracks of my memory (oh surprise!).

While de-weeding one of the fields I saw a swarm of immature locusts. These were nymphs of the soldier locusts (Chromacris speciosa), unmistakable with the shiny black and red markings. They are widely distributed in Brazil and Northern and Central Argentina.

Nymphs of Chromacris speciosa, rather striking insects.
Adult of Chromacris speciosa.

The first memory that came to mind was of my father, an Agronomist in charge of pest control in Uruguay, who told me about locusts for the first time. He described the enormous clouds that would obscure the sun and that his Jeep (Willys) would skid on the mass of insects and needed to engage 4WD to be able to move!

Then I remembered the day in Bedele when, although it dawned with a clear sky, suddenly, as it happens during the sun eclipses, light faded for no apparent reason. This lasted for a few minutes until the locust swarm arrived and landed on us! They covered the ground and landed on trees stressing branches to the point of breaking. Most of the green matter available was consumed within hours and they moved on as a wave, leaving scorched earth behind.

A desert locust swarm. Credit: FAO (http://www.fao.org/locusts/resources/photos/en/).

The invasion only lasted for a couple of days until they moved off. During this time we were the target of a very unpleasant experience when, without warning they would land on your back and prick you with their spiny legs!

We were suffering the impact of a periodic swarm of the desert locust (Schistocerca gregaria), found mainly in Africa. Interestingly, this insect can change its body in response to changes in the environment. Although this takes several generations, a solitary, shorter-winged (non-migratory form) can turn into a social locust that, because of being long-winged can travel really long distances in search of food.

When this happens, they can cause severe and extensive damage to food crops and fodder as a classic swarm can be as numerous as 150 million individuals, capable of covering hundreds of km in one day when on the go. Because of their transboundary nature, its spread must be monitored in various countries to control them while they are still not able to fly, usually in dry areas. This activity requires collaboration between countries through specialized bodies such as FAO and the Desert Locust Control Organization for Eastern Africa (DLCO-EA).

Finally, the rather nice grasshoppers we get in our gardens in Zimbabwe, known as Green Milkweed Locust or African Bush Grasshopper (Phymateus viridipes), are also capable of long migrations but they are not a pest although, to our annoyance, they are capable of eating our flowering plants.

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