Already weakened by facing the pandemic caused by SARS-COV-2 (Covid-19), the population of southern Brazil, more specifically rural producers in Rio Grande do Sul and Santa Catarina, are frightened by the threat of the arrival of a cloud of South American locusts of the species Schistocerca cancellata.
On June 26, 2020, these insects were in Argentina, about 250 km from the border with Brazil, coming from Paraguay. The cloud has been monitored by Argentines since May 11, 2020; arrived in Argentina on May 21, returned to Paraguay, and on May 28 again reached Argentina.
The grasshopper cycle presents the stages of egg (15-21 days), nymph = leaper (51-89 days) and adult = flying (1st generation, 51-89 days, 2nd generation, 91-155 days). In other words, each individual can live for almost a year.
Experts are studying the factors that lead to the resurgence of the pest in its most aggressive phase. It is possibly due to the combination of climatic factors (high temperature, low humidity, wind, etc.).
They form clouds measuring up to 30 km² (30.000.000 m² or 3.000 ha = 3.000 football fields), made up of approximately 40 million flying insects measuring around 15 cm each.
This population consumes the equivalent of two thousand cattle or 350 thousand people in just one day. They are herbivores and do not affect human health nor are they vectors of disease agents in living beings.
However, this apocalyptic vision of the problem published on social media does not match reality, according to experts: there are already protocols to contain the plague, and there is no reason to worry! Furthermore, the winds, the arrival of cold weather and the lack of food options (we are in the off-season/only pastures available in the region) can bring more peace of mind to the population.
Despite this, the Ministry of Agriculture, Livestock and Supply (MAPA) has already declared a “phytosanitary state of emergency” in Rio Grande do Sul and Santa Catarina (Ordinance nº 201, of 24/06/2020) for a period of one year, with guidelines and measures to be adopted. Although there are already insecticides registered for the South American grasshopper (two commercial products based on deltamethrin/pyrethroid) and another five based on diflubenzurone/benzylurea for Rhammatocerus spp, MAPA already has other alternatives, including biological insecticides, which can be registered on an emergency basis.
Brazilian authorities are monitoring the locust cloud and, if necessary, there are already actions that can be implemented. These pesticides can be applied by land or with agricultural planes. MAPA has already prepared a “Manual of General Procedures for the Control of the Plague Schistocerca cancellata - South American Locust (Serville, 1838)”, with the aim of reducing or avoiding damage and possible losses in the event of an eventual outbreak in Brazil.
Monitoring the pest consists of detecting the presence of eggs in the soil and, subsequently, of nymphs (they do not have the ability to fly). It is necessary to identify the different stages of the nymphs and, if necessary, apply pesticides in bands. Adults can be treated by air or land, first thing in the day.
SINDAG (National Union of Agricultural Aviation Companies) reported that Rio Grande do Sul has a sufficient number of aircraft ready for immediate operation, if necessary. When the adults are in the soil, it is possible to spray them with suitable insecticides in a short time (about 15 minutes). Argentine coaches are taking similar measures; It is important to locate the insects' landing point in time to carry out the operation before dark or early in the morning, before they take flight.
Control is complex due to the locusts' great flight capacity: around 150 km in one day. The time interval in which it is possible to apply insecticides is short and occurs when there is little visibility.
There are around 12 thousand species of grasshoppers and only ten are agricultural pests. Several outbreaks have been reported around the world. They feed on native and cultivated plants. They form dense migratory “clouds” under favorable climatic conditions, 10 km long by 3 km wide, equivalent to 3.000 ha (3.000 football fields). When they land in the late afternoon, they huddle together, occupying an area of up to 10 ha to feed and remain there until the morning of the following day.
This is not the first time that the phenomenon has threatened a country. On several occasions locusts caused damage. In 1400 BC it decimated crops in Egypt, being considered the eighth biblical plague. There are reports of outbreaks in South America in Argentina (1538), the United States (1874), Egypt and North Africa (2004), Mexico (2006), Israel (2013), Argentina/Bolivia/Paraguay (2015-2017) and East Africa (2019/2020). In January 2020, Pakistan declared a “National Emergency” due to the outbreak. China proposed sending 100.000 ducks to combat 400 billion locusts; in this case it was another species: the desert locust, Schistocerca gregaria.
In Brazil, outbreaks have already occurred in 1880 (PB, RN), 1917 (RS), 1933-1947 (RS, SE), 1980 (MT) and 1984 (MT). In MT the species present was Rhammatocerus schistocercoides. In isolation, they do not cause significant damage to crops, being considered secondary pests.
This threat may become more frequent. Therefore, it is advisable to develop a permanent strategy against the problem.
On July 2, 2020, a video conference is planned involving experts and representatives from the Ministries of Agriculture of Brazil, Argentina and Uruguay, with the aim of aligning actions to combat the pest. FAO/UN will also be involved, as the institution maintains an international program to combat locusts.
By José Otávio Menten, President of the Sustainable Agro Scientific Council (CCAS), Agronomist and Senior Professor at ESALQ/USP
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