Research generates maps of areas favorable to the development of a quarantine pest that is absent in the country

Specialists from Embrapa mapped areas of Brazilian territory with more favorable conditions for the development of the exotic insect pest Bactrocera dorsalis, absent in the country, but prioritized among those at imminent risk of potential entry. The maps generated will support public policies to prevent the pest, also known as oriental fruit fly, from entering Brazil. As a large part of fruit plants are hosts to the insect, the entry of B. dorsalis is a threat to national fruit farming, due to the damage caused to the fruit and losses resulting from quarantine restrictions imposed by importing countries.

Based on bioecological assessments of the insect and territorial zoning, carried out by Embrapa Meio Ambiente (SP), Embrapa Semiárido (PE), Embrapa Amapá (AP) and Embrapa Territorial (SP), it was possible to identify availability, in almost the entire Brazilian territory, one of the most attacked host plants abroad. The areas with the most favorable conditions for the development of B. dorsalis were observed according to the months of the year. The period between July and October is the one that brings together the largest number of municipalities with these conditions, and, therefore, those with the greatest risks to the entry, establishment and occurrence of plague populations in Brazil. The work is part of the research project “Strategies to subsidize monitoring and control actions for insect pests present and quarantined absent in Brazilian territory – DefesaInsetos”.

Os results These studies were sent to the Agricultural Defense Secretariat of the Ministry of Agriculture, Livestock and Supply (Mapa), to support measures to prevent the pest from entering the country and immediate control actions, in the event of its eventual detection. The oriental fruit fly was one of the 20 missing quarantine pests prioritized by Embrapa and Mapa as those with the greatest potential impacts on Brazilian agriculture. Therefore, it is included in the National Program for the Prevention and Surveillance of Absent Quarantine Pests, which establishes actions both to prevent the entry of exotic pests and to mitigate risks in situations where they are suspected of occurring in the country.

Zoning of areas favorable to the development of the pest

According to the zoning carried out, in the most critical months (July to October), the smallest number of municipalities with favorable areas for the best development of B. dorsalis was verified in July - 923 locations. The month with the highest number of municipalities was September - 1.940. In the months of August and October, optimal conditions for the insect were observed in, respectively, 1.680 and 1.378 municipalities. During this period, the central area of ​​Brazilian territory was the most favorable for the optimal development of the plague.

The month of April presented only five municipalities with areas favorable to B. dorsalis present in the states of Bahia and Minas Gerais. In the months of August and September, municipalities in 15 states appear with these conditions. The South Region appears with favorable areas only in the month of November, in municipalities in Rio Grande do Sul.

In the territorial zoning of Brazilian municipalities, monthly climatic data (temperature and relative humidity) were observed for the period from 2009 to 2018, and the main crops of insect host plants present in Brazil based on the 2017 Agricultural Census. The hosts prioritized in the studies were avocado, banana, cocoa, coffee, cashew, persimmon, orange, lemon, tangerine, beans, guava, apple, papaya, mango, passion fruit, melon, watermelon and tomato.

Insect reproduction and survival

Embrapa analyst Rafael Mingoti, coordinator of zoning studies for the DefesaInsetos project, says that, based on bioecological data on the pest made available abroad, the climatic conditions that allow the insect to have a higher rate of deposition and hatching of eggs were determined, better development of larvae, pupae and adults, greater reproduction and greater survival and, therefore, a faster restart of their life cycle. These are conditions, therefore, that favor the rapid development of the pest, the greatest number of generations and descendants and its establishment in the location.

“These studies are a crucial part of the work. After these assessments, we carry out verification using geoprocessing. We collect data on monthly averages of maximum and minimum temperatures and relative humidity, with a long historical series for the whole of Brazil, and we work with this information so that it is distributed over the entire surface. From then on, we check, monthly, in which places the optimal conditions occur and add a margin of error with standard deviation”, explains the specialist.

Mingoti highlights that the bioecological studies carried out have shown that B. dorsalis has great adaptability and can survive in different conditions. Its survival, therefore, is not restricted to areas where conditions are optimal for its development. However, in these areas faster adaptation and greater numbers of descendants and number of generations are expected. Therefore, these conditions were prioritized in the study to determine Brazilian areas indicated as priorities for territorial monitoring of the insect, given that they will require greater effectiveness in control strategies if the insect enters the country.

Support for monitoring and control actions

Leader of the DefenseInsetos research project, Embrapa researcher Jeanne Scardini Marinho Prado draws attention to the need for agility in offering monitoring and control alternatives that are capable of effectively reducing the population of a new pest. According to her, in most cases, the lack of prior information about these exotic organisms means that the presence of the insect pest has its detection postponed or effective control strategies become unfeasible. “For this reason, all the work developed is an important territorial management instrument to support the strategic actions of the Program established by Mapa and, consequently, prevent further damage to national crops”, she highlights.

According to Embrapa researcher Maria Conceição Peres Young Pessoa, the entry of a quarantine pest that is absent in the country can be more worrying when this insect pest finds climatic conditions conducive to its optimal development and rapid dispersion. This situation, according to her, can be aggravated when these insects are polyphagous, as is the case of B. dorsalis, favored when the greater diversity and distribution of areas planted with their main hosts are found and available at different times of the year. “This explains why state areas favorable to the best occurrence of the insect were observed in all months of the year”, adds the researcher.

In the assessment of the head of the Plant Protection Coordination of the Agricultural Defense Secretariat of Mapa, Graciane Gonçalves Magalhães de Castro, the risk of introduction and establishment of the pest in Brazil is very high, as a result of the increase in the flow of people and goods from of the countries where the plague has been occurring in recent years. Therefore, according to her, zoning with the delimitation of more susceptible areas and definition of risk routes provides important intelligence information to optimize prevention and surveillance actions carried out by Mapa technicians, in partnership with the state Plant Health bodies in All country.

“The results of these studies will allow the surveillance workforce to be directed to stop a possible introduction or take control and eradication measures of a possible outbreak of Bactrocera dorsalis. This will be fundamental in structuring the specific prevention and surveillance plan for this pest”, says Castro.

For Rafael Mingoti, the information and zoning available can also help producers make decisions, who, knowing the location of their property, will be able to check in which months of the year there is a greater risk of an attack by the oriental fruit fly in your fruit trees. “With this information, they can prepare and train their people. Instruct them to stay alert and know how to identify and combat the pest. And as it is an exotic insect, one of the actions to take, when identified, is to notify Mapa”, he says.