Study identifies new natural enemy of the green stink bug

Researchers have recorded the fly for the first time Trichopoda ypiranga parasitizing adults of green-bellied stink bug, Diceraeus melacanthus. The study took place in agricultural areas of the mid-north of Mato Grosso, between October 2021 and February 2025. The result reinforces the potential of this natural enemy in integrated pest management programs.  

The research evaluated 43 samples of soybeans, cowpeas, millet, sesame, and weeds. The collections covered nine municipalities in the region. In total, the scientists collected 7,754 adult Diceraeus melacanthus. Of this total, 703 showed parasitism. The average rate reached 9.06%.

Rates varied from 1,04% to 30,83% across sampling periods. The highest rates were observed between March and May. The highest averages occurred in millet areas, with 30,8%, and sesame areas, with 17%. In May, approximately 25% of the stink bugs collected in millet and sesame showed signs of parasitism.

The species Trichopoda ypiranga accounted for approximately 84% of the emergencies recorded in Diceraeus melacanthus. The researchers also observed Cylindromyia brasiliana, Gymnoclytia sp. and Phasia sp., but less frequently. The paper also reports the first observation of Phasia sp. parasitizing Diceraeus melacanthus.

Bedbug in the field

In the mid-north of Mato Grosso, soybeans predominate during the summer, between September and February. Corn follows, from February to June. This sequence favors Diceraeus melacanthus because both crops act as hosts. After the soybean harvest, the insects can take shelter in crop residues or weeds. Then, they migrate to attack corn seedlings.

The data showed variation in parasitism throughout the soybean cycle. Values ​​ranged from 2% to 23%. Sampling included weeds before sowing, areas during harvest, and areas after harvest. The highest rate occurred at the beginning of soybean development.

According to researchers, millet and sesame can offer favorable conditions for parasitoid activity. These crops can provide food, shelter, a suitable microclimate, or less interference from agrochemicals. The study also reports that these areas receive less spraying compared to soybeans and corn. Therefore, they can act as reservoirs of parasitoids in the region.

Parasitism rate

Despite the constant presence of Trichopoda ypiranga, the overall parasitism rate was considered moderate. The study points to the intensive use of insecticides as a possible factor associated with this result. Non-selective chemicals can reduce the population density of natural enemies, affect the search for hosts, and compromise the emergence of parasitoids.

Scientists cite acephate as a product widely used in annual crops in the mid-north of Mato Grosso. In greenhouse tests mentioned by the researchers, corn plants sprayed with half the dose and the recommended dose caused 100% mortality of parasitoids within 24 hours.

Chemical control of bed bugs in Brazil utilizes broad-spectrum insecticides, such as pyrethroids, neonicotinoids, and organophosphates. The study highlights the need to integrate the rational use of these products with practices for conserving natural enemies.

Ecological relevance

Researchers claim that Trichopoda ypiranga has ecological relevance and can contribute to biological control strategies for Diceraeus melacanthus. They also indicate the need for further studies on biology, behavior, host specificity, and selectivity to agrochemicals. This data can guide the inclusion of the species in integrated pest management programs.

The study was developed by Suellen KA Barros, Camila S. de Oliveira, Rodrigo de VP Dios, Ana PM da Silva, and Rafael M. Pitta.

Further information can be found at doi.org/10.37486/2675-1305.ec08017