Occurrence of Aetalion reticulatum (Linnaeus) (Hemiptera: Aethalionidae) on Dipteryx alata Vogel (Fabaceae) in Minas Gerais, Brazil

The baruzeiro or baru (Dipteryx alata Vogel) is a tree species native to Brazil that is known for its production of edible nuts with high nutritional value. However, little is known about the insects associated with this forest species. Therefore, this study aims to document the occurrence of leafhoppers on baruzeiro trees in the state of Minas Gerais, southeastern Brazil. We therefore examined baruzeiro plants in an afforestation plot at the Universidade Federal de Uberlândia (18°43’33”S; 47°31’31”W) in August 2020, located in the municipality of Monte Carmelo, Minas Gerais. The leafhopper species was identified as Aetalion reticulatum (Linnaeus) (Hemiptera: Aethalionidae). The ant species Camponotus crassus Mayr (Hymenoptera: Formicidae) was found to feed on the honeydew released by leafhoppers, demonstrating facultative mutualism between the species. This is the first report of A. reticulatum on D. alata in Minas Gerais.

The baruzeiro can be used for several purposes such as providing shade, forage, wood, nutrient cycling, plant litter decomposition, human food, and is a potential candidate for commercial cultivation (Sano et al. 2006). According to FernandeS et al. (2010), the toasted baru nut has been used in human diets due to its high protein value and pleasant taste. In addition, oil can be extracted from lipid-rich nuts (FernandeS et al. 2010).
The baru and its products are harvested via extractive activities in its natural habitat. However, the dearth of information about its biology and management makes it difficult to carry out these activities in a sustainable manner (SouSa et al. 2011). Likewise, little is known about the insect fauna associated with D. alata, especially with respect to potential pests that may compromise its development and propagation.
There have been reports of fruit pulp damage by insect species, mainly belonging to the orders Coleoptera and Lepidoptera (Carvalho 2003;Sano et al. 2006 This study aims to document the occurrence of leafhoppers in baruzeiros in the state of Minas Gerais, Brazil. To this end, in August 2020, three-year-old plants of D. alata about 2.5 meters in height were examined using a ladder. The trees are part of an afforestation plot at the Universidade Federal de Uberlândia, Monte Carmelo Campus (18°43'33"S; 47°31'31"W), in the municipality of Monte Carmelo.
The baruzeiro plants on the afforestation plot have vegetation nearby. To the west, the vegetation is composed of an orchard of herbaceous plants, located about 15 meters away. To the east, the baruzeiros are bordered by an asphalt road about five meters away. To the north and south, the vegetation consists of creeping plants with a predominance of Poaceae species that receive regular mechanical cutting.
The municipality of Monte Carmelo is located in the mesoregion of Alto Paranaíba and is situated at an altitude of about 890 m, with vegetation typical of the Cerrado biome. The mesoregion is located in the basin of the Paranaíba River, and the soils are predominantly red latosols. The region is characterized by a seasonal climate of the type Aw according to the Köppen climate classification with two well-defined seasons: hot and rainy summer and cold and dry winter. The average temperature is 20.7 °C, and the average annual rainfall is 1,569.1 mm (Prado Júnior et al. 2012).
In August 2020, from 1 pm to 4 pm, each plant was observed in 15 min intervals for a total sampling effort of 90 min per plant. Two baruzeiro plants, about eight meters away from each other, were examined. In one of them, oviposition, nymphs, and adult leafhoppers were observed on all doi:10.12741/ebrasilis.v13.e930 branches in varied numbers ( Figure 1A). Ants feeding on honeydew released in the feces of the leafhoppers were also observed ( Figure 1A). The presence of the leafhopper species in the nearby vegetation was not verified.
The specimens were photographed in situ with an Olympus SP-620UZ 16MP camera. Adult specimens and nymphs of leafhoppers and ants were collected with tweezers, packed in labeled flasks containing 70% alcohol, and then taken to the Laboratório de Entomologia Florestal (LAENF) of the Monte Carmelo Campus.
The specimens were mounted with entomological pins in the laboratory, and identification was carried out to the lowest possible taxonomic level using an SZ40 Marca-Physis stereoscope microscope. The taxonomist Dr. Wilson The leafhopper species was identified as A. reticulatum ( Figures 1A and 1B), and the ant species was identified as Camponotus crassus Mayr (Hymenoptera: Formicidae) ( Figure  1A) on one of the two baruzeiro plants analyzed ( Figure 1C).
Aetalion reticulatum is widely known as honeydew-producing leafhopper since it is of economic importance for a diversity of fruit species. Adults measure about 10 mm in length, have a rust-brown coloration, and the ribs of the wings are protruding and greenish. Females oviposit masses of up to 100 eggs enveloped in a brown-gray choleretic substance on plant branches and/or fruit peduncles. The incubation period of the eggs is about 30 days, during which the female protects the spawning eggs with her body ( Figure 1B). The nymphs have a grey coloration with red striations, and this stage lasts approximately 45 days. Both nymphs and adults suck the sap from the plants, damaging the development of fruits and sprouts; heavy infestations can cause the death of the plant (Gallo et al. 2002).
The honeydew-producing leafhopper is polyphagous and has been found in a variety of plants. In Brazil, these include a number of economically important native forest species, such as D. alata in Brasília (CaStro et al. 2019), the "sombreiro" Clitoria fairchildiana Howard (Papilionoideae) in the state of São Paulo (oda et al. 2009), the açaí palm Euterpe oleracea Martius (Arecaceae) in the state of Acre (SantoS et al. 2015), and the "corticeira" Erythrina speciosa Andrews (Fabaceae) in the state of Rio de Janeiro (ZanunCio et al. 2015). This species has also been reported on exotic species used for forestry in Brazil, such as the silk oak Grevillea robusta (Cunn) (Proteaceae) in the state of São Paulo (Santana et al. 2005), in the eucalyptus Eucalyptus cloeziana F. Muell. (Myrtaceae), in Minas Gerais (MeneZeS et al. 2012), and the teak Tectona grandis Linn. F. (Verbenaceae), also in Minas Gerais (tavareS et al. 2018). Since all developmental stages of A. reticulatum (eggs, nymphs, and adults) have been found in D. alata, these findings indicate that this host is suitable for the development of the insect. The fact that A. reticulatum was found on only one of the baruzeiro plants analyzed may be related to possible resistance or pseudo-resistance by the non-infested plant. However, these factors were not evaluated in this study.
Aetalion reticulatum has already been found in mutual association with ant species of the genus Camponotus in several cultivated areas in Brazil (Santana et al. 2005;SantoS et al. 2015;ZanunCio et al. 2015;CaStro & Maltovão 2019a, 2019b; this corroborates the results of this study, in which the presence of C. crassus foraging the honeydew expelled by the leafhoppers was verified, with the ants protecting the leafhopper colony from natural enemies. This type of interaction was observed by rando & liMa (2010), who found Camponotus rufipes (Fabr.) (Hymenoptera: Formicidae) and C. crassus in colonies of A. reticulatum in the clove basil Ocimum gratissimum L. (Lamiaceae). These authors observed that the ant species used their antennae and tarsus to stimulate the abdomen of the leafhoppers, causing them to expel the honeydew droplets from which they fed.