How to identify Leptodelphax maculigera and Dalbulus maidis

Leafhoppers of the families Cicadellidae and Delphacidae are common in grasses and form a recognized important group of insect vectors of viruses and mollicutes, causal agents of diseases in several plant species, including corn crops.

The corn leafhopper Dalbulus maidis is from the Cicadellidae family. They are phytophagous insects and are the most diverse group of Membracoidea (superfamily), with around 21 thousand described species. The African leafhopper (Leptodelphax maculigera) is from the Delphacidae family, a family of leafhoppers containing around 2 thousand species, distributed worldwide.

The Delphacidae family commonly occurs in monocotyledons (grasses, shrubs and trees), with the ability to be vectors of phytopathogens, mainly viruses. However, there are species that transmit phytoplasmas and cause diseases, especially in sugarcane and rice (Eumetopina flavipes, Javesella discolor, Nilaparvata lugens, Saccharosydne saccharivora). For example, the brown leafhopper (N. lugens) is a very destructive insect pest in rice, with 18 symbiotic bacteria described that can be transmitted.

Within the Delphacidae family, there are leafhoppers of the genus Leptodelphax, which, worldwide, have the following species: Leptodelphax dymas (Fennah 1961), Leptodelphax maculigera (Stal 1859) and Leptodelphax cyclops (Haupt 1927). In Africa, Leptodelphax dymas is responsible for the transmission of Napier grass stunt (NGS), which is a phytoplasma of the genus "Candidatus", extremely harmful to elephant grass crops. And, recently, Leptodelphax maculigera was identified as a transmitter of MRFV in cultivated plants, and potentially a vector of the stripe virus in corn crops in Brazil.

In Brazil, it was recently found in the states of Goiás, Rio Grande do Sul, Paraná, Santa Catarina, São Paulo and Mato Grosso do Sul, and in the state of Rio Grande do Sul, L. maculigera was verified in the municipalities of Cruz Alta, Passo Fundo and Santa Rosa. In these locations, it was captured in yellow adhesive traps.

This capture occurred in areas of tiguera corn, cultivated corn and wheat crops. This species shows its adaptability and has as hosts not only corn, but also kikuio grass (pennisetum clandestinum), sugar cane (Saccharum officinarum), setaria grass (setaria sphacelata), brachiaria (brachiaria sp.), elephant grass (Pennisetum purpureum), on weeds in bean and wheat crops and citrus orchards.

In this context, it is demonstrated that L. maculigera It is an oligophagous species, that is, it feeds on a relatively restricted number of host plants from different genera within the same family, and in this case the insect is associated with the poaceae family, economically important plants in Brazil.

However, the similarity with other species of leafhoppers such as Dalbulus maidis, can lead to misidentification of its occurrence in the areas - or non-detection. In this context, knowing some morphological characteristics of the African leafhopper can help in correct monitoring and avoid possible identification errors.

the species L. maculigera It has a straw color, hyaline wings and black eyes, and is 0,4 cm smaller when compared to D. maidis. The corn leafhopper (D. maidis) is characterized by dark dots on the head, while in the African leafhopper (L. maculigera) there is a dark spot on the clypeus (region located on the lower part of the head), characteristic of this species.

A striking feature that differentiates the African leafhopper from the corn leafhopper is the antenna. The African leafhopper has an antenna with a clearly visible dilated pedicel. The pedicel is close to the insertion of the antenna on the insect's head. The antenna D. maidis It does not have a dilated pedicel, being tapered throughout its entire length.

Another characteristic of the Delpachidae family, which can be used to differentiate the two species, is found in the third pair of legs (the furthest from the head), with tibiae with a mobile apical spur.

The occurrence of the African leafhopper has raised concerns regarding the imminent risk of it being an insect vector for the pathogens of corn stunt, that is, the red stunt phytoplasma (“Candidatus Phytoplasma asteris”, Subgroup 16SrI-B); the pale stunt spiroplasma (Spiroplasma kunkelii); the maize rayado fno virus (MRFV) and the striate mosaic virus (MSMV), all transmitted by Dalbulus maidis.

The work carried out to date has already indicated, through molecular analyses, that several specimens of the African leafhopper captured were infectious with MRFV in Rio Grande do Sul, Santa Catarina, Paraná and São Paulo. However, the possibility of infection in corn crops and the risks related to the bacteria still need to be confirmed.

In short, Leptodelphax maculigera It is a species of insect of the Delphacidae family, found in various regions of the world; it feeds on plant sap, mainly grasses. Therefore, it is necessary to observe the following aspects in order to create robust information and avoid creating unnecessary panic about the problem of the African leafhopper in corn crops.

1. Identify L. maculigera to understand the size of the problem in Brazil and what its percentage is in relation to D. maidis (main problem in corn crops)
2. Know the potential of L. maculigera as a bacteriophage in corn crops
3. Know its development in different hosts, being able to verify its possible adaptation to the corn cultivation system
4. Monitoring crops and symptoms with analysis to confirm infectivity in plants
5. Integration of management tactics D. maidis should also be implemented for areas with the presence of L. maculigera.

In this context, the African leafhopper is yet another pest capable of feeding on and causing damage to corn crops. Therefore, correct monitoring, adequate management and IPM techniques must be employed to minimize impacts on the productivity and quality of corn crops.

By Glauber Renato Stürmer, CCGL – Central Gaucha Cooperative Ltd.

Article originally published in issue 298 of Cultivar Grandes Culturas Magazine