Corn leafhopper

The corn leafhopper, a hemipteran insect of the family Cicadellidae, is an increasingly important pest of corn in several South American countries including Brazil and Argentina.  Historically it has only been a minor pest of corn, causing minor damage through direct feeding. However, as a vector of corn stunt spiroplasma (CSS), maize bushy stunt phytoplasma (MBSP); and Maize rayado fino virus (MRFV), its status as a pest has increased with increasing intensity of corn cultivation and new growing practices.

Corn plants are most vulnerable after seedling emergence, but reduction in corn yield can still occur through leafhopper attacks during the vegetative period. Foliar and seed applied insecticides are the principal control method for this pest, with multiple applications being made during the vegetative period to prevent virus transmission.

SUSCEPTIBILITY TEST METHOD

• No validated IRAC Method (July, 2024)
• Machado et al (2024) provides a description of a leaf-dip bioassay based on IRAC Method 19 with some adaptation.

Corn leafhopper resistance profile

High levels of resistance (>100-fold) to pyrethroid and neonicotinoid insecticides have been recorded in populations of Dalbulus maidis collected across several Brazilian states, and therefore resistance to these insecticide classes can be considered as widespread in Brazil.  A low level of resistance (<20-fold) to carbamate insecticides was also noted in one population collected from Bahia State.

Resistance to other classes of chemistry may also be present in Brazilian populations of Dalbulus maidis, although there´s no published data yet.

Pyrethroid and Neonicotinoid resistant populations of Dalbulus maidis may also exist in other South American countries, but there is no currently published data to verify the presence or absence of resistance.