First record of the rice root aphid, Rhopalosiphum rufiabdominale (Sasaki, 1899) (Hemiptera: Aphididae), in coriander in Puebla, Mexico

Coriander or cilantro, Coriandrum sativum L. (Apiaceae), is a plant used as an ingredient in dishes of Mexican cuisine. In 2017, Mexico exported around 64,000 tons to the United States and Canada, valued at more than US$47 million (SIAP 2019). Today, 6983 ha are cultivated, with Puebla being the largest producer with 3294 ha (SIAP 2021). Since 2018, technicians have reported the presence of an unknown type of aphid on the roots and base of cilantro. In February 2021, aphids were collected in Palmarito Tochapan, Quecholac, Puebla (N18.924975°, W97.644956°). The nymphs and adults were preserved in 70% ethyl alcohol. Using the keys of Blackman & Eastop (2006) and Peña-Martínez et al. (2017), the species was identified as the rice root aphid, Rhopalosiphum rufiabdominale (Sasaki, 1899). The rice root aphid is frequently found on species of Poaceae, Cyperaceae, and Rosaceae (Blackman & Eastop 2006). It has also been reported on cotton (Doncaster 1956), chili and aeroponic pumpkin (Etzel & Petit 1992), tomato and potato (Blackman & Eastop 2000), celery (Dara 2015), and hemp (Cranshaw & Wainwright-Evans 2020). Aldryhim & Khalil (1996) also reported the presence of R. rufiabdominale on C. sativum roots in Saudi Arabia. This report is the first record of the rice root aphid in Mexico affecting the cilantro crop. The collected individuals varied in coloring, ranging from orange in early instars to dark green in wingless adults (Fig. 1). In both cases, a reddish area was visible at the height of the cornicles. This pattern of coloring is distinguishable from Rhopalosiphum maidis (Fitch, 1856), which is bluish green and has dark spots at the base of the cornicles. However, they can be frequently confused with Rhopalosiphum padi (Linnaeus, 1758) because of the reddish coloring at the cornicles, but R. padi has six antennal segments, while R. rufiabdominale has five (Doncaster 1956). Aphid outbreaks can cause significant economic damage. Large populations feeding directly on the crop can cause a reduction in growth, yellowing, and leaf deformation. Some plants infested with rice root aphid exhibited yellowing and reduced growth (Fig. 1a). However, some of the specimens were collected from plants that were not yellowing and were apparently healthy. The highest incidence of this insect in Puebla occurs from December to March, when precipitation is low. The cryptic habit of this aphid makes its detection difficult, and if initial infestations are not detected on time, this can lead to high densities that seriously affect the crop. The purpose of this note is to inform of the presence of R. rufiabdominale on cilantro in Puebla, Mexico, so that growers and field technicians can take timely measures, such as frequent monitoring when there are optimal conditions for development of this pest and management of alternate hosts. In addition, it is necessary to generate information on alternative tools that would allow us to give sound advice for control of this pest.