The habitat and adult host plants of 3 Ocoaxo species (Hemiptera: Cercopidae) are reported for the first time. In addition, their possible link to a disorder of forest pines we called “pine decline” in Mexico is discussed. The distribution of Ocoaxo varians (Stål), Ocoaxo assimilis (Walker), and Ocoaxo near fowleri (Lallemand) is described based on museum collection specimens and field collections performed during 2015.
In Italy and Spain, the spittlebug Haematoloma dorsatum (Ahrens) (Hemiptera: Cercopidae) causes severe damage to natural and planted forest trees of the genera Cedrus (Pinaceae), Cupressus (Cupressaceae), Juniperus (Cupressaceae), Picea (Pinaceae), and Pinus (Pinaceae) (Roversi & Baccetti 1994; Cobos 1995). In America, there are reports of adult males of Prosapia species (Hemiptera: Cercopidae) feeding on trees, including Ilex haberi (Lundell) W. J. Hahn, I. cornuta Lindl. & Paxton, and I. opaca Soland. ex Aiton (Aquifoliaceae), and of Iphirhina quota (Distant) (Hemiptera: Cercopidae ) feeding on Bourreria costaricensis (Standl.) A. H. Gentry (Boraginaceae) (Peck 1998). Whereas there are reports of North American aphrophorid spittlebugs (Hemiptera: Aphrophoridae) feeding on natural and planted forest trees as pests (Wilson 1991), there are no reports of pine-feeding Cercopidae in either North or South America.
In 2008, adult spittlebug feeding damage was observed in Mexican forests of Pinus oaxacana Mirov. nearby Nicolás Bravo (Puebla State, Mexico) and on Pinus chiapensis (Martínez) Andresen in Santa Ana Cuauhtémoc (Cañada region, Oaxaca State, Mexico) (Queyla Beteta Santiago, personal communication). The impacted area and economic damage, however, were not quantified. Subsequently, a new spittlebug outbreak was reported in Mar and Jun 2015 in the municipalities of Tetela de Ocampo, Aquixtla, and Zacatlán de las Manzanas (State of Puebla, Mexico). Approximately 3,000 to 3,500 ha were afflicted. The damage was related to a symptomatology that we called “pine decline” associated with populations of adult spittlebugs resting, feeding, and mating on the foliage of Pinus trees. Nymphs were never found on those trees or on herbaceous plants in the understory.
Symptomatology of pine decline begins with drying of pine needle tips (Fig. 1A), descending down to the base of the needles. The foliage becomes yellowish, orange, or brown (Fig. 1B), and then the needles fall. These symptoms are similar to those caused by H. dorsatum (Roversi & Baccetti 1994; Cobos 1995). Symptoms occur in the middle of the rainy season when trees take on the characteristic colors; however, trees recover their foliage at the beginning of the next rainy season. This phenomenon was observed 3 times in the last years in the 3 aforementioned municipalities, but after the 3rd time, many of the trees did not recover and they died. Nevertheless, at Santa Ana, the P. chiapensis trees recovered their foliage and none died because spittlebug populations naturally declined. At Nicolás Bravo, the P. oaxacana trees recovered, probably due to an outbreak of the entomopathogenic fungus Metarhizium anisopliae (Metsch.) Sorokin (Clavicipitaceae).
In Jun through Oct 2015, we collected insects from 3 localities of Puebla State: “Acatlán” (19.85825°N, 97.83385°W) and “Rancho Alegre” (19.84278°N, 97.85611°W), both sites in Tetela de Ocampo, and “Km 68 Carretera Federal Zacatlán-Apizaco” (19.90189°N, 97.95861°W) in Zacatlán de las Manzanas. Adult spittlebugs were found on trees of Pinus pseudostrobus Lindl,, Pinus patula Schiede ex Schltdl. & Cham., and Pinus sp., and 1 adult was feeding on Rubus sp. (Rosaceae). Many insects were observed in a feeding position with forelegs extending out into the air like the Central American species Mahanarva costaricensis (Distant) (Hemiptera: Cercopidae) (Carvalho & Webb 2005) on Heliconia spp. (Heliconiaceae) (Fig. 2A, B). Mating pairs were also observed, confirming the presence of both males and females. Adults inserted the stylet into various sites on the needles selected for feeding (Fig. 2C). At abandoned feeding sites, the damage persisted, possibly due to the phytotoxic effects of salivary substances (Fig. 2D).
Several authors have described chlorosis in pasture grasses caused by the toxic effects of cercopid saliva (Taliaferro et al 1967; Valério & Nakano 1992). On Brachiaria decumbens Stapf (Poaceae), for instance, symptoms of damage due to 1 h of exposure to cercopid feeding was first observed 3 d later, having the greatest expression 23 d later (Valério & Nakano 1992). Cobos (1995) reported that adults of H. dorsatum stayed only a short time on Pinus pinaster Aiton after damage was observed, when adults had completed their flight period and disappeared under field conditions. This phenomenon could be similar to that found in Puebla and Oaxaca caused by the detected cercopids.
Observation and collecting efforts resulted in the detection of 3 spittlebug species in the cercopid genus Ocoaxo on Pinus host trees. The first, at Nicolas Bravo in 2008, was identified as Ocoaxo assimilis (Walker). Another group of insects collected on Pinus trees in the same year, close to the road between Oaxaca City and Pochutla City, was identified as Ocoaxo varians (Stål). Insects collected in 2015 did not match either of the aforementioned species based on external morphology and male genitalia. This additional species is now under study and is called Ocoaxo near fowleri (Lallemand).
Based on specimens deposited in the Colección Nacional de Insectos of the Instituto de Biología, UNAM (CNIN) and the Colección de Insectos del Colegio de Postgraduados-Montecillo (CEAM), the distribution of Ocoaxo species in Mexico by state is as follows: O. varians in Guerrero, Oaxaca, Puebla, Tlaxcala, and Veracruz; O. assimilis in Oaxaca, Puebla, and Veracruz; Ocoaxo near fowleri in Ciudad de México, Coahulia, Edo. México, Michoacán, Nuevo León, Oaxaca, Puebla, Querétaro, and San Luis Potosí. All 3 species have been collected in the states of Oaxaca and Puebla, but never at the same time.
It is necessary to establish the true relationship between Ocoaxo species and pine decline, as their distributions overlap with pine forests in many states of Mexico. Nast (1950) and Fennah (1968), authors who have worked most on the genus Ocoaxo, did not discuss their biology and ecology. In fact, there are no known observations in the literature of Ocoaxo host plants. It is clear now that there are some spittlebug species associated with pine forests. However, specific host plants for nymphs are unknown, despite the extensive search for this life stage in 2015 (Jun to Dec 2015). It may be that we did not find the nymphal stage of Ocoaxo near fowleri because our efforts were focused on pines and the understory plants. We did find nymphs on grasses but these belonged to the species Prosapia ignifera Hamilton, Prosapia teapana Fennah, and Prosapia inferens (Walker) (Hemiptera: Cercopidae), and we did not see adults of Ocoaxo near fowleri emerging from any spittlemasses.
We thank Cristina Mayorga, co-curator at the Colección Nacional de Insectos, Instituto de Biología, UNAM (CNIN) for the loan of Ocoaxo species materials; Thomas Atkinson for reviewing the manuscript; Luis Orlando López-Zuñiga at NCSU for sending literature relevant to this scientific note. This research was funded in part by the Consejo Nacional de Ciencia y Tecnología (CONACYT), grant #308701.