Abstract The corn leafhopper Dalbulus maidis (DeLong) (Hemiptera: Cicadellidae), transmits three important plant pathogens that adversely affect corn crop and ranges from the USA to Argentina. The vector has a rich natural enemy complex that generates high levels of parasitism, but its populations are persistent and prevalent. We characterized the oviposition sites of D. maidis on young corn plants in order to verify the hypothesis that the vector has an oviposition strategy for mitigating parasitism. Oviposition locations on plants were assessed in the laboratory and eggs within corn plants were exposed to natural parasitism in a cornfield. Eggs were located mostly laid in the unfolded leaves and were attacked by five parasitoid species. Parasitism was significantly affected by the class of leaf and the position of the egg in the leaf. Anagrus virlai Triapitsyn was the most abundant parasitoid species, which emerged significantly higher in the basal blade than other species. Our results suggest that leafhoppers minimize egg parasitism by laying their eggs within concealed locations on the plant.

The fall armyworm (FAW) is the most important threat to corn crops in Argentina, and there exists very little up-to-date information on its actual pest status because the available literature was published more than 20 years ago. Therefore, field surveys were carried out in the northeast of Argentina, in order to establish the attack rates and injury levels of the pest in relation to the crop phenology. The study was carried out at two localities: Colonia Benítez, an agricultural region, and Tapenagá, a cattle-raising area. At each site two 1-ha plots were sown either with a Bt-corn expressing Cry 1F protein or with an untransformed corn germplasm. Optimal and late sowing was assayed and FAW larval abundance, relative age composition, attack rates and level of damage to corn were recorded. At the moment of the field experiments, Bt-corn was not affected by FAW larvae. However, untransformed germplasms were severely affected by FAW larvae, with an average of attacked plants of 18% or more. In contrast to data obtained 30 years ago, higher values of FAW density were registered. Levels of damage to corn plants were higher after the V4 stage. It was found that the sowing date affected the infestation levels and early seeding avoided high armyworm densities that develop later in the season; in northern Argentina, this was only relevant in agricultural areas.

El cogollero es la plaga más importante del maíz en Argentina, siendo escasa y desactualizada la información sobre su estatus como plaga en los últimos 20 años. Se llevaron a cabo estudios de campo a fin de establecer las tasas de ataque y los niveles de daño de la plaga en relación con la fenología del cultivo en el noreste de Argentina. El estudio se realizó en dos localidades: Colonia Benítez, zona agrícola, y Tapenagá, zona ganadera. En cada localidad se sembraron dos parcelas de una hectárea, una con maíz transgénico expresando la proteína Bt Cry 1F y la otra con su correspondiente isogénico no transformado. Se registraron para dos fechas de siembra: cantidad de larvas, composición relativa de edades, tasa de ataque y nivel de daño al cultivo. En el momento del ensayo de campo, el maíz Bt no fue afectado por la plaga; sin embargo, el isogénico (sin gen Bt) fue atacado con una media superior al 18% de plantas dañadas. Comparando con datos obtenidos hace 30 años en esta región, se obtuvieron mayores valores de densidad de larvas/planta. Los niveles de daño fueron mayores después de V4. La fecha de siembra incide en los niveles de infestación: siembras tempranas evitan las altas densidades del cogollero que se desarrollan durante el verano, pero para la región estudiada esto solo fue relevante en la zona agrícola.

Diatraea saccharalis (Fabr.) is considered the key pest of sugarcane crops in the Argentine northwest. The earwig Doru luteipes (Scudder) develops high populations on sugarcane, and in other regions it was depicted as a significant predator of diverse pest in corn, cotton, and cabbage crops. The aim of this contribution is to inform about different biological parameters of this Dermaptera, and to assess the predatory capacity of its nymphs by means of the estimation of consumption rates using Diatraea saccharalis eggs. Both field and laboratory observations were carried out. In the latter, 50 neonate nymphs were confined in glass tubes and 100 sugarcane borer eggs were provided daily. Information on different behavioral aspects is provided. In field conditions, the sex proportion is approximately 1:1; an average of 31 eggs were laid, and the emergence rate reached 95%. Egg incubation is complete within a range of 6-10 days, and pre-imaginal development has a mean duration of 37.6 days. Throughout the four nymphal instars, a single individual could consume an average of 591.3 sugarcane borer eggs. The potential implication of the given information in applied sugarcane borer control methodologies is discussed.

Diatraea saccharalis (Fabr.) es considerada la principal plaga de la caña de azúcar en el noroeste argentino. El dermáptero Doru luteipes (Scudder) desarrolla importantes poblaciones en dicho cultivo y ha sido descrito como predador de plagas en maíz, algodón y coles. El objetivo de este trabajo fue brindar información sobre algunos aspectos biológicos y estimar la capacidad de predación de las ninfas de Doru luteipes, a través de la tasa de consumo de huevos de Diatraea saccharalis. Se realizaron observaciones de campo y ensayos de laboratorio, en estos últimos se colocaron individualmente en tubos de ensayo, 50 ninfas de D. luteipes recién eclosionadas y se les ofrecía diariamente cien huevos de la plaga. La proporción de sexos de D. luteipes en campo fue de aproximadamente 1:1 y sus posturas presentaron una media de 31 huevos, con una tasa de emergencia cercana al 95%. El período de incubación se prolongó entre 6 y 10 días y el desarrollo de los estadios ninfales promedió los 37,6 días. Las ninfas pasaron por cuatro estadios y consumieron una media de 591,3 huevos de D. saccharalis. Estos resultados sugieren que D. luteipes desempeña un papel importante en el control natural de las poblaciones de D. saccharalis, por lo tanto, su presencia debería tenerse en cuenta al diseñar estrategias para controlar esta plaga.

Eudorylas schreiteri (Shannon) é registrada pela primeira vez como endoparasitóide da cigarrinha do milho Dalbulus maidis (DeLong & Wolcott) no norte da Argentina. Uma tabela das espécies neotropicais de pipunculídeos com hospedeiros conhecidos é apresentada.

The big-headed fly Eudorylas schreiteri (Shannon) is recorded for the first time as an endoparasitoid of the corn leafhopper Dalbulus maidis (DeLong & Wolcott) in Northern Argentina. A table of known Neotropical pipunculid-host associations is presented.

Se estudiaron los parasitoides de la chicharrita del maíz, Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Auchenorrhyncha) en la provincia de Tucumán, Argentina. Las chicharritas atacadas por Dryinidae (Hymenoptera: Chrysidoidea) fueron colectadas en campos de maíz entre dic 2003 y abr 2005. Se obtuvieron driínidos de tres especies diferentes: Gonatopus caraibicus (Olmi), Gonatopus contortus Olmi, y G. moyaraygozai Olmi. Se cita por primera vez a G. moyaraygozai en Argentina, y se describe al macho de dicha especie. Se registra por primera vez en campo la asociación parasitoide-hospedador de G. caraibicus y D. maidis; además, se mencionan por primera vez a G. contortus y G. moyaraygozai como parasitoides de la chicharrita del maíz. Se calculó la tasa de parasitoidización de G. moyaraygozai en campo.

The parasitoids of the Corn Leafhopper, Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Auchenorrhyncha) were studied in Tucumán Province, Argentina. Leafhoppers parasitized by Dryinidae (Hymenoptera: Chrysidoidea) were collected in cornfields from Dec 2003 to Apr 2005. Dryinid adults belonging to three species, Gonatopus caraibicus (Olmi), Gonatopus contortus Olmi, and G. moyaraygozai Olmi, were obtained. G. moyaraygozai is quoted for the first time in Argentina, and the male is described for the first time. This contribution presents the first field host-association record for G. caraibicus and D. maidis; in addition, G. contortus, and G. moyaraygozai are cited for the first time attacking Corn Leafhopper populations. Data on the parasitization rate by G. moyaraygozai are given.

Os parasitoides da cigarrinha do milho, Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Auchenorrhyncha) foram estudados na província de Tucumán, Argentina. As cigarrinhas atacadas por Dryinidae (Hymenoptera: Chrysidoidea) foram colectadas em cultivos de milho entre dezembro de 2003 e abril de 2005. Foram obtidos dryínidos de três espécies diferentes: Gonatopus caraibicus (Olmi), Gonatopus contortus Olmi e Gonatopus moyaraygozai Olmi. G. caraibicus, anteriormente obtido de D. maidis sómente em laboratório, foi criado também em campo. Pela primeira vez G. contortus e G. moyaraygozai são citados como parasitoides de D. maidis. De G. moyaraygozai, citado pela primeira vez em Argentina, foram obtidos ambos os sexos; a descrição do macho, anteriormente desconhecido, é feita pela primeira vez. A taxa de parasitismo de G. moyaraygozai foi avaliada em campo.

The objective of this contribution is to mention Gonatopus chilensis Olmi (Dryinidae: Gonatopodinae) as a new host for the encyrtid Cheiloneurus cupreicollis Ashmead, and enlarge the geographic distribution of the parasitoid to Catamarca province (Santa María).

El objeto de la presente contribución es informar sobre el comportamiento parasitoide del encírtido Cheiloneurus cupreicollis Ashmead sobre Gonatopus chilensis Olmi (Dryinidae: Gonatopodinae), y ampliar su distribución geográfica a la provincia de Catamarca (Santa María).