Ernesto Cerna-Chávez

Natural Enemies of the Fall Armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) in Coahuila, México

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) is the main insect pest of corn and other crops in Latin America (Hernandez-Mendoza et al. 2008). The larvae cause severe damage in all phenological stages of the plant (Villa-Castorena & Catalan-Valencia 2004). Control has been with synthetic pesticides; however, this method is inefficient and causes chronic poisoning to growers in Mexico due to incorrect use (Tinoco & Halperin 1998). This has led to the search of other options to manage S. frugiperda including use of natural enemies. Twenty two species of natural enemies have been reported in various parts of Mexico (Molina-Ochoa et al. 2004). Our objectives were to identify the natural enemies of the FAW and the level of parasitism in the area of Buenavista, Coahuila, Mexico. Twelve weekly samplings of FAW larvae were made from Jul to Sep in corn fields infested with FAW at the “El Bajio” Experimental Station of the Universidad Autonoma Agraria Antonio Narro (25°23’N, 101°00’W). On each sampling date, 100 larvae of each of the first 3 instars, were randomly collected and placed in 1-oz. (29.6 mL) plastic cups containing an artificial diet (Southland Products Incorporated) and incubated in a bioclimatic chamber at 25 ± 2°C, a photoperiod of 12:12 L:D h, and 50-60% RH. Parasitoids were recovered, tagged, and preserved in 70% alcohol for further mounting and identification with taxonomic keys (Triplehorn & Johnson 2005). Confirmations of identifications were made by Dr. Alejandro Gonzalez Hernandez (Departamento de Ciencias Biologicas, Universidad de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon, Mexico). Entomopathogenic fungi from dead larvae were cultured in moist chambers and purified in an artificial medium of potato dextrose agar (PDA) complemented with corn liquor for Beauveria bassiana (Balsamo) Vuilleiman and V8-Agar for Nomuraea rileyi Farlow (Samson), at a pH of 6.0. The purified entomopathogens N. rileyi and B. bassiana were identified according to their microscopic and macroscopic characteristics (Barnett 1986). Larvae with symptoms of viral infection were processed by taking samples of occlusion bodies (OBs) and dying the preparations with 0.4% Giemsa stain. Identification was made at the Parasitology Dept., based on the OBs that showed polyhedric characteristics of the nucleopolyhedrovirus group (NPV). Parasitism (as a percentage) was calculated based on the total number of larvae of S. frugiperda that were positive for parasitoids and entomopathogens divided by the total number of FAW larvae collected. Altogether, 1200 larvae of S. frugiperda were collected. Parasitoids and parasites such as Hymenoptera (Ichneumonidae, Braconidae, Eulophidae) and Diptera (Tachinidae), as well as entomopathogens (Nucleopolyhedrovirus, N. rileyi and B. bassiana ) killed 526 larvae (43.83%). Sixty-eight (5.7%) died from unknown causes and the remainder of the larvae (674) reached adulthood (Table 1). Mortality of some parasitoids (132, 11% of the total) occurred before emergence of the adults. Parasitoids caused 35.25% parasitism of the larvae (Table 1). Armenta et al. (2008) reported a parasitism rate of 32.2% for Sonora, Mexico. Braconidae was the best represented with 261 specimens (21.75% of total parasitism), in which 257 were Chelonus insularis (21.42%), Ch. cautus (0.25%) and Ch. sonorensis (0.08%) (Table 2). Molina-Ochoa et al. (2004) reported similar percent of parasitism in Michoacan Mexico (45.3%). Ichneumonidae showed low levels of parasitism (1.17%). This information is similar to that reported by Murua et al. (2006). Pristomerus sp. presented a low level of parasitism (0.42%), similar to the 0.24% reported by Ruiz-Najera et al. (2007) (Table 2). Chelonus sonorensis showed a parasitism level of 0.75%, contrasting with data from Cruz-Sosa (2007), who found it to be the most abundant species in Oaxaca, Mexico. Euplectrus plathyphenae (Eulophidae) showed 0.42% parasitism. Only 0.92% parasitism by tachinid flies was found in the present study. Mortalities caused by the entomopathogens, NPV, N. rileyi , and B. bassiana were of 2.0, 0.75 and 0.08%, respectively (Table 2).

Genetic variation and the performance of a mass-reared parasitoid, Trichogramma pretiosum (Hymenoptera: Trichogrammatidae), in laboratory trials

During mass rearing, adaptation of biological control agents to the rearing environment is a potential problem. Using the parasitoid wasp Trichogramma pretiosum, the performance of 26 highly inbred lines, five composite ‘populations’ (created from the inbred lines) and one insectary‐reared population was compared using fertility life tables. Of the composite populations, three were created with maximal and identical genetic variation as a mixture of all 26 inbred lines, but these were then reared for a different number of generations (2, 6 or 17) before their performance was measured. The remaining two composite populations were created based on the performance of the individual inbred lines: one was a combination of two inbred lines with a high intrinsic rate of natural increase (rm), ‘high rm’; and the other was a combination of two lines with a ‘low rm’. High and low rm populations were reared for two generations prior to testing. Parameters measured were fertility, longevity and sex ratio. We found no difference between the maximally variable population reared for two generations and the ‘high rm’ population (rm = 0.285 and 0.282, respectively). ‘Low rm’ was the population with the lower performance (rm = 0.255). Genetically variable population reared for two generations for 48 h produced significantly more offspring than the populations reared for 6 and 17 generations. Hybrid population derived from the high‐rm lines did significantly better than that derived from the low‐rm lines. Low‐performance populations become more male based than high performance at 48 h. The potential benefits to improve populations performance using inbred lines for mass rearing are discussed.

Insecticidal Effect of Plant Extracts on Bactericera cockerelli (Hemiptera: Psyllidae) Nymphs

Abstract. Potato psyllid, Bactericera cockerelli (Sulcen), nymphs were treated with extracts of Annona muricata L., Carica papaya L., Euphorbia dentate Michx, Thuja occidentalis L., Sapindus saponaria L., and Azadirachta indica A. Juss. (neem) as a commercial check in the laboratory. At 72 hours, most potato psyllid nymphs died (98 and 100% mortalities) from A. muricata extract from seeds, at concentrations of 2,500 and 5,000 ppm, respectively, followed by A. indica oil that caused 91 and 100% mortality at concentrations of 2,000 and 2,500 ppm, respectively. A. muricata seed extract was the most effective insecticide in the study.

Population variability of Spodoptera frugiperda (Lepidoptera: Noctuidae) in maize (Poales: Poaceae) associated with the use of chemical insecticides

Summary The objective of this research was to determine the genetic variability of Spodoptera frugiperda Smith & Abbot (Lepidoptera: Noctuidae) larvae from populations collected on maize (Poales: Poaceae) crops from several locations (Sinaloa, Jalisco, Coahuila, and Durango) in Mexico grown under various types of pest management using inter-simple sequence repeats (ISSR) type molecular markers. These ISSR markers amplified 105 loci, with 92.59% being polymorphic, which genetically characterized these populations and related this variability with factors such as pest control management. The most divergent population was from Tlajomulco, Jalisco. This location had the most intense use of chemical insecticides with diverse modes of action, which may account for much of the difference in genetic variability observed among sites in this study.

Efecto de Insecticidas Sobre la Mortalidad y Depredación de Chrysoperla carnea (Neuroptera: Chrysopidae)

Resumen. Los agentes de control biológico, juegan un papel sustancial en la disminución del número poblacional de muchas especies de insectos plaga. Sin embargo, el método químico es el más usado en los diferentes esquemas de producción. Por lo que la combinación del control biológico con el uso de plaguicidas es la piedra angular para el control integrado de plagas. Por lo tanto es esencial conocer los efectos letales y subletales de los insecticidas sobre los enemigos naturales para maximizar la compatibilidad entre estas dos tácticas. Para ello se determinó la CL50 de los insecticidas abamectina, bifentrina, endosulfan, imidacloprid, y profenofos sobre Chrysoperla carnea (Stephens) y se estimó su efecto sobre el consumo de ninfas de Bactericera cockerelli. Los resultados muestran que abamectina, bifentrina y endosulfan fueron menos tóxicos para C. carnea y no afectaron el consumo promedio de ninfas de la plaga. En contraste profenofos e imidacloprid resultaron altamente tóxicos para este depredador y además redujeron el consumo promedio de ninfas de B. cockerelli. Por consiguiente los insecticidas abamectina y bifentrina, se recomiendan para uso junto con liberaciones de Chrysoperla carnea en sistemas de manejo integrado de plagas.

Respuesta Funcional de Chrysoperla carnea en Ninfas de Estadio Inicial de Bactericera cockerelli

Resumen. El tipo de respuesta funcional que presentan los agentes de control biológico sobre sus presas en laboratorio puede utilizarse para inferir los mecanismos básicos de la interrelación depredador-presa en condiciones de campo. En este estudio se comparó el tipo y los parámetros de la respuesta funcional de los tres estadios larvales del depredador Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) sobre ninfas N1–N2 de la plaga Bactericera cockerelli (Sulc) (Hemiptera: Triozidae). El tercer estadio larval del depredador consumió más ninfas comparado con el primero y segundo estadio. Los análisis de regresión logística revelaron respuesta funcional tipo II para el primero y segundo estadio larval de C. carnea sobre B. cockerelli (P1 < 0), pero el tercer estadio larval presentó respuesta tipo III (P1 > 0). Los valores del coeficiente de ataque (a) para el primero y segundo estadio no fueron diferentes, sin embargo los valores del tiempo de manipuleo (Th) fueron significativamente diferentes. Esto sugiere que ambos estadios tienen igual capacidad de descubrimiento de la presa, pero el segundo estadio larval tarda menos tiempo en manipularla. Los resultados de esta investigación sugieren el uso de larvas L1 de C. carnea cuando predomine una mayor cantidad de ninfas N1–N2 en los cultivos, con lo cual se podrían provocar una mayor reducción sobre las poblaciones de la plaga.

Plant Oils to Control Sitophilus zeamais Motschulsky1

Abstract. The maize weevil, Sitophilus zeamais Motschulsky, is the most important pest of stored maize, Zea mays L. The pest causes estimated losses of 5–10% worldwide. Oil extracts from plants show promise to control maize weevil with important advantages over conventional insecticide, such as non-toxicity to humans, biodegradability, and ecosystem safety. The objective of this research on maize weevils in laboratory conditions was to determine the insecticidal effect of 10 plant oils: garlic, Allium sativum L.; cinnamon, Cinnamomum verum J.; hot pepper, Capsicum annuum L.; clove, Syzygium aromaticum L.; mint, Mentha piperita L.; black pepper, Piper nigrum L.; rosemary, Rosmarinus officinalis L.; rue, Ruta graveolens L.; thyme, Thymus vulgaris L. and allyl (commercial product). Residual film was used to test plant oils at five concentrations: 9,000, 7,000, 5,000, 3,000, and 1,000 ppm. The number of weevils killed was counted at 72 hours, and treatment means were compared using a Tukey multiple separation test. PC-Probit analysis determined LC50 and LC95. Most weevils, 52.47 and 60.38%, were killed by garlic and black pepper oils, respectively; at 9,000 ppm; fewer than 50% were killed with the other plant oils. Use of garlic and black pepper oil might be an alternative method to manage this insect pest in stored maize.

Efecto de Hongos Entomopatogenos Sobre Larvas de Mosca Sierra (Monoctenus sanchezi Smith) 1

Abstract. Monoctenus sanchezi is a sawfly of economic importance in forest management because of damage to the foliage of white cedar. Mortality by entomopathogenic fungi Metarhizium anisopliae, Beauveria bassiana, and Trichothecium sp. on M. sanchezi larvae was 98, 60, and 36% on the sixth day. Metarhizium anisopliae may be an alternative for biological control of the sawfly in México.

Umbrales de Desarrollo de Tamarixia triozae1 Parasitoide del Psílido de la Papa2

Resumen. Tamarixia triozae (Burks) es un ectoparasitoide de ninfas del psílido de la papa, Bactericera cockerelli (Sulc), con niveles de parasitismo en el campo hasta del 85% que además se alimenta sobre su hospedero, lo que contribuye a ser un potencial agente de control biológico. Con el fin de determinar los requerimientos térmicos y las temperaturas efectivas para el desarrollo de T. triozae se estimaron los grados días de desarrollo (GDD) que se requieren para completar el ciclo de vida del parasitoide. Se utilizaron huevos de menos de 5 horas de edad y se colocaron a temperaturas constantes de 10, 15, 20, 25, 30, y 35°C (± 1°C, 70 ± 10% HR, y 12:12 L:O h), se observó su desarrollo hasta la emergencia de adultos. El ciclo de vida del parasitoide requirió de 243.9 GDD, un umbral de temperatura inferior (UTI) de 4.8° y a 35°C no se completó el ciclo de vida siendo este el umbral de temperatura superior (UTS).

Efectos de Phytoseiulus persimilis (Athias-Henriot)1 Sobre Tablas de Vida de Tetranychus urticae Koch en Cuatro Variedades de Rosal

Resumen. Se estudió la supervivencia y esperanza de vida de Tetranychus urticae y Phytoseiulus persimilis, en cuatro variedades de rosal bajo condiciones de invernadero. Se observaron diferencias en el número de hembras de T. urticae por variedad. La curva de supervivencia de la población de T. urticae sobre las variedades Royal y Red Baiser fue de tipo I y sobre las variedades Selena y Anastasia coincide de tipo II, y entre estas curvas se encontraron diferencias significativas, dependiendo de la variedad de rosal la esperanza media de vida de T. urticae fue diferente, así como para P. persimilis. Phytoseiulus persimilis fue más eficiente sobre las variedades Selena y Anastasia, reduciendo la población de hembras adultas de T. urticae en 7 semanas.