Gabriel Gallegos-Morales

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).

Mortality and Production of Occlusion Bodies in Spodoptera Frugiperda Larvae (Lepidoptera: Noctuidae) Treated with Nucleopolyhedrovirus

ABSTRACT The fall armyworm (FAW), Spodoptera frugiperda is the main corn pest in Latin America. As an alternative to chemical insecticide applications, one isolate of Spodoptera frugiperda nucleopolyhedrovirus from soil of an experimental field in Saltillo, Coahuila, Mexico was evaluated. Egg masses of the pest were superficially inoculated by the immersion method, with different nucleopolyhedrovirus concentrations expressed as occlusion bodies/mL (OBs/mL). Artificial diet was also inoculated with different viral concentrations and used to conduct bioassays on first to sixth instar larvae to determine the number of OBs produced per larva. Another assay was performed under greenhouse conditions to evaluate four baculovirus formulations. The use of the immersion method on egg masses caused the highest mortality rates recorded in the larval stage (74.37%), mainly in the first instar, with 64.05% mortality. The number of OBs produced per larva ranged from 5.15 × 106 to 2.3 × 109, where fifth and sixth instar larvae produced the highest amount. OBs produced by weight unit of larva were registered and higher values were found in the last larval instars. In the baculovirus formulations tested under greenhouse conditions, the mixture with maize flour and starch resulted in significantly increased mortality rates.

Note:In vitro antagonism of actinomycetes isolated from fungus-growing ants against plant pathogenic fungi

Fungus-growing ants have been found recently to be symbiotic with actinomycetes living on the ant’s cuticle; these bacteria are inhibitory to soil fungi that are detrimental to the ants’ fungus gardens. In order to investigate whether actinomycetes found on the cuticle of attine ants also had inhibitory properties against plant pathogenic fungi, we isolated 32 strains of actinomycetes from fungus-growing ants (Atta, Trachymyrmex, andCyphomyrmex), from the Mexican states of Coahuila, Nuevo León and Tamaulipas. Of the actinomycetes tested against selected plant pathogenic fungi (Alternaria solani, Aspergillus flavus, Colletotrichum lindemuthianum, Rhizoctonia solani, Sclerotium sp.) on Czapek-Dox agar medium, 13 isolates inhibited at least one of the fungi.C. lindemuthianum was inhibited by 11 actinomycetes, andRhizoctonia by three. An actinomycete strain isolated fromCyphomyrmex rimosus inhibited all five fungi tested.

Biological Activity of Hyphomycete Entomopathogenic Fungi Against Gynaikothrips uzeli (Thysanoptera: Phlaeothripidae)

Weeping fig, Ficus benjamina L. (Moraceae) is an ornamental plant species grown worldwide. In Mexico, it is one of the most widely used ornamentals in urban green areas. Leaves of the tree are damaged by the thrips Gynaikothrips uzeli Zimmerman (Cambero et al. 2010). Thrips feed on leaf terminals and inject toxins causing deformed leaves and gall formation (Held et al. 2005; Retana-Salazar & Sanchez-Chacon 2009). Chemical control of Gynaikothrips spp. is possible (Held & Boyd 2008), but insecticides should be used wisely in order to preserve associated natural enemies (Wheeler et al. 2007). In Mexico, Montandoniola confusa Streito & Matocq and Androthrips ramachandrai (Karny) have been found to be predators of Gynaikothrips spp (Cambero et al. 2010). In North America north of Mexico, A. ramachandrai, Montandoniola moraguesi Puton and Thripastichus gentilei (Del Guercio) are reported natural enemies (Held et al. 2005; Held & Boyd 2008).

First Records of Lespesia postica and Vibrissina mexicana (Tachinidae) as Parasitoids of Monoctenus sanchezi (Diprionidae)

Abstract. Parasitoid flies of white cedar sawfly, Monoctenus sanchezi Smith, were identified molecularly and morphologically. Third and fourth instars of sawfly larvae were collected in white cedar trees, Juniperus flaccida Schltdl, at Sierra de Alvarez, San Luis Potosi, in 2011, 2012, and 2013. The material collected was taken to Universidad Autonoma Agraria Antonio Narro and identified to family. Molecular characterization was done at CINVESTAV Campus Irapuato, and DNA sequences were compared with GenBank Blast. Parasitoids obtained were Vibrissina mexicana (Aldrich) and Lespesia postica (Walker) (Diptera: Tachinidae) with 99 and 97% similarity, respectively. Parasitism of white cedar sawfly was 2.6, 4.25, and 5.5% in 2011, 2012, and 2013, respectively.

Characterization of baculovirus isolates obtained from soil by restriction fragment patterns

Actually, a diversity of baculovirus has been demon-strated by the characterization of different geographic isolates, especially with the genotypic variants present within the same isolate. Knowledge of the natural diversity, inter- and intra-specific, could contribute to a better classification of baculovirus, as well as being of special importance for the design of bio-insecticides, whose genetic material could be included in the improve-ment of strains with better potential for application in specific agroecosystems (Munoz et al., 2001). Baculoviruses are classified according to the host from which was isolated, although they are highly specific, there are baculovirus infecting several host species, making reference to them by different names

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.

Propagation and Evaluation in vivo of Granulosis Virus of Phthorimaea operculella (Zeller)1

Abstract. Four methods for propagation of Granulovirus phthorimaea on Phthorimaea operculella (Zeller) larvae were evaluated under laboratory conditions. The methods were: immersion of potato, Solanum tuberosum L., tuber; application by cotton swab to larvae; larval immersion and aspersion with viral suspension (homogenized water with one to 15 infected larvae). The objectives were to develop a method adapted to in vivo production of the virus and to determine susceptibility of P. operculella to the virus. Larval immersion was significant at 5, 10, and 15 days after evaluation, killing 55.0, 77.5, and 87.5%, respectively, of second and third instars. LC50 was estimated based on the number of first-instar larvae per liter of water (0, 1, 3, 6, 9, 12, and 15). LCs were 7.8, 3.7, and 2.0 larvae per liter of water at 2, 5, and 8 days, respectively, and varied according to the time data were collected.

Protección de Frutos de Manzano con el Virus de la Granulosis de Cydia pomonella L. (Lepidoptera: Tortricidae)

Los baculovirus son patógenos específicos de invertebrados que se emplean como bioinsecticidas de insectos plaga, particularmente de especies del orden Lepidoptera (Black et al. 1997). El granulovirus de (CpGV) fue aislado de huertas de manzana en México (Tanada 1964), causa virulencia, mostrando una DL50 de 1 a 5 cuerpos de inclusión (COs) para larvas del primer estadio (Allaway y Paine 1984, Huber 1986). Esta alta patogenicidad se refleja en la muerte de la larva infectada, principalmente debido a su capacidad poliorganotrópica (Ibarra y Del Rincón 2001). Después de la ingestión de CpGV por la larva, el gránulo se disuelve en el intestino medio alcalino y se liberan los viriones que inician la infección en las células epiteliales, donde se replica y se extiende a través de los tejidos del insecto, conduciéndolo a la muerte (Federici 1997, Thiem 1997). En el manzano el potencial del virus CpGV como agente de control biológico se debe a su alta especificidad (Crook 1991). Además su eficiencia en campo, permite compararlo con insecticidas químicos en su capacidad para controlar el daño de la palomilla de la manzana (PM) (Charmillot et al. 1991, Stará y Kocourek 2003). Se evaluó el efecto de concentraciones menores a las comercialmente recomendadas del virus CpGV para el control de larvas de , debido su alto potencial para ser utilizado como insecticida biológico, con la posibilidad de reducir los costos de aplicación usando dosis más bajas pero efectivas en el control de esta plaga. El trabajo experimental se realizó en el año 2006 en un huerto de manzano con variedades Golden y Red Delicious de 10 ± 2 años de edad, localizado en Jamé, Municipio de Arteaga, Coahuila (25° 21 ́ 59 ́ ́ latitud norte y 100° 37 ́ 11 ́ ́ longitud oeste y 2280 msnm). Las temperaturas máximas y mínimas diarias del 1o de abril al 29 de julio de 2006, se obtuvieron de la estación meteorológica de la Comisión Nacional del Agua, localizada a 100 m del sitio experimental. Para la aplicación del granulovirus contra la primera generación de la PM se utilizó un diseño de bloques al azar con 12 tratamientos. Cada tratamiento constó de cinco repeticiones. Cada árbol de manzano constituyó una unidad experimental. Las aplicaciones de CpGV se realizaron con base al producto Granupom (PROBIS GmbH, I m Kazenloch, Wiernsheim, Alemania). Se utilizó una aspersora