ABSTRACT The maize weevil (Sitophilus zeamais Motschulsky, 1855; Coleoptera, Curculionidae) is one of the most important pests associated with stored grains. It is controlled almost exclusively with synthetic insecticides. Thus, leading to problems such as pollution and resistance development. Hence an alternative is the use of natural compounds such as edible mushrooms derivates. The aim of this research was to assess, under laboratory conditions, the insecticidal and insectistatic effect of a hydroalcoholic extract of Pleurotus ostreatus (Jacq.) P. Kumm. 1871 against adults of S. zeamais. The parameters assessed were contact and fumigant toxicity, repellency, and antifeedant effect. The highest contact toxicity (57.5% mortality) was achieved with 30 mL extract L-1 solvent. No treatment showed repellent effect; the repellency index (RI) values were higher than 1, and the antifeeding activity < 30%. The fumigant effect showed a maximum of 30% mortality with the highest concentration (300 μL L-1 air). The hydroalcoholic extract of P. ostreatus exerts contact toxicity and interferes with insect reproduction or oviposition of Sitophilus zeamais.

ABSTRACT Alternative methods of control against different parasites affecting livestock and agriculture are currently being sought. The essential oil of Peumus boldus Molina has anthelmintic and insecticidal activity against the nematode Haemonchus contortus and stored cereal insect pests. The present study aimed to assess the in vitro activity of P. boldus essential oil against H. contortus (L3) unsheathed and Sitophilus zeamais, Tribolium castaneum, and Plodia interpunctella. The essential oil was obtained from leaves of P. boldus and its principal compounds identified by phytochemical analysis. Essential oil was tested at concentrations of 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0 mg mL-1 on unsheathed L3 H. contortus larvae and in concentrations of 0, 35, 70, 100, 125, 150, 175 and 200 μL L-1 air on adult insects. The main constituents detected in the essential oil were 1,8-cineole, terpineol, terpinene-4-ol, γ-terpinene, p-cimene, methyl eugenol, safrole, (E)-germacrene D, β-tujene, and ascaridol. The nematode H. contortus and insects were exposed to the essential oil for 72 h. In a bioassay with H. contortus larvae, treatment with 2.0 mg mL-1 showed the highest toxicity with 99.2% mortality. Regarding insecticidal activity, S. zeamais was the most susceptible species with a mortality of 90% at 200 μL L-1 air. The present study suggests that the essential oil of P. boldus has potential anthelmintic and insecticidal activity.

ABSTRACT Insect pests of stored cereals cause losses between 10 and 20%, which requires the search for effective and environmentally friendly control alternatives that pose no threat to human health. The objective of this study was to evaluate under laboratory conditions the insecticidal and insectistatic activity of Eucalyptus globulus and Eucalyptus nitens foliage powder against Sitophilus zeamais. The studied variables were contact and fumigant toxicity and repellent and anti-feed activity. The contact and fumigant toxicity did not exceed 40% mortality in any of the concentrations evaluated, although the concentration of 8.0% affected the progeny, recording 80.9% inhibition of adult insect emergence (F1) in E. globulus and 86.7% inhibition in E. nitens. All the treatments showed repellency and E. nitens recorded a feeding deterrence index (FDI) of 60.5%. It can be concluded that E. globulus and E.nitens powder has potential as a repellent and inhibitor of the life cycle of S. zeamais.

RESUMEN Los insectos plaga de los cereales almacenados causan pérdidas entre 10 y 20%, lo que hace necesaria la búsqueda de alternativas de control efectivas, amigables con el medio ambiente y que no representen riegos para la salud de las personas. El objetivo de la presente investigación fue evaluar, en condiciones de laboratorio, la acción insecticida e insectistática del polvo de follaje de Eucalyptus globulus y Eucalyptus nitens para el control de Sitophilus zeamais. Las variables estudiadas fueron toxicidad por contacto y fumigación y actividad repelente y anti-alimentaria. La toxicidad por contacto y fumigación no superó el 40% de mortalidad en ninguna de las concentraciones evaluadas, aunque el tratamiento de 8,0% afectó la progenie, registrando un 80,9% de inhibición de la emergencia de insectos adultos (F1) para E. globulus y de 86,7% en E. nitens. La totalidad de los tratamientos mostró efecto repelente y el polvo de E. nitens presentó un índice de disuasión de la alimentación (IDA) de 60,5%. Se concluye que el polvo de follaje de E. globulus y E.nitens presenta potencial como repelente e inhibidor del ciclo de S. zeamais.

Resumen El psílido de la papa/tomate, Bactericera cockerelli, es una de las plagas más importantes de cultivos de solanáceas en el mundo. Spirotetramat y spiromesifen son insecticidas comúnmente utilizados contra esta plaga y actúan inhibiendo la acetil CoA carboxilasa, y con ello evitan la biosíntesis de lípidos. Se evaluó el efecto de los insecticidas sobre el comportamiento de oviposición de B. cockerelli en plantas de chile habanero [Capsicum chinense (Jacq)]. El follaje de la planta se dividió en tres estratos (superior, medio e inferior) y todas las combinaciones de estratos se trataron por separado con 30 mL de la solución a una concentración de 1 mL L-1 de formulación comercial, se utilizó una torre Potter a 0.703 kg cm-2 de presión, calibrada para aplicar 2 mL cm-2. Después de 1 h de tratamiento se retiró la cubierta plástica de los estratos no tratados, y las plantas de cada tratamiento se infestaron con 20 pares de adultos de 20 a 24 h y se les permitió ovipositar durante 7 d. Se registró el número de huevos por hoja por estrato y se calculó su porcentaje. El porcentaje de huevos por hoja en el testigo en los estratos superior, medio e inferior fue 42, 32 y 26 %, respectivamente. El Spiromesifen inhibió significativamente (P ≤ 0.05) la oviposición sólo en la capa tratada. El Spirotetramat redujo significativamente (P ≤ 0.05) la tasa de oviposición, independientemente del estrato tratado, lo que indica actividad biológica en partes no tratadas de la planta, ya sea por encima o por debajo de la parte tratada.

Summary The potato/tomato psyllid, Bactericera cockerelli, is one of the most important pests of solanaceous crops in the world. Spirotetramat and spiromesifen are insecticides commonly used against this pest and act by inhibiting acetyl CoA carboxylase, thus preventing the biosynthesis of lipids. Their effect of the insecticides on the oviposition behavior of B. cockerelli on habanero pepper plants, [Capsicum chinense (Jacq)] was evaluated. The foliage of the plant was divided into three strata (upper, middle and lower), and all the strata combinations were treated separately with 30 mL of the solution at a concentration of 1 mL L-1 of commercial formulation using a Potter tower at 0.703 kg cm-2 of pressure, calibrated to apply 2 mL cm-2. After 1 h of treatment, the plastic cover was removed from the untreated strata, and the plants of each treatment were infested with 20 pairs of 20 to 24 h-old adults and allowed them to oviposit for 7 d. The number of eggs per leaf per stratum was recorded and its percentage was calculated. The percentage of eggs per leaf in the control at the upper, middle and lower strata was 42, 32 and 26 %, respectively. Spiromesifen significantly (P ≤ 0.05) inhibited oviposition only in the treated layer. Spirotetramat significantly (P ≤ 0.05) reduced the oviposition rate, regardless of the treated stratum, indicating biological activity on untreated parts of the plant, either above or below the treated part.

ABSTRACT Sitophilus zeamais is one of the major pests of stored cereals worldwide and its control is based on the use of synthetic insecticides, but their irrational use has caused environmental pollution and resistance. Essential oils have shown contact and fumigant insecticidal effect and could be an alternative to synthetic compounds. Hence, the insecticidal properties of essential oil of Chenopodium ambrosioides L. were assessed under laboratory conditions against adults of Sitophilus. zeamais. The variables studied were contact and fumigant toxicity, and antifeedant and repellent activity. Mortality by contact toxicity did not exceed 30% in all the treatments evaluated. The highest F1 reduction was observed in the treatment of 4.0% with 41.3% of emergence (58.7% of inhibition). Grain weight loss was lower than 9.0% and maize germination was not affected. All treatments exhibited fumigant activity, while concentrations equal to or lower than 0.5% showed repellent and feeding deterrent effect. It can be concluded that essential oil of Ch. ambrosioides has potential for S. zeamais control.

RESUMEN Sitophilus zeamais Motschulsky es a nivel mundial una de las principales plagas de los cereales almacenados y su control se basa en insecticidas sintéticos, pero su uso irracional ha provocado contaminación del ambiente y resistencia. Los aceites esenciales han mostrado efecto insecticida de contacto y fumigante por lo que podrían constituir una alternativa a los compuestos sintéticos. Por este motivo se evaluaron, en condiciones de laboratorio, las propiedades insecticidas del aceite esencial de Chenopodium ambrosioides L. contra adultos de S. zeamais. Las variables evaluadas fueron toxicidad por contacto y fumigación, y actividad antialimentaria y repelente. La mortalidad por contacto no superó el 30% en todos los tratamientos evaluados. La mayor reducción de la F1 se observó en el tratamiento de 4,0% con 41,3% de emergencia (58,7% de inhibición). La pérdida de peso de los granos fue menor a 9,0% y la germinación del maíz no se vio afectada. Todos los tratamientos mostraron actividad fumigante y las concentraciones iguales o superiores a 0,5% tuvieron efecto repelente y antialimentario. Se concluye que el aceite esencial de Ch. ambrosioides presenta potencial para el control de S. zeamais.

ABSTRACT The maize weevil, Sitophilus zeamais Motschulsky, is one of the most important pests of stored cereals worldwide. Currently, it is mainly controlled with the use of synthetic insecticides, with poor variation of action mechanisms. Natural compounds, particularly plant extracts, are an alternative to control this pest. The objective of this study was to evaluate, under laboratory conditions, the insecticidal/insectistatic effect of extracts with different polarity solvents of Pleurotus ostreatus Kumm against S. zeamais adult. The variables evaluated were contact and fumigant toxicity, repellency and antixenosis. A completely randomized experimental design was used. The highest toxicity was obtained by fumigation with ethyl acetate extract with a mortality of 100% at a concentration of 30 µL 0.15 L-1 air, and a CL50 of 18,3 µL at 0,15 L-1 air. Extracts in ethyl acetate and distilled water showed repellent activity, while all extracts exhibited antixenosis effects. It can be concluded that P. ostreatus extract in ethyl acetate has fumigant, repellent and antixenotic activity against S. zeamais adult.

RESUMEN El gorgojo del maíz, Sitophilus zeamais Motschulsky, es a nivel mundial una de las plagas más importantes de los cereales almacenados. Actualmente su manejo se realiza principalmente con insecticidas sintéticos, con escasa variación de mecanismos de acción, por lo que una alternativa son los compuestos naturales, especialmente los extractos vegetales. El objetivo de esta investigación fue evaluar, en condiciones de laboratorio, el efecto insecticida/insectistático de extractos de Pleurotus ostreatus Kumm con solventes de distinta polaridad para el control de adultos de S. zeamais. Las variables evaluadas fueron toxicidad por contacto y fumigación, repelencia y antixenosis, con un diseño experimental completamente al azar. La mayor toxicidad se obtuvo por fumigación con el extracto en acetato de etilo con una mortalidad de 100% en la concentración 30 µL en 0,15 L-1 aire y una CL50 de 18,3 µL en 0,15 L-1 aire. Los extractos en acetato de etilo y agua destilada mostraron actividad repelente y todos registraron efecto de antixenosis. Se concluyó que el extracto de P. ostreatus en acetato de etilo presenta actividad fumigante, repelente y antixenótica sobre adultos de S. zeamais.

ABSTRACT Extracts rich in saponins from Quillaja saponaria Mol. and populations of rhizobacteria from the genus Pseudomonas, which produce antimicrobial compounds, have been associated with reduction of the fungus Gaeumannomyces graminis var. tritici, the causal agent of take-all disease, which is responsible for severe loss of wheat (Triticum aestivum L.) crops worldwide. However, there is a limited background on the interaction between these bacteria and natural triterpenoids. The aim of this research was to assess the effect of saponin rich extract on Pseudomonas protegens strains 2,4-diacetylphloroglucinol-producers under in vitro and in plant conditions and determining the synergistic effect to be used together to control G. graminis var. tritici in wheat plants. We determined that 8% and 90% of saponins rich Q. saponaria extracts have a differential effect on P. protegens according to their purity (P ( 0.05). On wheat seedlings, quillaja extract with 90% of saponins did not affect the three antagonistic bacterial strain populations assessed, but affected biofilm formation at saponins concentration of 7360 mg L-1. Pseudomonas protegens strains had a variable antagonist activity in wheat plants, and controlled the fungus when were combined with different concentrations of pure Q. saponaria extract, with the concentration of 1840 ppm reducing the take-all disease in 32.5% with respect to the control inoculated with G. graminis var. tritici (P ( 0.05). However, no synergistic effects when the plant extract was combined with the bacterial strains were observed. These results showed the promising and complexity of combining bacterial and plant extract to develop a biopesticide, which could control this fungal disease.

Synthetic pesticides are the most widely used method to control insect pests. However, today we have insecticide resistance reports and mammal intoxications. The essential oil of Eucalyptus species has shown promising results in the control of several insect pests. The objective of this research was to assess the chemical composition, toxicity and repellent effect under laboratory conditions of essential oil of Eucalyptus globulus and Eucalyptus nitens against adults of Sitophilus zeamais. The phytochemical analysis indicates that the major constituents of both essential oils are 1.8-cineol (eucalyptol) (55.49% in E. globulus and 59.85% in E. nitens) and a-pinene (18.18% in E. globulus and 18.36% in E. nitens). The oils of both species showed no significant contact toxicity although they affected the F1 emergence of S. zeamais, which was reduced in more than 50% with E. globulus in concentrations of 4 and 8% without affecting seed germination. Fumigant toxicity values of mortality higher than 70% were obtained with E. nitens in treatments of 20, 25, 30 and 35 and in E. globulus with 35 ^L. All treatments were repellents to S. zeamais. We conclude that essential oils of E. globulus and E. nitens have significant insecticidal fumigant properties against S. zeamais.

Los insecticidas sintéticos son el método más utilizado para el control de insectos plaga, sin embargo actualmente se ha reportado desarrollo de resistencia y toxicidad para mamíferos. El aceite esencial de especies del género Eucalyptus ha mostrado resultados promisorios en el control de diversos insectos. El objetivo de esta investigación fue evaluar, en laboratorio, la composición química, toxicidad y efecto repelente del aceite esencial de Eucalyptus globulus y Eucalyptus nitens para el control de adultos de Sitophilus zeamais. Los análisis fitoquímicos indicaron que los mayores constituyentes del aceite esencial de ambas especies son 1,8-cineol (eucaliptol) (55,49% en E. globulus y 59,85% en E. nitens) y a-pineno (18,18% en E. globulus y 18,36% en E. nitens). Los aceites de ambas especies no presentaron toxicidad significativa por contacto aunque afectaron la emergencia de la F1 de S. zeamais la cual se redujo en más de un 50% con E. globulus en concentraciones de 4 y 8% sin afectar la germinación de las semillas. En la toxicidad como fumigante se obtuvieron valores de mortalidad superiores al 70% en los tratamientos de 20, 25, 30, 35 con E. nitens y con 35 en E. globulus. Todos los tratamientos fueron repelentes contra S. zeamais. Se concluyó que los aceites esenciales de E. globulus y E. nitens presentan propiedades insecticidas significativas como fumigante y repelente para el control de adultos de S. zeamais.

The maize weevil (Sitophilus zeamais Motschulsky) is one of most important pest of stored seeds worldwide, but its current control method is based on the use of synthetic insecticides, usually leading to undesirable problems such as insecticide residues on treated food, human intoxications, and insect resistance development. Therefore the search of friendly alternative methods is required. The aim of this study was to assess, under laboratory conditions, the insecticidal properties of Peumus boldus Molina, Laurelia sempervirens (Ruiz & Pav.) Tul., and Laureliopsis philippiana (Looser) Schodde essential oils against S. zeamais. The phytochemical analysis of the three essential oils showed 1,8-cineole, safrole and methyleugenol as the common components; all of them documented with insecticidal activity from essential oils from other plant species. The highest toxicity (100% mortality) of these three oils acting as a contact insecticide was observed at 24 h exposure at 4% concentration. The estimated LC50 values for P. boldus, L. sempervirens, and L. philippiana were 0.37, 1.02, and 0.28 μL g-1, respectively. Peumus boldus exhibited the highest fumigant activity with 100% adult mortality at 30 μL oil L-1 air. At ≥ 0.5% (v/w) concentration, all essential oils showed repellent activity. These three essential oils showed a promissory insecticidal activity against the maize weevil.

In the State of Mexico, cut rose (Rosa x hybrida) grown under greenhouse conditions has as a commercial constraint the low phytosanitary quality of its flower buds. To improve this quality, three growth regulators containing cytokinins (two commercial products and one prepared at a dose of 0.001 ppm from a technical-grade growth regulator, all at three frequencies of application) and CP* Floral Protector (FP) were evaluated in cut Rosa x hybrid 'Polo' grown under greenhouse conditions in Villa Guerrero, State of Mexico. A completely randomized experimental design with 20 treatments and four replications in a factorial arrangement was used. Treatments were applied to flower buds of 0.5 cm in diameter with closed sepals. Evaluations were made according to commercial harvest criteria when the petals begin to separate from the center of the flower. The FP and application of growth regulators increased bud diameter and length (P ≤ 0.05), but there was no effect on peduncle length or the number of days to harvest. FP use prevented insect damage and increased the number of export-quality buds. CP® floral protector and growth regulators improve the quality of cut roses.

En el Estado de México, la rosa de corte (Rosa x hybrida) que se produce en invernadero tiene como limitante comercial la baja calidad fitosanitaria de los botones florales. Para incrementar dicha calidad, se evaluaron en Villa Guerrero, Estado de México tres reguladores del crecimiento que contienen citocininas (dos comerciales y uno preparado a la dosis de 0.001 ppm a partir del regulador de crecimiento grado técnico; todas con tres frecuencias de aplicación) y el Protector Floral CP* (PF) en Rosa x hybrida 'Polo' de corte en invernadero. Se utilizó un diseño experimental completamente al azar con 20 tratamientos y cuatro repeticiones en arreglo factorial. Los tratamientos se aplicaron a botones florales de 0.5 cm de diámetro con los sépalos cerrados. Las evaluaciones se hicieron de acuerdo al criterio comercial de punto de corte cuando los pétalos empezaban a separarse del centro de la flor. El PF y la aplicación de reguladores del crecimiento incrementaron el diámetro y longitud del botón (P ≤ 0.05), pero no hubo efecto en la longitud del pedúnculo ni en los días al corte. El uso del PF previno daños por insectos e incrementó el número de botones con calidad de exportación. El protector floral CP* y los reguladores del crecimiento mejoran la calidad de la rosa de corte.

The control of black Sigatoka (Mycosphaerella fijiensis) of banana (Musa acuminate Colla AAA) and (Musa balbisiana Colla AAB) requires numerous applications of fungicides, mainly of the triazoles group that impose high selection pressure in populations of this pathogen. The aim of the this study was to determine the response of strains of Mycosphaerella fijiensis isolated from banana plantations of Tabasco and Chiapas, México, to propiconazol and tridemorph. The bioassays were carried out in potato dextrose agar (PDA®) culture medium added with different concentrations of these fungicides. The media were inoculated with 100 µL of a conidial suspension and mycelia fragments of the fungus, and incubated in darkness at 26 °C for 7 d. The effective concentration 50 (EC50) and 95 % (EC95) was estimated through Probit analysis of the percentage of inhibition of the relative growth of the pathogen. The EC50 values in propiconazol varied from 0.0001 to 0.95 mg L-1 and those of EC95 from 0.006 to 12.51 mg L-1. The resistance ratio at the level of EC95 was higher than 2085x, for the isolate MF-RmC2 of the Remedios plantation from Teapa, Tabasco. The values for EC50 in tridemorph varied from 0.00001 to 0.002 mg L-1 and those of EC95 from 0.03 to 0.85 mg L-1. The resistance ratio to level EC95 between the sensitive isolate of reference and the least susceptible (MF-RcC5 of the Recreo plantation, Tabasco) was higher than 28.3x. The positive correlation between the number of applications and the values of EC50 and of EC95 are indicative that the selection pressure exerted in this plantation generated resistance to the propiconazol.

El control de Sigatoka negra (Mycosphaerella fijiensis Morelet) del banano (Musa acuminata Colla AAA) y plátano (Musa balbisiana Colla AAB) requiere de numerosas aplicaciones de fungicidas, principalmente de los grupos triazoles que inducen alta presión de selección en poblaciones del patógeno. El objetivo del presente estudio fue determinar la respuesta de cepas de M. fijiensis aisladas de plantaciones de banano de Tabasco y Chiapas, México, al propiconazol y tridemorf. Los bioensayos se realizaron en medio de cultivo Papa Dextrosa Agar (PDA®) adicionados con diferentes concentraciones del fungicida. Los medios se inocularon con 100 µL de una suspensión conidial y fragmentos miceliares del hongo, y se incubaron en oscuridad a 26 °C por 7 d. La concentración efectiva 50 (CE50) y 95 % (CE95) para cada aislamiento se estimó mediante análisis Probit del porcentaje de inhibición del crecimiento relativo del patógeno. Los valores CE50 en propiconazol variaron de 0.0001 a 0.95 mg L-1; y los de CE95 de 0.006 a 12.51 mg L-1. La proporción de resistencia en el nivel CE95 fue superior a 2085x, para el aislamiento MF-RmC2 de la finca Remedios en Teapa, Tabasco. Los valores para CE50 en tridemorf variaron de 0.00001 a 0.002 mg L-1 y los de CE95 de 0.03 a 0.85 mg L-1. La proporción de resistencia a nivel CE95 entre el aislamiento sensible de referencia y el menos susceptible (MF-RcC5 de la finca el Recreo, Tabasco) fue superior a 28.3x. La correlación positiva entre el número de aplicaciones y los valores de CE50 y de CE95 son indicativos de que la presión de selección ejercida en esta plantación generó resistencia al propiconazol.

Gynaikothrips ficorum (Marchal) is a pest of the laurel tree in urban zones and insecticides are possibly used for its control, but its initial response to these products is unknown. Therefore susceptibility of various populations of this species was determined (Texcoco, Córdoba and Tlayacapan) to the insecticides permethrin, cypermethrin, diazinón, malathion, methyl oxydemeton, methyl parathion, endosulfán and methomyl. The Texcoco population was used as reference to make comparisons of the response. At 24 h of exposure, the confidence levels of the CL50 of the three populations overlapped in the insecticides cypermethrin, diazinón, malathion and methyl oxydemeton; but they did not overlap in Córdoba and Tlayacapan with Texcoco, for permethrin, methyl parathion, endosulfán and methomyl. For Córdoba and Tlayacapan with cypermethrin, the resistance proportion (RP50) was 0.88 and 0.53'; with diazinón, 0.3 and 0.29'; with malathion 1.04 and 1.02'; with methyl oxydemoton 0.74 and 7.18'; with methyl parathion 8.4 and 4.63'; with endosulfán 1.19 and 0.2', and with methomyl 0.11 and 0.53'. At 95 % mortality, only in Tlayacapan and for endosulfán (RP95=0.03), the fiducial limits did not overlap with the other two populations. The values obtained at 48 h of exposure followed the same tendencies found at 24 h. These response values correspond to a susceptible state and can be used as comparison reference.

Gynaikothrips ficorum (Marchal) es una plaga del laurel en zonas urbanas y posiblemente se usan insecticidas para su control, pero se desconoce su respuesta inicial a éstos. Por tanto, se determinó la susceptibilidad de varias poblaciones de esta especie (Texcoco, Córdoba y Tlayacapan) a los insecticidas permetrina, cipermetrina, diazinón, malatión, oxidemetón metílico, paratión metílico, endosulfán y metomil. La población Texcoco se usó como referencia para hacer comparaciones de la respuesta. A las 24 h de exposición, los límites de confianza de la CL50 de las tres poblaciones se traslaparon en los insecticidas cipermetrina, diazinón, malatión y oxidemetón metílico; pero no se traslaparon en Córdoba y Tlayacapan con Texcoco, para permetrina, paratión metílico, endosulfán y metomil. Para Córdoba y Tlayacapan con cipermetrina, la proporción de resistencia (PR50) fue 0.88 y 0.53'; con diazinón 0.3 y 0.29'; con malatión 1.04 y 1.02'; con oxidemetón metílico 0.74 y 0.9'; con permetrina 5 y 7.18'; con paratión metílico 8.4 y 4.63'; con endosulfán 1.19 y 0.2', y con metomil 0.11 y 0.53'. A nivel del 95 % de mortalidad, sólo en Tlayacapan y para endosulfán (PR95 =0.03), los límites fiduciales no se traslaparon con las otras dos poblaciones. Los valores obtenidos a las 48 h de exposición siguieron las mismas tendencias encontradas a las 24 h. Estos valores de respuesta corresponden a un estado susceptible y se podrán usar como referencia de comparación.

Spiromesifen is an insecticide that inhibits the synthesis of lipids and, in Mexico, its use against the Tomato-Potato Psyllid, Bactericera cockerelli (Sulc), on chili pepper (Capsicum annum), tomato (Lycopersicon sculentum) and potato (Solanum tuberosum) began in 2005; however more information is needed to understand its toxicity on this insect pest. The aim of this research was to determine the toxicity of spiromesifen against each of the biological stages of tomato-potato psyllid, its effect on fertility and viability of eggs deposited by treated females, as well as the female preference to lay eggs on treated and non treated plants. The relative toxicity at 95% mortality (highest LC95 value /LC95 value of the respective biological stage) of spiromesifen in egg, nymph 1, nymph 2, nymph 3, nymph 4, and nymph 5 were 517.5; 31316.2; 2950.1; 315.6; 18.2 and 1-fold, respectively. There were no differences in the toxicity of spiromesifen between adult males and females. The number of laid eggs was reduced as the spiromesifen concentration used to treat female increased and egg hatch was reduced in all tested doses. In the "no choice" test, females deposited 38.6 ± 2.01 eggs by leaf of non treated chili pepper type jalapeño, while in the treated with 360 mg L-1 we observed 0.3 ± 0.08 eggs by leaf. In the "choice" test, the oviposition decreased as the dose increased. There were no eggs on plants treated with 2400 mg L-1 of spiromesifen.

In two field-collected populations of de Bemisia tabaci (Gennadius) B biotype previously selected with the neonicotinoid insecticide thiamethoxam (NEO-R, NEO-N), and a population susceptible to insecticides (SUSC), the level of response to the insecticide thiametoxam, as well as the life and fertility tables were determined. At LC95, the NEO-R population showed a resistance ratio (RR95) value of 8.8-fold, an intrinsic rate of increase (r m) of 0.72. The fitness of the NEO-R and NEO-N populations in relation to the SUSC was 1.5 and 2.0, respectively. The RR95 value for NEO-N was 1.9-fold; it's r m value was 0.082, while in the SUSC population was 0.041. The developmental time of egg and adult were longer in NEO-R population, while the nymph and pupa lasted longer in the NEO-N and SUSC populations. The developmental time was different in the three NEO-R, NEO-N, and SUSC populations with 19.7 d (315.84 degree days or dd), 15.7 d (250.4 dd) and 18.5 d (296.6 d), respectively. The populations previously selected with thiamethoxam did not reproduce faster than their susceptible counterpart.

The insecticidal properties of boldus (Peumus boldus Molina) powder used alone and mixed with lime against adults of maize weevil (Sitophilus zeamais Motschulsky) were evaluated under laboratory conditions. Additionally, aeration effects (presence or absence) and temperature (room temperature vs. 3 °C) on insecticidal properties were studied over time. A mortality rate of 100% was observed at 20 g kg-1 (w/w) of P. boldus powder when used alone and mixed with lime in proportions of 50:50, 60:40, and 80:20. The 50% lethal concentration (LC50) for all treatments was < 5 g kg-1, while LC90 was 11 g kg-1. Mixing corn grains with different insecticidal treatments did not affect maize germination. Temperature and aeration did not influence mortality of maize weevil adults. When the boldus powder was mixed with the infested maize 24 h before grinding, the toxicity to the parental adults and emergence of F1 adults with respect to the untreated control was 100 and 0%, respectively. The results were not satisfactory when boldus powder was stored during 30, 60, and 90 d and then mixed with the infested maize. Boldus foliage toxicity was high 24 h after grinding, but decreased significantly over time.

Se evaluaron las propiedades insecticidas del polvo de boldo (Peumus boldus Molina), solo y en mezcla con cal, bajo condiciones de laboratorio. Adicionalmente, se evaluó el efecto de la aeración (presencia vs. ausencia) y de la temperatura (temperatura ambiente vs. 3 °C ) sobre la mortalidad y emergencia de adultos de la F1. La concentración de 20 g kg-1 (p/p) del polvo de boldo ya sea solo o en combinación con cal en las proporciones de 50:50, 60:40 y 80:20 mostraron 100% de mortalidad. La concentración letal 50% (CL50), en todos los tratamientos fue menor a 5 g kg-1 (p/p) mientras que la CL90 no superó 11 g kg-1 (p/p). La mezcla del polvo con los granos de maíz tanto solo como en mezcla con cal no afectó la germinación. La temperatura y la aeración no afectaron la mortalidad de los adultos parentales ni la emergencia de adultos de la F1. Cuando se mezcló el maíz con el polvo de boldo molido 24 h antes de la infestación con adultos, la mortalidad de los adultos parentales y la emergencia de adultos de la F1 fue de 100 y de 0%, respectivamente. Los resultados no fueron satisfactorios cuando el polvo de boldo almacenado durante 30, 60 y 90 d fue mezclado con el maíz infestado. La toxicidad del follaje de boldo es alta 24 h después de pulverizarse; si el tiempo es mayor, la toxicidad declina significativamente.