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Fire blight, one of the most severe diseases on apples is caused by Erwinia amylovora (Ea), it provokes the death of flower buds and sometimes the whole tree. Antibiotic use is one of the methods employed to manage Ea, however, inappropriate use can lead to bacteria resistance. During 2005 and 2006, oregano (Lippia berlandieri) essential oil (80% carvacrol) was evaluated as an organic alternative to manage Ea. In vitro bactericidal minimum concentration (BMC) was 0.055 to 0.073% (w/v). A concentration of 0.11% was assessed in field and its effect on reducing the damage caused by Ea was determined. MR Results were compared against Agry-Mycin 100 , MR MR Cuprimicin 100 and Agry-Gent Plus 800 . During both years, treatments were not statistically different with respect to the control. Time of field applications was determined by detection of Ea epiphytic populations grown in semiselective media, temperature and humidity, with values of 5%, 16.7°C and 78% respectively for 2005, and 96%, 15.2 y 70% for 2006. Identification of Ea and its resistance to streptomycin was performed by growing the bacteria in semi-selective media and results were confirmed by PCR. An Ea strain resistant to streptomycin was detected and isolated. This is the first report of an Ea strain resistant to streptomycin and confirmed by molecular techniques in the most important apple area in the state of Chihuahua, Mexico. [ABSTRACT FROM AUTHOR]

Functional response of third-instar larvae of green lacewing, Chrysoperla carnea (Stephen) (Neuroptera: Chrysopidae), to four densities of single-instar larvae of the five instars of obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), was evaluated at 25 ± 1°C in a laboratory. The aims were to determine the type and other characteristics of functional response including predatory capacity of green lacewing for possible use in augmentative biological control in apple ( Malus × domestica Borkh; Rosales: Rosaceae) orchards where obliquebanded leafroller was recently introduced in Mexico. Abundance of the pest increased rapidly, causing significant foliar damage and some fruit blemish. Third-instar green lacewing larvae based on logistic regression analysis showed Type II functional response to four densities of single-instar larvae of obliquebanded leafroller. Among the five instars of prey, the largest average number consumed per green lacewing predator was a relative density of four second-instar larvae at a rate of 1.93 in 24 hours. Also, substantial average consumption was by two third-instar prey larvae per predator whereby an average of 1.5 third-instar obliquebanded leafrollers were consumed per third-instar green lacewing in 24 hours. The third-instar predator captured and consumed third-instar prey larvae in the shortest handling time ( h), i.e., only 6.46 minutes, whereas the handling times for the other instars ranged from 23.48 minutes for the fifth instar to 31.56 minutes for the fourth instar. However, attack coefficients ( a) of green lacewings were slightly greater for third- and fourth-instar prey larvae, with 0.19 hour (11.4 minutes) and 0.15 hour (9.0 minutes) until the first attack, respectively, compared to 0.09-0.11 hour (5.4-6.6 minutes) until the first attack for the other instars. Results indicated that the green lacewing could be considered a prospective candidate for use as a biological control agent against lepidopteran leafrollers. [ABSTRACT FROM AUTHOR]

Several diseases in crop plants caused by pathogenic fungi represent an economic problem due the losses they cause. Likewise, antagonistic microorganisms have been used as biological control agents such as Trichoderma spp. and Bacillus spp., among others as an efficient alternative to reduce the use of chemical fungicides in the control of crop diseases. The aim of this study was to identify the taxa of pathogens and antagonists microorganisms based on their molecular characters and to evaluate the antagonistic activity in vitro of two Bacillus isolates and two Trichoderma isolates, against five common pathogenic fungi: Fusarium oxysporum, Botrytis cinerea, Penicillium crustosum, Aspergillus nidulans, and Alternaria alternata. The nine microorganisms were used for the gDNA extraction and to amplify the 18S ribosomal DNA gene and the Internal Transcribed Spacer with the ITS primers ITS5 and ITS4 of fungi and gene of the 16S of the rDNA, using the universal primers EU(F) and EU(R) for bacteria, for molecular identification. Both T. asperellum isolates showed a significant antagonistic activity against the phytopathogenic fungi tested where the percentage of radial growth inhibition (PRGI) of the fungi colonies ranged from 43 to 71%, whereas the PRGI induced by Bacillus species, were significant, with values up to 69% when tested in vitro against B. cinerea, while the lowest effect was observed with F. oxysporum, P. crustosum, and A. nidulans. Both Bacillus species induced the presence of an inhibition halo, with values of 5 and 11 mm, when tested in vitro against F. oxysporum, and B. cinerea, respectively. The antagonistic effect of the bacterial and fungal isolates showed that these microorganisms could be used as biological control agents of several phytopathogenic fungi of crop plants. [ABSTRACT FROM AUTHOR]

The Plains lubber grasshopper, Brachystola magna Girard (Orthoptera: Romaleidae), is the main insect pest of bean, Phaseolus vulgaris L. (Fabales: Fabaceae), in Chihuahua, Durango, and Zacatecas states of México. Satisfactory control depends on diligent application of insecticide; however, given its evasive ethology and relentless arrival at bean fields, management is difficult. The use of entomopathogenic fungi has been proposed as an alternative, because they are effective and environmentally friendly. The aim of this study was to isolate and identify taxa of entomopathogenic fungi based on morphological and molecular characteristics and evaluate biological activity under laboratory conditions against B. magna adults. The Hypocreales genera of Metarhizium Sorokin and Beauveria (Balsamo) Vuillemin entomopathogenic fungi were isolated and identified based on morphological and molecular characteristics. Under laboratory conditions, the life cycles were completed in 5.6 to 8.0 days for Metarhizium spp. and 6.0 to 6.7 days for Beauveria spp. The average times to kill, were significantly different ( F = 13.3, df = 20, P < 0.0001), ranging from 3.4 to 5.7 days post-inoculation for Metarhizium isolates and 4.0 or 5.0 days for Beauveria isolates. Forty-five percent (nine) of the 20 isolates showed mycoses in ≥95% of the specimens treated with 5.5 × 107 spores ml-1 and maintained under laboratory conditions. The number of spores of both genera produced per adult grasshopper evaluated under laboratory conditions were significantly different ( F = 8.08, df = 20, P < 0.0001); Beauveria isolates produced 8 × 105 to 8.5 × 106 spores per specimen, while Metarhizium isolates produced 3.9 × 106 to 5.2 × 108 spores per specimen. Isolates of both entomopathogenic genera were applied against Plains lubber grasshopper adults in the field. Shortly after application, treated grasshoppers were collected and maintained under controlled laboratory conditions. Metarhizium isolates killed 50-100% at 9.0 days post-treatment, while Beauveria isolates killed 65-90% at a field dosage of 5.5 × 1010 spores ha-1. [ABSTRACT FROM AUTHOR]

Choristoneura rosaceana (Harris) is an emerging pest of apple Malus domestica Borkh., in Mexico. Its control depends mainly on the use of chemical insecticides; however, there are reports of natural enemies of this pest that exert a considerable control. The main objective of study was to evaluate the predatory capacity by Podisus maculiventris (Say) on C. rosaceana larvae. Twelve hundred larvae of C. rosaceana were collected in apple orchards. Moreover, 87 specimens of P. maculiventris Say of different nymphal instars were collected, of which 75 specimens were collected in apple orchards and 17 in com crops, and 22 egg groups (17 in com crops and five in apple trees). Podisus maculiventris consumption bioassays were performed over C. rosaceana larvae, where average was 0.72 larvae consumed per day, first nymphal instar showed a higher average (1.9 larvae per day) in first 24 h, and second nymphal instar showed a higher average after 7 d (1.2 larvae consumed per day). [ABSTRACT FROM AUTHOR]