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Scarabaeoidea is a diverse and widely distributed insect group; many are agricultural pests including species within the genus Phyllophaga. Species diversity studies in this taxonomic group are done mainly using morphological identification. However, despite existing taxonomic keys for adults and larvae, identification may be difficult due to their complex morphology. Molecular taxonomy can increase the value and accuracy of morphological species identification of larvae and adults. To test this, larvae collected from soil close to maize plants were identified using molecular taxonomy, and compared with adults captured using light traps. The larvae (2021) and adults (2022) were sampled on maize at the same locations in central Mexico. Molecular identification was achieved using three regions within the Cytochrome oxidase gene (cox), two in the Cytochrome c oxidase subunit 1 (cox1), Cytochrome b (CytB) and 28S rDNA. Cox gene information was more useful than nuclear information (28S). Combined morphological and molecular taxonomy of adults distinguished between seven Phyllophaga species. Although two closely related species, P. polyphyla and P. ravida , were distinguished using cox gene information, greater resolution was obtained using CytB. All analyses identified cryptic species within P. vetula. Species found amongst sampled adults were similar to those found amongst larvae. However, the number of species was greater in adults than in larvae at the same locations. Larval information showed Phyllophaga community structure changed over time. Our findings will contribute to a better understanding of Phyllophaga's ecology in maize. [ABSTRACT FROM AUTHOR]

The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is currently the most important maize pest in Mexico. Its control is mainly based on the use of conventional insecticides. Additionally, Bt-maize expressing Cry1F protein represents an alternative to control this pest. We estimated the baseline susceptibility in Mexican populations of S. frugiperda to Cry1F protein. Twenty-eight geographical populations were field collected from Baja California Sur, Chihuahua, Coahuila, Durango, Sinaloa, Sonora, and Tamaulipas states. The F 1 neonate larvae of each population were subjected to diet-overlay bioassay. After 7 d of Cry1F exposure, the percent mortality and the percent growth inhibition with respect to the untreated control were recorded (S-LAB). The LC50 ranged from 14.4 (6.3−24.0) (Cajeme 1, Sonora) to 161.8 ng/cm2 (92.0–320) (Ahumada 2, Chihuahua), while the LC95 was between 207.1 (145–363) (Obregón, Sonora) and 1,217 ng/cm2 (510.8–7,390.0) (Río Bravo 2, Tamaulipas). The sensitivity ratios at 50% mortality, (LC50 field/LC50 S-Lab) and 95% mortality were ≤6.45 and ≤5.05-fold, respectively. The 50% growth inhibition (GI50) ranged from 2.8 (0.008–9.3) (Obregón, Sonora) to 42.4 ng/cm2 (3.6–147.0) (Cajeme 1, Sonora). The GI95 was between 75.4 (San Luis Río Colorado, Sonora) to 1,198 ng/cm2 (Cajeme 1, Sonora). The relative inhibition at 50% of the growth, (RI50 = GI50 field /GI50 S-LAB) was ≤3.5 and at 95% (RI95) was ≤1.91-fold. These results indicated susceptibility to Cry1F protein in the evaluated populations of S. frugiperda. [ABSTRACT FROM AUTHOR]

BACKGROUND: The high natural resistance of the fall armyworm (FAW) to entomopathogenic fungi and the speed at which it develops resistance to chemical insecticides make it difficult to control in several crops where it is a key pest. The aim of the study was to improve mortality by combining a 50% lethal concentration of chlorpyrifos ethyl or spinosad with the entomopathogenic fungus Beauveria bassiana (Bb88) or Metarhizium anisopliae (ETL). RESULTS: Three main results were obtained. (i) Both insecticides improved the performance of the fungus when the insecticide and fungus were applied simultaneously and when spinosad preceded fungi. In control larvae treated with fungi, <1% of larvae showed fungal sporulation, but under simultaneous application of the fungus with chlorpyrifos or spinosad, 31 and 47% did so, with 68 and 93% of cadavers showing sporulation, respectively. (ii) Synergistic mortality was observed when Bb88 and spinosad were applied simultaneously, which resulted in 34% more dead larvae than the spinosad control (44%). Finally, (iii) antagonism occurred when Bb88 was applied before chlorpyrifos, when Bb88 and chlorpyrifos were applied simultaneously, and when ETL was applied before chlorpyrifos, which reduced larval mortality by 27, 31 and 19%, respectively. CONCLUSION: The synergistic mortality and improved fungal performance observed here support the hypothesis that combinations of low insecticide doses and entomopathogenic fungi can enhance integrated pest management programs and reduce the environmental impact of insecticides. Antagonism shows that some particular combinations and application sequences may produce disadvantages in pest control. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]