Effects of glyphosate on the non-target leaf beetle Cerotoma arcuata (Coleoptera: Chrysomelidae) in field and laboratory conditions

This study aimed to assess the glyphosate application effects on the Cerotoma arcuata Oliver (Coleoptera: Chrysomelidae) population in glyphosate-resistant soybean crops. Field studies were conducted with glyphosate and the insecticide endosulfan to observe the effects of these pesticides on C. arcuata, on its damages in the crop and on the populations of natural enemies in glyphosate-resistant soybean crops. Moreover, the lethal and behavioral sublethal response of C. arcuata to glyphosate and endosulfan was conducted in the laboratory. The results of the field and laboratory experiments showed that glyphosate caused moderate toxicity and high irritability in C. arcuata and that endosulfan caused high toxicity and irritability. Therefore, the direct effect of glyphosate on C. arcuata was negative and does not explain the population increases of this pest in glyphosate-resistant soybean. However, the glyphosate also decreased the density of predators. Thus, the negative effect of glyphosate on the predators may be related to population increases of C. arcuata in glyphosate-resistant soybean crops, however, more studies are needed to better evidence this relationship. This study suggests that glyphosate can impact other non-target organisms, such as herbivorous insects and natural enemies and that the use of this herbicide will need to be carefully stewarded to prevent potential disturbances in beneficial insect communities in agricultural systems.

Wax Removal and Diamondback Moth Performance in Collards Cultivars

The diamondback moth Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae) is an herbivorous specialist on Brassicaceae species. Brassicas spp. plants developed a range of defenses (chemical, physical, and morphological) to prevent herbivores attack. In this study, we reported the antixenotic and antibiotic effects of outermost layer of two species of epicuticular wax of Brassicaceae, Brassica oleracea L. var. "Santo Antônio," and Hybrid Kope F1 100MX, on larvae and adult of P. xylostella. In the choice experiment, P. xylostella adults showed an oviposition preference for collard cultivars Santo Antônio (control) and Hybrid Kope F1 100MX with wax removal. In the no-choice experiment, oviposition was 6.4 times higher in the Hybrid Kope F1 100MX with wax removal than without wax removal. There were significant differences among larvae feeding on leaf disks of Hybrid Kope F1 100MX in the treatments with (65.3 mg) and without wax removal (23.5 mg). The net reproduction rate (R ₀ ), and intrinsic (rm) and finite rates of increase (λ) of P. xylostella in the cv. Santo Antônio were bigger in the treatment without wax removal (R ₀  = 50.4, rm = 0.23 and λ = 1.26) than treatment with wax removal (R ₀  = 28.5, rm = 0.20 and λ = 1.22). However, only the R ₀ value was affected by mechanical wax removal in the Hybrid Kope F1 100MX (with wax removal R ₀  = 43.3 and without wax removal R ₀  = 30.8). In conclusion, the results indicate that collard's wax is important to accessibility and development of P. xylostella, and its removal changes the resistance of collard's varieties to P. xylostella.

Polymorphic microsatellite markers for the rare and endangered cactus Uebelmannia pectinifera (Cactaceae) and its congeneric species

The cactus genus Uebelmannia includes 3 narrow endemic species associated with rocky savanna habitats in eastern South America. Because of their rarity and illegal over-collection, all of these species are endangered. Taxonomic uncertainties resulting from dramatic local variation in morphology within Uebelmannia species preclude effective conservation efforts, such as the reintroduction or translocation of plants, to restore declining populations. In this study, we developed and characterized 18 perfect, dinucleotide simple-sequence repeat markers for U. pectinifera, the most widely distributed species in the genus, and tested the cross-amplification of these markers in the remaining congeneric species and subspecies. All markers were polymorphic in a sample from 2 U. pectinifera populations. The effective number of alleles ranged from 1.6 to 8.7, with an average per population of 3.3 (SE ± 0.30) and 4.5 (SE ± 0.50). Expected heterozygosity ranged from 0.375 to 0.847 and 8-10 loci showed departures from Hardy- Weinberg equilibrium in the analyzed populations. Based on the observed polymorphism level of each marker, as well as the analysis of null allele presence and evidence of amplification of duplicate loci, a subset of 12 loci can be used as reliable markers to investigate the genetic structure, diversity, and species limits of the Uebelmannia genus.

Genetic variability in esterases and the insecticide resistance in brazilian strains of Oryzaephilus mercator and Oryzaephilus surinamensis (Coleoptera: Silvanidae)

Oryzaephilus mercator and O. surinamensis are stored grains and processed food pests, the latter being responsible for major economical losses. Polyacrylamide gel electrophoresis was used to analyse esterase patterns during insect development. Seven esterases, three cholinesterases, two carboxylesterases and two acetylesterases, were identified in O. mercator, one of which was proper to adults. Five esterases, of which four were cholinesterases, occurred in O. surinamensis. Strains of O. mercator and O. surinamensis were also exposed to malathion and chlorpyrifos-methyl. According to the LC50 estimates, OmLC-M and OmLA strains of O. mercator and OsLB strain of O. surinamensis were the most resistant to both insecticides. However, higher sensitivity to malathion and chlorpyrifos-methyl has also been verified in some of its esterases. Cholinesterases OmEST-1 and OsEST-5 seem to be involved in this resistance. These results suggest that organophosphate tolerance may be related to genetic variability in esterase isoenzymes.