Dynamics of canopy-dwelling arthropods under different weed management options, including glyphosate, in conventional and genetically modified insect-resistant maize.

The use of genetically modified varieties tolerant to herbicides (HT varieties) and resistant to insects (Bt varieties) in combination with application of a broad-spectrum herbicide such as glyphosate could be an effective option for the simultaneous control of weeds and pests in maize. Nevertheless, the possible impact of these tools on nontarget arthropods still needs to be evaluated. In a field study in central Spain, potential changes in populations of canopy-dwelling arthropods in Bt maize under different weed management options, including glyphosate application, were investigated. Canopy-dwelling arthropods were sampled by visual inspection and yellow sticky traps. The Bt variety had no effect on any group of studied arthropods, except for the expected case of corn borers-the target pests of Bt maize. Regarding the effects of herbicide regimes, the only observed difference was a lower abundance of Cicadellidae and Mymaridae on yellow sticky traps in plots not treated with pre-emergence herbicides. This effect was especially pronounced in a treatment involving two glyphosate applications. The decrease in Cicadellidae and Mymaridae populations was associated with a higher density of weeds in plots, which may have hindered colonization of the crop by leafhoppers. These differences, however, were only significant in the last year of the study. The low likelihood of the use of glyphosate- and herbicide-tolerant varieties for weed control triggering important effects on the nontarget arthropod fauna of the maize canopy is discussed.

Field evaluation of 3-hydroxy-2-hexanone and ethanol as attractants for the cerambycid beetle pest of vineyards, Xylotrechus arvicola.

BACKGROUND: The beetle Xylotrechus arvicola (Coleoptera: Cerambycidae) is a serious pest of vineyards in the Iberian Peninsula. In previous work, the male beetles, but not females, were shown to produce (R)-3-hydroxy-2-hexanone, and female beetles were attracted to this compound in a laboratory bioassay. In this study, release rates of 3-hydroxy-2-hexanone from different dispensers were measured in the laboratory, and the attractiveness of these to X. arvicola adults was determined in trapping tests in three traditional wine-growing regions in Spain. RESULTS: As a result of laboratory experiments, for field experiments 3-hydroxy-2-hexanone was formulated as 100 µL in a polyethylene sachet (50 mm × 50 mm × 250 µm), and ethanol was formulated as 1 mL in a polyethylene press-seal bag (76 mm × 57 mm ×50 µm). Field catches were similar at all three study sites. Catches in traps baited with 3-hydroxy-2-hexanone alone were not significantly different from those in unbaited control traps, but catches in traps baited with 3-hydroxy-2-hexanone and ethanol in separate sachets, with 3-hydroxy-2-hexanone and ethanol in the same sachet or with ethanol alone were significantly greater than those in control traps. These results confirm that the beetles are attracted to ethanol, and the addition of 3-hydroxy-2-hexanone does not seem to make any difference. CONCLUSIONS: Attraction of females for the male-produced compound (R)-3-hydroxy-2-hexanone has been observed in laboratory but not in field experiments. Traps baited with ethanol are highly attractive to both sexes of adults of X. arvicola, and these can be used for improved monitoring of the adult emergence and for population control by mass trapping. © 2016 Society of Chemical Industry.

Laboratory evaluation of alternative control methods against the false tiger, Monosteira unicostata (Hemiptera: Tingidae).

BACKGROUND: Monosteira unicostata is an important pest of almond tree in the Mediterranean region requiring control methods alternative to synthetic pesticides. The efficacy of kaolin, azadirachtin and potassium salts of fatty acids combined with thyme essential oil against adults and fourth instar nymphs of this tingid was evaluated in laboratory assays. RESULTS: In no choice assays with adults, kaolin significantly increased mortality compared to control (42.7% versus 23.8%) and reduced the oviposition of females (11.8 versus 35.3 eggs), the feeding activity (169.6 versus 471.2 excrements) and the damage caused (1.1 versus 2.3 damage index). In choice assays with adults, the repellence index calculated for kaolin (48.2%) was significantly higher compared to control (-15.3%), resulting in oviposition, feeding and damage deterrence indices also significantly higher than the control. In no choice assays with nymphs, all products increased mortality and reduced the feeding activity and the damage caused on leaves. Potassium soap with thyme essential oil and azadirachtin were the most effective compounds (98.0% and 97.6% mortality versus 13.3% control mortality, respectively). CONCLUSION: The products tested have shown high and different efficacy on nymphs and adults of Monosteira unicostata. This activity might be suitable for the practical application of these compounds to control its populations under real field conditions.

Laboratory tests of insect growth regulators as bait sprays for the control of the olive fruit fly, Bactrocera oleae (Diptera: Tephritidae).

BACKGROUND: Insect growth regulators (IGRs) act specifically on arthropods. This selectivity makes them an interesting alternative to traditional insecticides for pest control. The aim of this work was to test the IGRs azadirachtin, cyromazine, flufenoxuron, lufenuron and pyriproxyfen as useful pesticides for the control of the olive fruit fly, Bactrocera oleae (Rossi), a key pest of olive crops. RESULTS: Of the products tested, the chitin-synthesis inhibitor lufenuron showed the highest efficacy. The life parameter showing the strongest effect was the egg hatch, because lufenuron caused nearly 100% egg mortality 7 days after treatment. However, sterility was not transmitted from the treated males to the untreated females. The LC50 and LC90 values for a 7 day evaluation period were 19.3 and 86.2 µg AI mL(-1) respectively. Azadirachtin, cyromazine and flufenoxuron also caused significant increases in egg mortality. However, these increases were less than those produced by lufenuron. Pyriproxyfen had a stimulatory effect on B. oleae fecundity. CONCLUSION: Applied as a bait treatment, a procedure used frequently in the field for the control of B. oleae, lufenuron is potentially useful against this important pest.

Bioaccumulation assessment via an adapted multi-species soil system (MS.3) and its application using cadmium.

This paper presents an experimental design for quantifying the transfer of chemicals at low trophic levels of terrestrial ecosystems. The soil microcosms, MS.3(foodchain) (food chain multi-specie soil system) covered the transfer from soil to earthworms (Eisenia fetida) and from soil to plant (Triticum aestivum), then to phytophagus (Rhopalosiphum padi) and finally predator (Chrysoperla carnea) species. Cadmium was used as model pollutant. Cadmium accumulation in foliar invertebrates was related to the species biology. A significant transfer of this metal through the minimized food chain was found for all species, but not a biomagnification in the predator species. Results pointed out the relevance of foliar invertebrates and their trophic relationships as additional exposure routes for assessing secondary poisoning in predators. Hence, MS.3(foodchain), could be applied for terrestrial environmental risk assessment when potential bioaccumulation could be expected.