The effect of application timing of metconazole on the control of Fusarium head blight (HFB) and mycotoxin accumulation in wheat and barley was investigated. Single and double applications of metconazole at different spray timings were performed in a wheat field trial. In single application plots, the mid-flowering stage was the optimal application timing of metconazole for controlling FHB symptom development, and the milking stage was optimal for reducing mycotoxin contamination. Similar efficacies were observed in all spray timings in double application plots, which included the mid-flowering stage and another spray timing. In the barley field trial, application at the mid-flowering stage controlled both FHB development and mycotoxin contamination with the highest efficacy. Similar efficacies for controlling the development of FHB in the barley field were observed with single and double applications of the fungicide. However, mycotoxin contamination was lower with double application than with single application of the fungicide.
Spodoptera exigua is a major insect pest of vegetables in Shandong, China, and has been reported to develop resistance to many insecticides. The present study was carried out in 2011–2012 to evaluate the resistance ratios (RRs) to eight insecticides in S. exigua populations from five regions in Shandong. A standard leaf-dip method showed no resistance to chlorfenapyr (RR <2). RRs to emamectin benzoate, indoxacarb, and spinosyn were in the ranges of 3.00 to 37.4-fold, 8.63 to 84.1-fold, and 9.27 to 86.2-fold, respectively. S. exigua showed high resistance to the insect growth regulators (IGR) tebufenozide and methoxyfenozide. No resistance to the diamide insecticides chlorantraniliprole and flubendiamide was found. The insecticides chlorfenapyr, emamectin benzoate, indoxacarb, spinosyn, chlorantraniliprole, and flubendiamide had no, very low, low, and moderate resistance levels for most of the tested populations. Due to these characteristics they could be used in pest management programs supplemented with physical and biological control measures.
A series of spray experiments was conducted in order to determine deposition at different heights of the hedgerow and to estimate the effect of unsprayed buffer zones on spray deposition. Deposition varied highly with distance, absolute humidity, height, droplet size distribution and wind speed. Eighty-two percent of the observed variation could be accounted for by these factors. Droplet size distribution depended on nozzle type and working pressure, which confirms the potential of these factors for reducing spray drift. Unsprayed buffer zones reduced deposition in hedgerows, but the effect was more pronounced in the lower parts, where a reduction of 72% was obtained by introducing a 12 m buffer zone, whereas at 4 m height the reduction was less than 1%. Therefore, deposition at different heights of the hedgerow should be included in order to make risk assessments relevant for organisms exploiting different parts of the hedgerow.
Pyroxasulfone behavior in prairie soils was evaluated using a 7-day sugar beet (Beta vulgaris L.) shoot length inhibition bioassay. Pyroxasulfone bioactivity in soil, assessed from 0 to 184 g a.i./kg, was primarily related to organic carbon content (p=0.001) with decreased bioactivity occurring in soils of high organic carbon. Pyroxasulfone bioactivity, measured after soil pH adjustments, was reduced as soil pH decreased demonstrating that at low soil pH pyroxasulfone becomes less available to plants. Pyroxasulfone half-lives estimated for dissipation at 25°C and moisture content of 85% field capacity ranged from 16 to 69 days. Organic carbon content (p=0.034) and soil pH (p=0.008) were significant in affecting pyroxasulfone half-lives with faster dissipation occurring in soils of high organic carbon content and high pH. Interactions between soil-incorporated pyroxasulfone and sulfentrazone were either antagonistic or additive and the nature of these interactions could vary with soil type.
Eighty apple samples with protected geographical indication (PGI) or designation of origin (PDO) were analyzed for 51 target pesticides using the “quick, easy, cheap, effective, rugged and safe” (QuEChERS) method. Accuracy and precision were evaluated by means of recovery experiments at four concentration levels (10–250 µg/kg). Twelve pesticide residues were detected in 75 positive samples with an average number of detected pesticides per sample equal to 6.0. The highest detection rates were observed for chlorpyrifos (n=75), quinalphos (n=75) and parathion (n=73). Only 2 of the 80 investigated samples contained pesticide residues (parathion-methyl) in levels exceeding the maximum residue limits (MRLs). According to Spearman correlation analysis, the most powerful correlations were obtained between α-endosulfan and β-endosulfan (r=0.823) and between flufenoxuron and penconazole (r=0.683). Principal component analysis revealed similarities in the pesticides levels of all PDO/PGI samples, while the kind of product also significantly impacts its residue content.
To evaluate the effects of sample-size reduction and separate analyses of fruit pulp and peel, residual levels of 3 pesticides in watermelons and muskmelons were determined. The pesticide residue levels in 2 types of size-reduced samples were compared. In one size-reduced sample, the pesticide residues in the pulp with the peel were analyzed (A). In the other size-reduced sample, residues in the pulp and peel were analyzed separately. Afterward, the pesticide residue levels were calculated for the whole fruit (B). The majority of the pesticide residues were found to be present in the peel. The mean percent differences (A/B±standard deviations [SD]) of pesticide residue levels in the watermelon and muskmelon samples were 91±15% and 83±11%, respectively. No significant effect of sample-size reduction and separate analyses of pulp and peel were found in determining the pesticide residues in large-sized fruiting vegetables.
The efficacy of a new fluorinated benzamide compound LH-2010A against Pseudoperonospora cubensis and its uptake-translocate behavior in cucumber plants were studied. Calculated EC50 was 6.70 µg/mL, whereas fluopicolide was 7.67 µg/mL. LH-2010A was absorbed by plants and translocated to other sites. Furthermore, the downward transportation observed was different from fluopicolide. The absorption of LH-2010A by cucumber roots was inhibited by low temperature, respiratory inhibitors, sucrose and amino acids indicating that the absorption is an active process.
The anticholinesterase activity of four biochemical pesticides: spinosad, pyrethrum, neem bark extract and veratrine was tested against one acetylcholinesterase extracted from Electrophorus electricus and two from Drosophila melanogaster. Pyrethrum, neem bark extract, and veratrine induced a dose-related inhibition of a variable type. Electric eel cholinesterase was inhibited uncompetitively by neem bark extract, the inhibition of the wilde-type fruit fly enzyme by pyrethrum was competitive, and the other enzyme-biochemical pesticide inhibitions were non-competitive. The sensitivity of each enzyme toward biochemical pesticides was variable.