Pesticide residues quantification in frozen fruit and vegetables in Chilean domestic market using QuEChERS extraction with ultra-high-performance liquid chromatography electrospray ionization Orbitrap mass spectrometry.

Pesticide residues on foods are a global concern due to the impact on human health. Many countries have adopted regulations to establish Maximum Residue Levels (MRLs) to control use of pesticides. This study aimed to determine pesticide residues in frozen fruit and vegetables from Chilean retail stores using UHPLC-Orbitrap MS and QuEChERS™ multiresidue-extraction kit. 237 samples of frozen produce were sampled from different supermarkets and times during the year. Abamectin, Chlorpyrifos, Imidacloprid, Iprodione, λ-cyhalothrin, Spinosad A, and Spinosad D were quantified. Results showed that Iprodione, Spinosad A, and D were the most detected molecules. Pesticides were detected in 96.6% of samples and 21 samples exceeded MRL. Corn and faba beans showed the highest concentration of Iprodione with an average of 6.7 and 5.4 mg/Kg, respectively. Existence of nonconformity in samples highlights the importance to control pesticide residues of Chilean frozen produce, since it represents a latent health threat on consumers.

Digital cover photography for estimating leaf area index (LAI) in apple trees using a variable light extinction coefficient.

Leaf area index (LAI) is one of the key biophysical variables required for crop modeling. Direct LAI measurements are time consuming and difficult to obtain for experimental and commercial fruit orchards. Devices used to estimate LAI have shown considerable errors when compared to ground-truth or destructive measurements, requiring tedious site-specific calibrations. The objective of this study was to test the performance of a modified digital cover photography method to estimate LAI in apple trees using conventional digital photography and instantaneous measurements of incident radiation (Io) and transmitted radiation (I) through the canopy. Leaf area of 40 single apple trees were measured destructively to obtain real leaf area index (LAI(D)), which was compared with LAI estimated by the proposed digital photography method (LAI(M)). Results showed that the LAI(M) was able to estimate LAI(D) with an error of 25% using a constant light extinction coefficient (k = 0.68). However, when k was estimated using an exponential function based on the fraction of foliage cover (f(f)) derived from images, the error was reduced to 18%. Furthermore, when measurements of light intercepted by the canopy (Ic) were used as a proxy value for k, the method presented an error of only 9%. These results have shown that by using a proxy k value, estimated by Ic, helped to increase accuracy of LAI estimates using digital cover images for apple trees with different canopy sizes and under field conditions.