Fans of this „royal vegetable“ can hardly wait for the beginning of asparagus season in mid-April. Whether the classic variant with po-tatoes and hollandaise sauce or as a gourmet concoction, the aver-age German eats about two kilos per year of this ivory-colored sea-sonal vegetable delicacy. As our analyses show, the enjoyment of this underground cultivated vegetable is rarely marred by pesticide residues.
07.08.2013 Asparagus – This Seasonal Vegetable Rarely Has Pesticide Residues Report from a day in the lab Fans of this „royal vegetable“ can hardly wait for the beginning of asparagus season in mid-April. Whether the classic variant with potatoes and hollandaise sauce or as a gourmet concoction, the average German eats about two kilos per year of this ivory-colored seasonal vegetable delicacy. As our analyses show, the enjoyment of this underground cultivated vegetable is rarely marred by pesticide residues. Summary In the years 2010 to 2013, 116 samples of asparagus (106 white and 14 green) were analyzed for the presence of over 650 pesticides. None of the analyses revealed exceedances of the maximum residue limits (MRL). However, 56 of the samples (48.3 %) were found to contain residues of various substances, among which 11 (9.5%) had multiple residues. The measured values were found overwhelmingly at trace levels under 0.01 mg/kg. In addition, 22 of the samples were analyzed for very polar sub- stances and their metabolites. Fortunately, only one sample was found with an excess of the MRL (fosetyl). Additionally, 10 asparagus samples were tested in 2013 for perchlorate, whereby no suspicious values were to be found. ADDRESS Schaflandstraße 3/2 70736 Fellbach E-MAIL Poststelle@cvuas.bwl.de PHONE +49 711 3426 - 1234 INTERNET www.cvua-stuttgart.de +49 711 3426 - 1727 (Diagnostics) FAX +49 711 588176 +49 711 3426-1729 (Diagnostics) Seite 2 von 9 Everything You Wanted to Know About Asparagus Description of the plant Asparagus is a monocotyledonous, herbaceous perennial that belongs to the asparagus family (Asparagaceae). At our latitude the genus Aspara- gus officinalis L is cultivated. Over the winter only the root stock (rhizome) survives in the soil, about 35 cm below the soil’s surface. In the spring several sprouts shoot up from the rhizomes, which grow in a raised, sandy mound where they stay pale and tender. As soon as the heads of the sprouts reach the surface the soil is pushed to the side and the white stalks are cut off with a hooked asparagus knife. In the sunlight the white asparagus stalks turn violet and finally green. The asparagus season officially ends on 24 June (the birthday of John the Baptist, closely connected to the onset of summer). After this, the remain- ing sprouts grow into up to two- meter high bushes that provide the rhizomes with the necessary nutrients for the following spring. Despite the adherence to a rest- Asparagus field in autumn. ing phase in summer and au- tumn, an asparagus field will be depleted after 10 to 12 years and can no longer be planted, even with new, cultivated rhizomes. Green asparagus differs mainly by the cultivation method. If no mound is formed, the sprouts grow on the flat soil and can then be harvested as green aspara- gus. Seite 3 von 9 left: an asparagus sprout pushes into the light; middle: harvesting; right: flat aspar- agus mound Origin and History Asparagus, a domestic European plant, was cultivated much earlier by the ancient Greeks. They used the dried roots as a diuretic. For the Romans asparagus was part of every feast. In the 17th century Ludwig XIV of France made asparagus into a popular culinary trend. But the break- through for this vegetable came only as it became possible to preserve asparagus in cans. And it was only in the 19 th century that asparagus changed its color. It was only by coincidence that the so-called “pale as- paragus” was discovered to be more tender to the taste. Since then, as- paragus in Germany has almost solely been grown “under the earth”. Culture The production of asparagus is lengthy and labor intensive. Asparagus thrives in light, sandy, water-permeable soil which, ideally, warms up quickly in the spring. The rhizomes, cultivated out of the red colored ber- ries, are planted in soil that has been deep-treated with fertilizer in the previous year. It takes three years before the asparagus can be harvest- ed for the first time. For pale asparagus a mound of earth will be built up over the rhizomes planted in rows. The mound must be well-flattened on top so the asparagus farmer knows in time when the asparagus must be harvested. A fine tear in the soil indicates the breakthrough of an aspara- gus sprout. The farmer must then carefully remove the soil from the sprout up to 35 cm deep, and then cut the sprout away with an asparagus knife. The surface of the mound must then be smoothed over again, so that Green asparagus. the next growing sprout is discovered be- fore it comes into the light. Seite 4 von 9 Asparagus grown on very large farms is harvested with special machines that, with help from lasers, find the ripe stalks and cut them completely automatically. Today asparagus is often cultivated under plastic. With clear plastic the starting point of the harvest can be controlled and, in gen- eral, ensue earlier. With black plastic the coloring of the asparagus can be prevented and the growth of weeds minimized. Green asparagus is less laborious – it grows up out of the flat ground and is harvested with a sharp knife when it has reached its correct height. Nutrients in Asparagus Asparagus contains a high amount of water (about 94%) and has a very low calorie count (13 kcal (52 kJ) per 100 gr asparagus). The heads are the most tender part and contain more vitamin C than the lower part of the stalk. The relatively high amount of free aspartic acid accounts for the typ- ical asparagus aroma. Pesticides in Asparagus Cultivation In Germany there are currently 13 fungicidal substances in various pesti- cides that are authorized for the treatment of the most significant aspara- gus foliage and root illnesses. Five insecticidal substances are permitted for use against the asparagus fly and other sucking and biting insects; 11 herbicides are authorized for use in the control of weeds and grasses dur- ing the various phases of asparagus cultivation. Table 1: Pesticides Authorized in Asparagus Cultivation in Germany, 2013 Fungicide Acaricide/Insecticide Herbicide Azoxystrobin Dimethoate Flufenacet Chlorthalonil Thiacloprid Metribuzin Boscalid Alpha-Cypermethrin Pendimethalin Epoxiconazole Lambda-Cyhalothrin Clomazone Copper hydroxide Pyrethrin Glyphosate Dithianon Dimethenamid-P Kresoxim-methyl Tepraloxydim Metiram Clethodim Iprodione Glufosinate Difenoconazole Bromoxynil Pyraclostrobin Pyridate Cyprodinil Fludioxonil Seite 5 von 9 Detailed Investigatory Results From 2010 to 2013, using the QuEChERS multi-method, 116 asparagus samples were analyzed for residues of over 650 pesticides. The largest portion of these samples (88%) consisted of white, so-called pale aspara- gus. Only 14 samples (7.1%) were green. Most of the samples came from Germany (67%), followed by Peru with 19%. Peruvian asparagus mainly comes onto our supermarket shelves when there is no fresh asparagus here (e.g. at Christmas). The good news up front: the investigations re- vealed no exceedances of the MRL. All of the findings were under the EU- wide established maximum limits (see Table 2). Table 2: Analyses of over 650 Pesticides with the QuEChERS Multi- Method Matrix No. Samples Samples w/ Samples > Samples w/ Residues Maximum Limit Multiple Residues Asparagus, 14 5 (35.7%) 0 1 (7.1%) green Asparagus, 102 51 (50.0%) 0 10 (9.8%) white TOTAL 116 56 (48.3%) 0 11 (9.5%) Residues under the ML were detected in 39.5 % of the German and in 75 % of the Peruvian asparagus samples, whereas 6.6% of the German and 20% of the Peruvian samples were contaminated with multiple residues (see Tables 3 und 4). Table 3: White Asparagus, by Country of Origin Country of No. Samples Samples w/ Samples > Samples w/ Multiple Origin Residues Maximum Limit Residues Germany 76 30 (39.5%) 0 5 (6.6%) Peru 20 15 (75%) 0 4 (20%) Spain 2 2 0 11 Greece 1 1 0 0 Italy 1 1 0 0 Morocco 1 1 0 0 Unknown 1 1 0 0 TOTAL 102 51 (50.0%) 0 10 (9.8%) 1 No percentage is given for sample quantities under 5. Seite 6 von 9 Table 4: Green Asparagus, by Country of Origin Country of No. Samples Samples w/ Samples > Samples w/ Origin Residues Maximum Limit Multiple Residues Spain 9 2 (22.2%) 0 0 Germany 2 2 0 1 Peru 2 0 0 0 Thailand 1 1 0 0 TOTAL 14 5 (35.7%) 0 1 (7.1%) Boscalid, a fungicide that is permitted for use in Germany on asparagus fields, accounted for the largest proportion of the findings. The fungicide was detected in 25 % of the samples, although mostly at trace levels un- der 0.01 mg/kg. Chlorpyrifos und imidacloprid, insecticides that are not approved in Germany for any plant protectors used in asparagus cultiva- tion, were detected in 12 % and 7 % of the samples respectively: none were from Germany, mostly from Peru. But also here the amount was mainly at trace levels of under 0.01 mg/kg, as with the other substances (see Table 5 and Illustration 1). Table 5: Pesticide Residues Pesticide Type w/ <0.01 <0.02 <0.05 Maxi- Samples Residues mg/kg mg/kg mg/kg mum > (mg/kg) Maximum Limit Boscalid Fungicide 29 27 2 0 0.016 0 Chlorpyrifos Insecticide 14 12 2 0 0.019 0 Imidacloprid Insecticide 8 8 0 0 0.008 0 Pendimethalin Herbicide 4 4 0 0 0.002 0 Cyprodinil Fungicide 3 2 0 1 0.03 0 Metribuzin Herbicide 2 2 0 0 0.004 0 Isoproturon Herbicide 1 1 0 0 0.001 0 Haloxyfop Herbicide 1 1 0 0 0.002 0 Fludioxonil Fungicide 1 0 0 1 0.028 0 Fenhexamid Fungicide 1 1 0 0 0.009 0 Dodine Fungicide 1 1 0 0 0.004 0 Diuron Herbicide 1 1 0 0 0.001 0 DDT Insecticide 1 1 0 0 0.002 0 Cypermethrin Insecticide 1 0 0 1 0.03 0 Bifenthrin Insecticide 1 0 0 1 0.024 0 2,6- Metabolite Dichlorbenzamide 1 1 0 0 0.001 0 Seite 7 von 9 Frequency of Detected Substances (>1) Metribuzin 2 Cyprodinil 3 Pendimethalin 4 Imidacloprid 8 Chlorpyrifos 14 Boscalid 29 0 5 10 15 20 25 30 35 Illustration 1:Frequency of Detected Substances (> 1) Among 116 Analyzed Samples Investigations with QuPPe Info Box QuPPe Pesticides with high polarity escape detection with use of the QuEChERS multi- I method. For these strongly polar substances we developed the QuPPe Method (Quick Polar Pesticides Method). The polar substances are extracted from homogenized plant-based foods with acidified methanol (w/ the addition of stable isotope-labeled standards, when nec.). After centrifugation the extract is filtered and the substances are identified by means of LC-MS/MS. Individual groups of polar pesticides are quantifiable with various LC-MS/MS methods (see also Table 6). The methods are continually updated and developed and applied to new substances. You can find more information on QuPPe on the Internet, at http://quppe.com/ . Due to the difficulty of finding highly polar pesticides using the normal mul- ti-methods, 22 asparagus samples were also analyzed for highly polar pesticides (see Table 5). Fortunately, only one sample contained a sub- stance in excess of the ML. This asparagus sample from Germany con- tained 3.4 mg/kg phosphorous acid. Phosphorous acid exists as a me- tabolite of fosetyl. The sum of fosetyl and phosphorous acid was over the EU-wide valid maximum limit of 2 mg/kg for these residues. These anal- yses of polar pesticides should be continued in 2014. Seite 8 von 9 Table 6: QuPPe Substances and their Mode of Action Pesticide Type Insecticide from cartap, bensultap, Nereistoxin thiocyclam or thiosultap Difenzoquat Fungicide/Herbicide Cyromazine Insecticide Chlormequat Plant growth regulator Mepiquat Plant growth regulator Chlormequat Plant growth regulator Glyphosate Herbicide Fosetyl Fungicide Ethephon Plant growth regulator HEPA Ethephon-Metabolite Maleic acid hydrazide Plant growth regulator Glufosinate ammonium Glufosinate-Metabolite Daminozide Plant growth regulator Phosphorous acid Fosetyl-Metabolite AMPA Glyphosate-Metabolite N-Acetyl-AMPA Glyphosate-Metabolite Glufosinate Herbicide MPPA Glufosinate-Metabolite N-Acetyl-Glufosinate Glufosinate-Metabolite Trimethylsulfonium-Cation Glyphosate-Counterion Diquat Herbicide Paraquat Herbicide In 2013 perchlorate und chlorate were integrated into the QuPPe method. Ten samples of asparagus were also tested for these substances; the measures values for all the samples were unremarkable. Literature: Franke, Wolfgang (1997) Nutzpflanzenkunde, Thieme Verlag Stuttgart Wyk, van Ben-Erik (2005) Handbuch der Nahrungspflanzen, Wis- senschaftliche Verlags GmbH Stuttgart Bickel-Sandkötter (2003) Nutzpflanzen und ihre Inhaltsstoffe, Quel- le & Meyer Verlag Wiebelsheim Pflanzenproduktion 2013, Pflanzenschutz im Erwerbsgemüsebau, LTZ Augustenberg, www.ltz-augustenberg.de Pflanzenschutzmittel-Verzeichnis 2013, 61. Auflage, BVL, http://www.bvl.bund.de Seite 9 von 9 Photo Credits: Asparagus, val th, ClipDealer.com, Image-ID=268570. Dem Licht entgegen, Silke Bogorinski, Pixelio.de, Image-ID 651128. Spargelfeld im Herbst, moorhrmr, Pixelio.de, Image-ID 193516. Spargelzeit: Spargelernte 06, Thommy Weiss, Pixelio.de, Image-ID 460395. Spargelstecher, Jürgen Sörensen, Pixelio.de, Image-ID 261472. Grüner Spargel, Hubert Zipper, CVUA Stuttgart. Authors: Dr. Ingrid Kaufmann-Horlacher, Ellen Scherbaum, Carmen Wauschkuhn
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