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  • Author or Editor: Parshall B. Bush x
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To discern how the packing process influences pesticide residue loads on peach (Prunus persica L. Batsch) fruit; postharvest, post hydrocooled, and post brushed fruit were assessed for levels of several pesticides. The packing house process reduced pesticide residue levels on fresh peaches to levels that were generally below detection limits of our assays in 1998. Carbaryl and captan residues from field packed fruit were 32.2× and 21.9×, respectively, of that found in the peel of fruit processed in the packing house in 1998. Carbaryl levels were not reduced by hydrocooling but postharvest brushing reduced pesticide residues up to 94% in fruit peel. Across processing operations and cultivars assessed in 1999, hydrocooling, hydrocooling plus brushing, and brushing alone removed 37%, 62%, and 53%, respectively, of the encapsulated methyl parathion residues from fruit peel. Hydrocooling had the greatest impact on phosmet removal from peel, reducing levels by 72.5%. After hydrocooling, phosmet was 5.7× following brushing in one-half of the subsequent samples. This increase occurred at all three farms, suggesting that periodic cleaning of brushes may be necessary to prevent later contamination of peach peel with pesticides. In the only example in which propiconazole residue remained on peaches at picking, it was removed most effectively (69%) by the brushing operation. Nearly 31% of the propiconazole was removed in the hydrocooler. The packing process before shipment to retail outlets was generally effective in the removal of pesticides that may be present on peel at the time of harvest. Assessment of pesticide residue levels in peach flesh was uniformly below the levels of detection in our assays, suggesting that the classes of pesticide analyzed in peaches were not transepidermal.

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The effectiveness of the s-triazines simazine [2-chloro-6-bis (ethylamino)-s-triazine] and atrazine [2-chloro-6-(ethylamino)-6-(isopropylamino)-s-triazine and nitrapyrin [2-chloro-6-(trichloromethyl)pyridine] in suppressing denitrification was evaluated in laboratory and greenhouse studies. Parameters used to measure suppression of denitrification were N2 and N2O evolution, soil NO3-N, and plant N (% N × dry weight). Simazine and atrazine significantly reduced N2O evolution in laboratory incubation studies, but had no effect on N2 evolution, while nitrapyrin reduced both N2 and N2O evolution. In greenhouse studies, 0.5 mg kg-1 soil of simazine and atrazine, and 2.0 mg kg-1 soil of nitrapyrin increased soil NO3-N and plant N as compared to the control. It is concluded that simazine and atrazine inhibited denitrification under greenhouse and laboratory conditions and, therefore, that increased media NO3-N availability is the most likely explanation why N concentration in the plant tissue was higher.

Open Access