Toxicity of essential oils, synthetic antioxidants and natural phytochemicals to three storage insect vectors of Aspergillus flavus

ANDREA NESCI; PAULA BARRA; M. ALEJANDRA PASSONE; MIRIAM ETCHEVERRY

Tulln, Austria

Conferencia; ISM Conference 2009. Wordlwide Mycotoxin Reduction in Food and Feed Chains.; 2009

International Society for Mycotoxicology

The purpose of the present study was to investigate the insecticidal activity of 2(3)-tert-butyl-4 hydroxyanisole (BHA); 2,6-di (tert-butyl)-p-cresol (BHT); 3-phenyl-2-propenoic acid (CA), trans-4-hydroxy-3-methoxycinnamic acid (FA); and essential oils of Eugenia caryophyllata (clove tree) and Thymus vulgaris (thyme) against Sitophilus oryzae (L.), Tribolium confusum (Jacquelin du Val) and Rhyzopertha dominica (F.) that may act as carriers of aflatoxigenic fungi on stored maize. One mL of 104 spores/mL of Aspergillus flavus strain was applied to 500 g maize in 500 mL plastic jars and 20 adults of insects were added to maize. All compounds were added separately to maize at different dose: BHA 20 mM, BHT 20 mM, BHA+BHT 20+20 mM, CA 25 mM, FA 30 mM, CA+FA 25+30 mM, essential oils of E. caryophyllata and  T. vulgaris 2000 and 3000 ppm. Over exposure period used was 120 days under controlled conditions (28±1ºC, 70±5% r.h., in darkness). Each experiment was repeated three times. The weight loss of maize, susceptibility of insects, Aspergillus isolation frequency from insects and maize, and aflatoxin B1 analyses from maize were determined. Maize infested with S. oryzae without insecticidal compounds (control treatments) was significantly more damage than controls infested with the other insects. No significant differences were observed between fresh weights of treatments with insecticidal compounds. BHA and BHT alone and in mixture showed a high insecticidal activity (100% mortality) at 120 days against S. oryzae, T. confusum and R. dominica. The same effect was observed with FA and the mixture FA+CA. The three stored insects used were resistent to all dose of essential oils assayed, however the number of insects recovered was lower tan the number recovered in control treatments. The higher percentage (79%) of A. flavus contamination was observed in control treatments infested with S. oryzae. Three stored insects proved showed a low susceptibility to all dose of essential oils assayed, and insects that survived had a range of A. flavus incidence between 0 to 34%. These results showed that three stored insects had the ability to disperse the toxigenic fungus A. flavus on storage maize. The analyses of aflatoxin B1 showed that this toxin was present only in maize infested with R. dominica and treated with essential oil of clove tree (2.6 ppb). Essential oils and natural phytochemicals showed toxicity to the three storage insects, however synthetic antioxidants BHA and BHT alone and in mixture were 100% effective in killing these insects.