Effect of Combination Treatments of Gamma Radiation and Methyl Bromide Fumigation on the Confused Flour Beetles Tribolium confusum Duv.

Abstract

A laboratory study was carried out in Egypt to determine the effect of combining treatments of gamma radiation and methyl bromide fumigation applied to adults of Tribolium confusum (Duv.). An interaction between irradiation and insecticidal treatment was obvious, with additive effects noted at most combination treatments. When the irradiation treatments were applied first and fumigation were accomplished within 24 hr., the intermediate dosage of irradiation (6 krad) afforded the insects some protection against marginally effective dosages of methyl bromide after 14 days. On the contrary, it is evident that a possible synergistic effect of irradiation pretreatment followed by chemical exposure, after 21 days, where all of irradiation dosages used (2–10 krad) enhanced the fumigant effectiveness. On the other hand, when the irradiation dosages were increased from 5–50 krad and followed by fumigant treatments after 7 days, the trend did continue where all combination treatments killed more insects than did either treatment applied alone. Conversely, when fumigation preceded treatment with irradiation the sublethal methyl bromide fumigation also apparently leaves the surviving insects in a debilitated state and became more radiosensitive.

In general, the effects from combination of irradiation and fumigation were more effective than were the effects of either treatment given singly, whether irradiation preceded insecticidal treatment or vice versa.

Résumé

Etudes de laboratoire ont été réalisé en vue de la determination de l’effet combiné de la radiation de gamma et la fumigation de bromide de methyle sur les adultes de T. confusum (Duv). Une interaction entre la radiation et le traitement d’insecticide a e’té remarque, l’effet éditif a été aussi observé pour la majorité des traitements combinés. Si la radiation est effectué d’abord; et la fumigation 24 hrs plus tard, les doses trés réduits de la radiation (2-6 krad) protége les insectes contre l’effet marginale de bromide de methyle aprés 14 jours. D’antre part, si le dosage de la radiation augment de 5 a 50 krad, suivi par le traitement de fumigant 7 jours aprés, on observe que les traitements combines tuent plus d’insectes que l’application de chaque traitement seul. Par contre, si la fumigation precede l’irradiation, le fumigant rend les insectes survivants plus sensible pour l’effet de la radiation.