Influence of pH changes of aged insect attractants on the organophosphorus insecticide dimethoate, in spraying mixtures
1991
Rokofilou-Hourdakis, A. | Tzorbatzoudi-Anagnostopoulos, E. | Spyropoulos, S.G. (Benaki Phytopathological Inst., Kifisia (Greece). Lab. of Physical and Chemical Examination of Pesticides)
The pH change in mixtures of aged insect attractants and the organophosphorus insecticide dimethoate, with time and temperature was studied, in the proportions they are commonly used in Greece in bait sprays (preventive method) for the control of Dacus oleae and the influence of this change on the stability of dimethoate. The insect attractants Dacona, year of manufacture 1983 pH 8.45, Entomosyl of 1984, pH 9.02 and Dacus bait of 1985, pH 4.00 and an emulsifiable concentrate of dimethoate with active ingredient content 38% w/v, were used. Dacus bait (a hydrolysed protein) had maintained its initial acidic pH, two years after its manufacture, while for the other two non proteinic substances the initial slightly acidic to neutral pH (Dacona 6.1-6.7 and Entomozyl 6.2-6.6) had already changed to alkaline 4 and 3 years after their manufacture respectively. In the mixtures of Dacus bait and Dacona with dimethoate, no dimethoate degradation was observed. In the mixtures of Entomosyl with dimethoate a considerable degradation of dimethoate was observed, which was increasing with time and temperature.
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