Toxicity and toxicokinetics of 6-methoxybenzoxazolinone (MBOA) in the European corn borer, Ostrinia nubilalis (Huebner)

The maize-derived secondary chemical 6-methyoxybenzoxazolinone (MBOA) and a tritiated derivative were prepared synthetically for a detailed examination of their toxicity and toxicokinetics in the European corn borer (ECB), Ostrinia nubilalis. During feeding trials with MBOA incorporated into meridic diets, the mean time population and adult emergence was significantly lengthened at concentrations of 1.5 mg MBOA/g diet and above. Increased mortality occurred at concentrations at 1.5 mg/g and above. A decrease in the sex ratio (female/total) and fecundity was observed at concentrations of 0.5 mg/g and above. The latter observations represent new biological effects related to MBOA. In tracer studies, both uptake and excretions of MBOA administered in diets to larvae increased linearly with concentration. Body burden values indicated that the ECB larvae were capable of excreting enough compound to maintain total tissue levels at approximately 50% of the dietary concentration. Total amount of label increased with larval stage, but decreased in adults due to a large amount of label eliminated in the pupal case. In topical application studies, elimination of the label in the frass was rapid, reaching 60% by 6 hr and 82% of applied dose by 24 hr. Accumulation of label in tissues other than hemolymph was small. The results show that MBOA is toxic to ECB, but the insect has efficient methods for minimizing these effects