EFFECT OF DIMBOA ON GROWTH AND DIGESTIVE PHYSIOLOGY OF SESAMIA NONAGRIOIDES (LEPIDOPTERA, NOCTUIDAE) LARVAE

The hydroxamic acid 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3 (DIMBOA) was assessed for its effect on growth and digestive physiology of larv ae of the stalk corn borer Sesamia nonagrioides Lef. Nutritional indic es and activities of some digestive and detoxification enzymes were de termined for larvae feeding on a DIMBOA-containing diet for the first two days of the third instar (short-term feeding assays), and from neo nates to third instar (longterm feeding assays). DIMBOA reduced the re lative growth rate and the efficiency of conversion of ingested food w ithout affecting the relative consumption rate in long-term feeding as says, but it had no effect in short-term assays. Moreover, elastase-li ke activity was significantly increased by DIMBOA in short-term feedin g assays, whereas microsomal oxidase activity was increased and estera se activity was reduced in long-term feeding assays. In vitro, DIMBOA inhibited the activities of carboxypeptidases, aminopeptidase, glutath ione S-transferase and esterase, but it had no effect on trypsin, chym otrypsin and elastase, The implications of the altered levels of prote ases and detoxification enzyme activities on the digestive physiology of larvae feeding on DIMBOA-containing diets are discussed. (C) 1998 E lsevier Science Ltd. All rights reserved.