Effects of azadirachtin after systemic uptake into Brassica oleracea on larvae of Pieris brassicae

Abstract

AbstractPetioles of intact cabbage leaves were placed in azadirachtin solutions for 24 h. Azadirachtin or active metabolites of this compound appeared to be translocated systemically as performance of first instar larvae of Pieris brassicae L. placed on disks from those leaves was affected. The position within a leaf from which disks were excised did not affect the extent of these effects, indicating a homogeneous distribution of active compounds in the laminar tissue. At doses ranging from 1–10 ppm of azadirachtin in the solution taken up by the leaves, gain of larval fresh weight and leaf area consumed were reduced. These effects were dose dependent up to 60–90 ppm. At 10 ppm and higher doses no larva reached the second instar within 72 h. Mortality during the 72 h period was highest at 10 ppm, due to the coincidence of lethal action with ecdysis in combination with the effect on developmental rate. Azadirachtin solutions applied directly to the surface of leaf disks in order to produce known doses on a leaf fresh weight basis gave results similar to the systemic treatment for weight gain, leaf area consumed and developmental rate, while mortality was higher in the latter treatment.