Laboratory and field efficacy of neem (Azadirachta indica A. Juss) extracts against two broccoli pests
1993
Prijono, D. (Bogor Agricultural Univ., Bogor (Indonesia). Dept. of Plant Pests and Diseaes) | Hassan, E.
This study was conducted to test the growth-regulating activity of neem extract of the cabbage webworm Crocidolomia binotalis Zeller ( Lepidoptera: Pyralidae) and to evaluate the field efficacy of the extract against the diamondback moth Plutella xylostella (L.) (Lepi- doptera: Yponomeutidae) and against C. binotalis on broccoli plants. In the laboratory, third- and fourth-instar larvae of C. binotalis fedbroccoli leaves treated with neem extract or azadirachtin for 24 h and48 h, respectively, and then their development was followed until pupation or adult emergence. Metamorphic effects of neem extract of the fourth instar of the course of its development to the adult stage wereclassified into five categories: 1) the fourth-instar larva died before or during pupation, 2) malformed pupa, 3) the larva successfully pupated but died before adult emergence, 4) malformed adult or the adult did not eclose completely from the pupal case, and 5) normal adult. The quantitative data for these effects were subjected to polytomous binary response analysis based on the conditional model. The results revealed that the conditional probability of occurrence of the effect in all categories was concentration-dependent, and this suggests that neem extract exerts strong metamorphic disturbances in the developement of the test insect. The median moulting inhibitory con- centration (IC 50) of neem extract and azadirachtin against the third instar was 0.27 % and 43.9 g/l, respectively, and that of neem extract against the fourth instar was 0.065 %. In the field, the treatment with neem oil (azadirachtin: 2.5 % w/v) at rates of 1.8, 2.4, and3.0 l/ha provided comparable protection to broccoli plants from infestation by P. xylostella as that with sumicidin 200 EC (fenvalerate 50 g/ha). In addition, the same treatments could check,
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