Trirhabda canadensis

Diterpenoids have a wide range of biological activities. Their role in plant-insect interactions, both as antifeedants and growth inhibitors, is reviewed. Four ent-kauranes, kaur-16-en-19-oic acid, (-)-kauran-l > -ol, 15 t-hydroxy-(-)-kaur-16-en-19-oic acid, and 17-hydroxy-(-)-kaur-15-en-19-oic acid, have recently been isolated from the leaves of Solidago nemoralis.These compounds were found to have antifeedant activity against Trirhabda canadensis. 

Most previous experiments with kauranes and closely related compounds have been concerned with their effects on Insect growth and development. However in this case the deterrent effects of the Isolated compounds to Trirhabda canadensis were investigated as a first step in understanding the feeding behavior of this insect in the field. 

However these compounds either singly or in combination do not account for the total lack of feeding activity observed either in the laboratory or in the field. Resistance of S. nemoralis to Insect attack seems to Involve, as is expected, not a single class of compounds but a multichemical response. Other compounds isolated from nemoralis showing antifeedant activity to Trirhabda canadensis are at present under investigation. 

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