Submitted to: International Journal of Allelopathy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 17, 1997
Publication Date: N/A
Interpretive Summary: The corn earworm is an economically important pest of many crops in North and South America. Chemists and natural product scientists have shown an interest in exotic plant materials as sources of new chemicals for possible use in reducing losses in crops by insect pests. Dogwood, hydrangea, black cherry and Bradford pear leaves were fed to larvae of the corn earworm to discover possible new chemicals that inhibit their growth and development. Corn earworm tested as young larvae did not perform well after having fed on leaves of these nonhosts. When larger larvae were fed the leaf- diets, the results indicated that leaves of hydrangea possess a toxic factor and that leaves of the dogwood, black cherry and Bradford pear have a severe growth retardant for larvae of the corn earworm. Thus, these nonhosts contain chemicals that offer a potential for extraction and identification for possible use in controlling larvae of the corn earworm on crops.
Laboratory bioassays were conducted with neonate and 5th instars of the corn earworm, Helicoverpa zea (Boddie), (CEW) fed on a standard diet alone and on a diet amended with celufil or leaves from dogwood, Cornus florida L., hydrangea, Hydrangea macrophylla (Thumb.) Seringe, black cherry, Prunus serotina Ehrh., or Bradford pear, Purus calleryna Decne. Neonates grew less and produced less frass when fed diets containing leaves of dogwood, hydrangea, black cherry and Bradford pear leaf-diets. Fifth instars consumed less and weighed less when fed the hydrangea leaf-diet. The approximate digestibility of hydrangea and pear diets by 5th instars was significantly lower than the approximate digestibility of other treatments. The efficiency of conversion of digested dogwood and cherry was lower than regular diet and the hydrangea leaf-diet. The results also indicated that leaves of dogwood have a feeding deterrent and that leaves of black cherry and Bradford pear have factors that adversely affect the growth of neonates. The leaves of hydrangea possess a strong feeding deterrent for 5th instars that also is highly toxic to neonates. Isolation, identification, and characterization of chemicals from the leaves of these plants may provide a novel means of control of this important pest.