Volatiles released from cotton plants in response to Helicoverpa zea feeding damage on cotton flower buds

Feeding of Helicoverpa zea larvae on cotton (Gossypium hirsutum L.) flower buds (squares) for 24 or 48 h induced the release of a number of terpenes [(E)-beta-ocimene, linalool, (E)-beta-farnesene, (E,E)-alpha-farnesene, (E)-4,8-dimethyl-1,3,7-nonatriene, (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene], isomeric hexenyl butyrates, 2-methylbutyrates, indole and (Z)-3-hexenyl acetate. These compounds are not released in significant amounts from undamaged squares and freshly damaged squares. The release of inducible compounds was not limited to the damaged squares themselves. The compounds were also released systemically from the upper undamaged leaves of the same plant after 72 h. However, the composition of the blend of systemically released volatiles differed from the blend released by damaged squares. The compounds that were systemically released from undamaged leaves in response to feeding on the squares were (Z)-3-hexenyl acetate, (E)-beta-ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, (E)-beta-farnesene, (E,E)-alpha-farnesene, and indole. This study shows that insect damage inflicted to the reproductive parts of a plant causes a systemic emission of volatiles from its vegetative parts.