Gall insects can avoid and alter indirect plant defenses

Area of Science:

• Ecology
• Evolutionary Biology
• Chemical Ecology

Background:

• Parasites can manipulate host traits, sometimes to their own benefit.
• Gall-inducing insects are known to alter host plant morphology, physiology, and chemical defenses.

Purpose of the Study:

• To investigate if gall-inducing insects alter indirect plant defenses, specifically volatile compound release.
• To determine if volatile production is altered in response to different insect herbivores.

Main Methods:

• Field and laboratory experiments were conducted on goldenrod (Solidago altissima).
• Volatile production was measured in response to attacks by gall-inducing insects (Eurosta solidaginis, Gnorimoschema gallaesolidaginis), spittlebugs (Philaenus spumarius), and a generalist caterpillar (Heliothis virescens).

Main Results:

• Heliothis virescens elicited strong indirect defensive volatile responses from S. altissima.
• Gall-inducing species and spittlebugs did not elicit significant volatile responses.
• Infestation by E. solidaginis suppressed volatile responses to subsequent caterpillar attack.

Conclusions:

• Gall-inducing insects, particularly E. solidaginis, exert significant control over host plant defense mechanisms.
• Suppression of volatile defenses may reduce predation risk for gall-inducers and influence plant-insect community dynamics.