Evidence for long‐distance, chemical gall induction by an insect

Abstract

We report that a chemical stimulus from a herbivore, a galling insect, changes plant morphology and physiology to benefit the herbivore. Previous studies could not determine whether insect galls are induced by mechanical or chemical stimuli because feeding and oviposition both occurred at the site of gall formation. We report that the mouthparts of a spruce‐galling insect, Adelges cooleyi, were inserted in stem phloem cells far from induced galls, that tissues between mouthparts and galls appeared normal, and that the ability to initiate galls was inversely correlated with distance from buds (potential gall sites). Thus the effects of chemical stimuli were unambiguously separated from any mechanical influence of probing stylets or ovipositors. Our results strongly suggest that galls were induced by a chemical stimulus transported to buds via vascular tissue and that its efficacy was dose‐dependent.

Feeding Biology and Nutritional Physiology of Psylloidea(Insecta:Hemiptera):Implications in Host-Plant Relations

“…This behaviour, however, appears similar to that of the European and North American Adelgidae (Aphidoidea) infesting different species of Picea (Pinaceae) [36][37][38] . Leaf tissues attacked by free-living Aphalaridae (e.g.…”

Gall induction by hemipteroid insects

“…The feeding effect of many neonate nymphs induces the modification of nearby vegetative buds into galls in about 30 d. Stimulation of gall development at a site farther away, viz., the vegetative axillary bud, is implicated by the translocation of a 'stimulus' over a distance of 10Á15 cm. Such a behavior is unusual among the gall-inducing psylloids (Burckhardt 2005), but is analogous to the behavior of Adelges cooleyi (Adelgidae) that induces galls on the vegetative buds of the hybrid interior spruce (Picea glauca)P. engelmannii) in North America, where a dose-dependent chemical stimulus is transported over long distances from the point where the gall-founding female settled (Sopow et al 2003). In spite of an apparent similarity, in the bud galls of M. indica, the first-instar nymphs of A. cistellata are the purported gall inducers, whereas in the bud galls of Picea glauca )P. engelmannii, adult females of A. cooleyi induce galls.…”

Arthropod-induced neoplastic formations on trees change photosynthetic pigment levels and oxidative enzyme activities

“…There is no biochemical or molecular evidence for any changes of endogenous signals in host plant tissues under the effect of gall formation. However, some directions could be found in the data that hypersensitive response of host plant might be involved (Fernandes 1998) or that systemic transfer of a chemical signal via vascular tissue is necessary for induction of gall formation (Sopow et al 2003). As for insect-derived local signals acting in plant tissues, indole-3-acetic acid and cytokinins recently have been considered (Mapes & Davies 2001a,b).…”