Sucking Herbivores Research Articles

Variation in Growth, Chemical Defense, and Herbivore Resistance in Scots Pine Provenances

Variation in the growth, chemical defense, and susceptibility to monophagous and polyphagous sucking herbivores was assessed for four Scots pine (Pinus sylvestris) provenances in Petri dish and pot experiments. Seed provenances, Muonio (MU), Suomussalmi (SU), Korpilahti (KO), and Saaremaa (SA) represented a 1200-km N–S gradient. Scots pines from SU were least preferred as a host plant by pine-feeding aphids Schizolachnus pineti Fabr. and Eulachnus agilis, and in pot experiments, pines from SA were most preferred. S. pineti also produced the fewest nymphs on pines from SU. Polyphagous Lygus rugulipennis laid significantly fewer eggs on pines from MU provenance, which were smaller than seedlings from other provenances. The total and some individual terpene concentrations increased, while the total resin acid concentration decreased, towards the north. The absolute concentrations of total or individual terpenes and resin acids in the needles of unfavored SU plants did not differ significantly from the other provenances. Only the proportional quantity of dehydroabietic acid was higher in SU plants than in KO plants, and it correlated, together with sandaracopimaric acid, negatively with the number of S. pineti nymphs in the reproduction experiment. Conversely, absolute concentrations of some terpenes correlated negatively and some resin acids positively with the number of S. pineti nymphs. The length and weight of shoots decreased towards the north, adequately explaining the number of Lygus eggs and the final numbers of both aphids. The results suggest that seedling size is a better estimator of susceptibility of pine seedlings to both specialist and generalist sucking insects than relative or absolute concentrations of monoterpenes and resin acids.

Herbivory by Chewing and Sucking Insects on Tabebuia ochracea

Our study addresses the influence of Tabebuia ochracea leaf variation on insect herbivores. We studied the roles of leaf size, age, and hairyness in the feeding choices of chewing and sucking herbivores. The T. ochracea studied belonged to a single clone, thus decreasing the potential influences of host plant genetic and chemical variation on herbivore choice. Young and mature leaves showed the same amount of damage from chewing herbivores in the field. Homopterans (Rhabdotalebra spp.) and hemipterans (Tingis tecomae) occurred primarily on large leaves. The leaf area consumed by grasshoppers in a laboratory experiment was higher on young leaves than on mature leaves. Nevertheless, there was no difference in the choice by Rhabdotalebra spp. and T. tecomae for young vs mature leaves of T. ochracea. Mature, large leaves were chosen over mature, small leaves by Rhabdotalebra spp. and T. tecomae. In a laboratory experiment, T. tecomae did not choose between leaf circles of same size taken from large or small leaves, indicating that the most relevant factor in its food choice was leaf size. Nevertheless, Rhabdotalebra spp. significantly chose leaf circles taken from large leaves, indicating that leaf trichome density was an important component in its food choice. The differential distribution of small and large leaves was important in the food selection by T. tecomae; whereas, trichome density was a relevant factor in food selection by Rhabdotalebra spp.