Preface. 1. Introduction. 2. Feeding Behaviour and Food Quality. 3. Host Specificity and Speciation. 4. Size. 5. Resource Tracking: Mechanism - Cyclical Parthenogenesis. 6. Resource Tracking: Mechanism - Polyphenism. 7. Resource Tracking in Time. 8. Resource Tracking in Space. 9. Population Dynamics. 10. Community Structure and Species Diversity. 11. Epilogue. References. Index.

Aphid Ecology An optimization approach

The role of natural enemies on the population dynamics of the rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae) in organic apple orchards in south-eastern France

Episyrphus balteatus (DeGeer) (Diptera: Syrphidae), Adalia bipunctata (L.) (Coleoptera: Coccinellidae) and Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) are the three most abundant natural enemies of Dysaphis plantaginea Passerini (Homoptera: Aphididae) in Asturian (NW Spain) apple orchards. They attack this aphid in sequence: E. balteatus arrived first, followed by A. bipunctata and then by A. aphidimyza. The cecidomyiids arrived too late to have a regulating effect. The syrphids laid an average of 2.3 ± 1.7 eggs per aphid colony and the coccinellids 18.4 ± 9.9 regardless of the degree of the infestation rates of the apple shoots. This value corresponds to the size of an egg batch laid by one female. Therefore, these aphid predators did not respond numerically to the abundance of the pest. The results of this study indicate that natural populations of syrphids and ladybird beetles are unable to control D. plantaginea, and therefore a more complex strategy than waiting for natural enemies is required.

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Colonization of apple orchards by predators of Dysaphis plantaginea : sequential arrival, response to prey abundance and consequences for biological control

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

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

Effect of codling moth exclusion nets on the rosy apple aphid, Dysaphis plantaginea, and its control by natural enemies

SUMMARY
Dysaphis devecta causes the leaves of its host plant to roll laterally whereas D. plantaginea causes them to roll longitudinally. Both species of aphid are phloem feeders. D. devecta prefers to feed on the smaller veins in the lamina whereas D.plantaginea chooses the midrib. However, groups of D. devecta or D. plantaginea confined to the stem of an apple seedling induced young leaves several centimetres away to develop leaf rolls characteristic of each species. A single larva of D. devecta or D. plantaginea can induce a leaf-roll or a stem-bend on an apple seedling within 24 h. It is suggested that characteristic abnormalities in leaves attacked by D. devecta and D. plantaginea are caused by specific substances in the saliva of each aphid.

J. M. S. Forrest

Papers

The induction of leaf‐roll galls by the apple aphids Dysaphis devecta and D. plantaginea