Volatile Profiling of Fifteen Willow Species and Hybrids and Their Responses to Giant Willow Aphid Infestation

The giant willow aphid (Tuberolachnus salignus) is a large stem-feeding insect which forms dense colonies on infested plants. Since T. salignus is a new invasive species in New Zealand, we have a poor understanding of the plant chemical responses to aphid infestation. This study aimed to characterize the volatile organic compounds (VOCs) emissions of fifteen different willow species and hybrids growing in New Zealand, and to evaluate changes in response to T. salignus attack in a field trial. Volatiles were collected using a headspace sampling technique and analysed using gas chromatography-mass spectrometry (GC-MS). We found high variability in the volatile profiles of different species and hybrids, with (Z)-3-hexenyl acetate and (E)-β-ocimene being the only common components to all blends. Taxonomically related plants showed an overlapping pattern of VOC emission, and there seemed to be a clear separation between shrub and tree willows. Responses to aphid infestation were variable, with only four species/hybrids showing changes in their total VOC emission, or that of at least one class of VOCs. A weak positive correlation between aphid population estimates and VOC emissions suggests that responses are species-specific and not infestation-dependent. These results reveal useful information about the interaction between T. salignus and its potential host plants for biological control and pest management purposes.

Honeydew Deposition by the Giant Willow Aphid (Tuberolachnus salignus) Affects Soil Biota and Soil Biochemical Properties

Infestation of willow plants by the giant willow aphid Tuberolachnus salignus (Hemiptera: Aphididae) is associated with copious deposition of sugar-rich honeydew under the plant canopy. We explored the effect of aphid honeydew on the soil biota and biochemical indicators in a two-year field trial. Soil samples from under aphid-infested and control willow trees, as well as samples from black sooty mould spots under the aphid-infested willows were compared; soil samples before aphid inoculation were used as a baseline. The honeydew deposition had a positive effect on the total soil carbon (C), but not on the total soil nitrogen content or soil pH. Microbial biomass C, basal respiration, number of yeast colony forming units, and the geometric mean of activities for six enzymes were significantly higher in honeydew-affected soils than in the control treatment on both years. The honeydew deposition also increased soil meso-fauna abundance, especially in the black sooty mould spots. The soil biochemical properties, which differed before and after aphid infestation, showed considerable overlap between the first and second year post-infestation. The results highlight the cascading effects of T. salignus on soil biological activity and the importance of using a multitrophic approach to explore similar scenarios.

AFIDOS (HOMOPTERA:APHIDAE) DEL VALLE DE CAÑETE (LIMA - PERU)

Se han identificado las siguientes especies procedentes del valle de cañete : Aphis citicola, A.craccivora, A. fabae, A.gossypii, Brevicoryne,brassicae, Lypaphis erysimi Macrosiphum euphorbiae, M. rosae, Myzus persicae, Riopalosiphum maidis, R. padi, toxoptera aurantii, T. citricidus y tuberolachnus salignus Todos los áfidos identificados representan especies de importancia económica, excepto el último.