María T. Defagó

Effects of Melia azedarach on Triatoma infestans

Extracts from fruits and leaves of Melia azedarach were tested for repellent and insecticidal properties against eggs and nymphs of Triatoma infestans, the vector of Chagas disease. Unripe fruit extract was highly repellent for first and fourth instar nymphs. Ripe fruit had a weaker effect while leaves were ineffective. No effects on egg hatching, nymph survival or development time were detected, but first instar nymphs reared in contact with extract-treated refuges were significantly smaller than controls after moulting.

Chapter 5 Role of Melia azedarach L. (Meliaceae) for the control of insects and acari: present status and future prospects

Publisher Summary Various families of plants possess anti-insect compounds. From the Meliaceae family, insecticide molecules have been isolated, the limonoid azadirachtin obtained from Azadirachta indica or Melia azadirachta (neem) being the most potent and studied. Another tree belonging to the Meliaceae family, far less studied than the previously mentioned, is Melia azedarach . This chapter presents information about the active principles isolated by various investigators from M. azedarach together with their respective bioactivities. Moreover, the chapter describes the effects on feeding, growth, larval and pupal development, fecundity, fertility, toxic effects, as well as alterations in the insect morphology of different extracts.

Something is lost and something is gained: loss and replacement of species and functional groups in ant communities at fragmented forests

ContextSmall fragments of natural habitats with an increased proportion of edges are common landscape traits following agricultural expansion. Consequences of habitat fragmentation are widely documented. However, functional and mechanistic approaches are still needed in order to understand these changes.ObjectivesWe studied habitat loss and edge effects on ant communities, addressing changes in species and functional group diversity, and the relative importance of β-diversity components.MethodsIn an endangered Neotropical forest, we sampled ants in edge and interior habitats using pitfall traps, during three summers (28 sites). We calculated taxonomic, phylogenetic and functional diversity and partitioned taxonomic and functional β-diversity into replacement and loss/gain components.ResultsWe found more species and functional groups at edge than interior habitats, and four species were edge indicators. Habitat loss negatively affected total abundance and that of particular functional groups (fungus-growers and cryptic species) but had a positive effect on taxonomic, phylogenetic and functional diversity as well as abundance of opportunists and predators. Species and functional group replacement drove β-diversity, being linked to habitat loss. However, interactions between habitat loss and edges explained the loss/gain of taxonomic and functional composition.ConclusionsFragmentation led to enriched ant communities at edges, possibly resulting from a higher influx of matrix species as edges become pervasive. This highlights the need to assess the spillover between habitats to understand its influence. Moreover, species replacement and the decrease of functional groups due to habitat loss could have an impact on ecosystem processes in which ants play an important role.

Can the extract of Aristolochia argentina Griseb affect the foraging decisions of the leaf cutting ant Acromyrmex lundi (Guérin)? Preliminary assays

ABSTRACT The aim of this study was to evaluate whether foraging decisions of Acromyrmex lundi in the field are affected by the extract of Aristolochia argentina. A free choice test was performed using Rosa x hybrida leaves treated with the extract and control with acetone. Two leaves (treated and control) were presented on either side of a foraging trail. The percentage of removed material was recorded for 90 minutes of observation on two consecutive days. Dry weight and repellency index were calculated. Ant activity, the percentage of carried leaves and weight data were analyzed using a “t”-test for paired data, and a General Linear Mixed Model test was used to evaluate the different variables and their interactions. A. argentina extract (1%) did not affect the foraging activity of A. lundi, whereas the 5% dose caused significant differences in foraging activity as well as between the factors and the interactions. A repellency index of above 95% was obtained at the 5% dose. The extract of A. argentina could be considered for future management of this insect.