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Larval habitat availability, Typha phytotelmata use and the relation of environmental factors to annual dynamics of the mosquito Wyeomyia leucostigma Lutz, 1904 (larvae and females) were studied in Costanera Sur Ecological Reserve at Buenos Aires, Argentina. Bimonthly, 1520 plants were examined, detecting W. leucostigma in 80.8% of surveys. Larval habitat availability was associated with temperature, but not with rainfall. In addition, the high temperature was associated with greater biting rate. Dynamics of host-seeking were recorded over 10 months of the year and were associated with temperature as well. Furthermore, an accidental fire led to an increase of W. leucostigma abundance likely based on an increase of the Thypha marshes productivity that occurred after the fire. [ABSTRACT FROM AUTHOR]

The adverse effect of pesticides on non-target organisms and the environment is an issue of great social concern. Currently, there are a variety of availably insecticides, which are claimed to be safer for beneficial organisms than broad-spectrum insecticides. We conducted a field experiment to compare the effect of applications of methoxyfenozide (an insect growth regulator) and cypermethrin (a conventional insecticide) on the arthropod community in a commercial willow plantation. We used a one-way Anova design with insecticide as the treatment factor, each individual tree as the experimental unit, and the number of dead arthropods collected per sampling unit as the response variable. Results showed that the number of dead arthropods collected 72 h after treatment with methoxyfenozide (1274 individuals) was 66% lower than that collected underneath cypermethrin-treated trees (3408 individuals). The only groups not recorded from boxes places underneath methoxyfenozide-treated trees, but yes underneath cypermethrin-treated trees, were Dyctioptera, Pseudoscorpionida and Isopoda. Methoxyfenozide was lethal to a lower number of families of dipterans, coleopterans and hymenopterans than the cypermethrin during the first 72 h after treatment. The number of taxonomic groups and abundance of dead predators, herbivores and parasitoids was also lower in methoxyfenozide than in cypermethrin-treated trees. Our results obtained from a field experiment suggest that methoxyfenozide provides a less toxic alternative for control of pests in willow plantations due to a reduced effect on non-target organisms. [ABSTRACT FROM AUTHOR]

Nematus oligospilus Förster (Hymenoptera: Tenthredinidae) is a willow sawfly native to the Northern Hemisphere which became a serious defoliator in willow plantations (Salix spp.) of the Southern Hemisphere after being introduced in the early 1980's. Studies on host preferences provide useful information for the development of pest management strategies where the wi How sawfly may produce tree damage and economic loss. Feeding preferences of N. oligospilus larvae were evaluated in laboratory trials by simultaneously offering leaves from four willow tree clones commonly used in commercial plantations in Argentina (Salix babylonica var sacramenta Hortus, Salix nigra Marsch., S. babylonica L x Salix alba L. 131- 27 and Salix matsudana Koidz. x 5. alba L. 13-44). Larvae of N. oligospilus fed on leaves from the four clones. However, insects consumed a significantly higher proportion of 5. babylonica var sacramenta leaves than of leaves from the other clones. Results indicate that all clones used in the trials were palatable to the insect, and that 5. babylonica var sacramenta is the preferred host for larval herbivory. [ABSTRACT FROM AUTHOR]