This chapter builds on the household model presented in Chapter 5 [Missing markets, migration and crop biodiversity in the milpa system of Mexico: a household-farm model, by van Dusen, M. E., pp. 63-77] by exploring the role of social institutions in household access to planting material and use of crop biodiversity. Two types of institutions are analysed: (i) local community groups to which a household may belong and (ii) sources of planting material and agricultural information. Findings from a household survey implemented in two districts of Samarqand, Uzbekistan, provide a description of the diversity of fruits and nut trees, as well as the nature of systems for planting material. Econometric analysis reveals a linkage between participation in community groups and the levels of fruit and nut tree diversity managed by households. No relationship is found between the type of institution used to obtain genetic material and the level of diversity in orchards. Household participation in community groups influences the type of institution used for access to genetic material, however.
Aldrin dust (3 cwt. of I$ yoper acre) or D D T dust (z cwt. of 5 yo per acre) was applied to small plots replicated four times and four plots were untreated. All plots were kept fallow for one year. Soil samples were taken at 2 to 3-monthly intervals and the fauna extracted by a flotation method. T h e insecticides did not affect Lumbricidae, Enchytraeidae or Nematoda. Nearly IOO species of arthropods were found, and the greatest effects were
S U M M A R YStudies of pheromone traps for Cydia pomonella, Archips podana and Adoxophyes orana (Lepidoptera: Tortricidae) were made in United Kingdom apple orchards from 1974 to 1976. Compared with light traps, they proved easier to operate and, with the exception of those set for Adoxophyes orana, were more effective monitors. There was considerable site-to-site variation in the pattern of weekly catches, and in total catches for each season, such variability often masking inter-regional differences. The data proved useful for deciding if and when sprays should be applied in individual orchards, and were also used as a basis for district spray warnings. Thresholds below which treatment was generally unnecessary were five moths/trap/ wk for C. pomonella and 20 moths/trap/wk for Archips podana, but results for Adoxophyes orunu were inconclusive. Fruit damage in monitored orchards sprayed as advised was generally low.
Karyotypes of six endemic New Guinea Rattus species are described. They fall into two distinct types. The R. leucopus group, which is a compact group morphologically, have very similar karyotypes of 32 or 34 chromosomes and are distinct from the Australian Rattus. The karyotypes of the second type, the R. sordidus group, are related to Australian members of the same group. What has previously been regarded as a single species of the sordidus group, R. sordidus gestroi, is shown to consist of two distinct populations with different karyotypes and skull parameters; we consider that they should be regarded as two species.
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