Effects of two potential pest management components, intercropping and yellow sticky plastic sheet traps in two differentially resistant potato cultivars for the management of myzus persicae (Sulzer)

Polyculture is traditionally a low-input agricultural system and is important in many developing countries. Polycultures of interplanted crops often support fewer pests at lower densities than monoculture and tend to increase number of natural enemies. Also Yellow Sticky Plastic Sheet Traps have proved useful for trapping aphids. A field study was conducted to study the effectiveness of these potential pest management techniques along with the partially resistant (Cardinal) and susceptible (Desiree) potato cultivars, by using their different combinations for the management of Myzus persicae (Sulzer). Berseem, Trifolium alexandrinum (L.) (family: Leguminosae) was used for intercropping with potatoes. The different combinations (treatments) used in this study were: 1) Cardinal-berseem mixed cropping+yellow sticky plastic sheet traps 2) Cardinal-berseem mixed cropping 3) Cardinal+yellow sticky plastic sheet traps 4) Cardinal separately+berseem (as land area equivalents in relation to the mixed cropping treatments) 5) Cardinal (sole crop). Treatments 6-10 were the same treatments, but with Desiree as the potato cultivar. All these treatments were used to evaluate their effects as management techniques for M. persicae, their percent parasitism, percent emergence rate of the parasitoid, Aphidius matricariae Haliday and yield of Cardinal and Desiree. Mixed cropping of Cardinal and berseem together with the yellow sticky plastic sheet traps reduced aphids by over 90% compared with numbers on the sole Cardinal crop. This combination proved in this experiment the most effective for reducing the aphid populations as compared with all other treatments. Maximum percent parasitism i.e. 6.97 and 6.94% (almost double that in the other treatments) was recorded in the potato berseem mixed cropping, with and without traps respectively. In the same two treatments, yield was increased significantly as compared with all other treatments. However no significant effects of any of the variable was evident on the percent emergence of A. matricariae.

How does employment density influence individuals’ wages? : A micro data approach.

We estimate the effect of employment density on wages in Sweden in a large geocoded data set on individuals and workplaces. Employment density is measured in four circular zones around each individual’s place of living. The data contains a rich set of control variables that we use in an instrumental variables framework. Results show a relatively strong but rather local positive effect of employment density on wages. Beyond 5 kilometers the effect becomes negative. This might indicate that the effect of agglomeration economies falls faster with distance than the effects of congestion.

Informal wages in an economy with active labor courts

In most developing countries, job regulations and the justice branch interfere on several aspects of labor contracts. Inspired by this fact, we build a model that explores the role of labor courts in the determination of the di¤erence between formal and informal wages. We show that the presence of active labor courts in an environment where labor relations are subject to asymmetries of information reproduces features documented by the empirical literature. The main implications of our model are tested using Brazilian data.

The distribution of male wages in Brazil

This paper examines the evolution of wage inequality in Brazil in the 1980s and 1990s . It tries to investigate the role played by changing economic returns to education and to experience over this period together with the evolution of within-group inequality. It applies a quantile regression approach on grouped data to the Brazilian case. Results using repeated cross-sections of a Brazilian annual household survey indicate that : i) Male wage dispersion remained basically constant overall in the 1980's and 1990' s but has increased substantially within education and age groups. ii) Returns to experience increased significantly over this period, with the rise concentrated on the iliterate/primary school group iii) Returns to college education have risen over time, whereas return to intermediate and high-school education have fallen iv) The apparent rise in within-group inequality seems to be the result of a fall in real wages, since the difference in wage leveIs has dec1ined substantially over the period, especially within the high-educated sample. v) Returns to experience rise with education. vi) Returns to education rise over the life-cycle. vii) Wage inequality increases over the life-cycle. The next step i~ this research will try to conciliate all these stylised facts.

Does money in schools matter? evaluating the effects of FUNDEF on wages and test scores in Brazil

In this paper we investigate the effects of the 1998 reform in the funding of fundamental education in Brazil (FUNDEF) on the relative wages of public school teachers and on the relative proficiency of public school pupils. The evidence suggests that, on average, FUNDEF raised the public school teachers’ relative wages and improved the relative proficiency of the public school students. Some indirect evidence was presented that showed that the effect of FUNDEF on proficiency seems to be related to its effect on wages and on school characteristics. The effect on proficiency seems to be concentrated in the municipal schools in the Northeast of the country.

Are Central American export specialization patterns "sticky"?

Includes bibliography

Wages and employment in international recessions: recent Latin American experience

Includes bibliography

Education and wages of vocational training graduates

[EN] This paper attempts to explain individual variation in wages by estimating different wage equations. The study has two goals: first, to analyze the effect of years of schooling on the wages of vocational training graduates using a more precise measure for schooling than that commonly used in wage equations; and second, to analyze the effect on these wages of the match or mismatch between the knowledge and the skills acquired in the schooling and the needs of the job. The analysis shows that knowledge and skills acquired through vocational training (over-/under- education and over-/under- skilling), have a statistically significant influence on wages.