The Abundance Parasitoid Populations of Neochrysocharis formosa and Neochrysocharis okazakii (Hymenoptera: Eulophidae) on Liriomyza spp. (Diptera: Agromyzidae) Associated with Vegetable Crop in Bali

The research objective was to determine the population abundance and the level of parasitation of parasitoid of Neochrysocharis formosa and Neochrysocharis okazakii against Liriomyza spp on some vegetable crops in Bali (Indonesia) from March 2014 to December 2014. The method used is a survey method; the sampling of Liriomyza spp infected plants was conducted by purposive sampling on the low, medium and high land in Bali.The results showed that the population abundance of N.formosa on planting vegetables in Bali with the highest population respectively in the low, medium and high lands at 642, 409 and 162 populations. N.okazakii in the low, medium and high lands is 243, 99 and 10 populations. N.formosa parasitation highest level was found in the low, medium and highlands respectively on tomatoes, chicories, tomatoes, while N.okazakii on tomato plants. Both parasitoids associated with L.sativae in the lowlands, medium and highlands, with L.huidobrensis only in the medium and highlands. Keywords: Abundance population, N.formosa, N.okazakii, Liriomyza spp., vegetable crop

Latent variables in discrete choice experiments

This paper describes and applies a general approach for incorporating factors with structural equations into models for discrete choice. The approach gives form to the covariance matrix in random coefficient models. The factors act directly on the random coefficients as unobserved attributes. The structural equations allow the factors to act on each other building structures that can represent a variety of concepts such as global heterogeneity and segmentation. The practical outcomes include parsimonious and identified models with rich covariances and better fit. Of greater interest is the ability to specify models that represent and test theory on the relationships between the taste heterogeneities for covariates and in particular between the attributes within a discrete choice experiment. The paper describes the general model and then applies it to a discrete choice experiment with seven attributes. Four competing specifications are evaluated, which demonstrates the ability of the model to be identified and parsimonious. The four specifications also demonstrate how competing a priori knowledge of the structure of the attributes used in the experiment can be empirically tested and evaluated. The outcomes include new behavioral insights and knowledge about choice and choice processes for the subject area of discrete choice experiments