Phenolic compounds in 46 Spanish cider apple varieties were determined by RP-HPLC with direct injection. Several pattern recognition procedures, including principal component analysis (PCA), linear discriminant analysis (LDA), and partial least squares (PLS-1), were applied to the data in an attempt to classify the samples into bitter and nonbitter categories. Reliable decision rules were obtained by both LDA and PLS-1. LDA achieved 91.3 and 85.7% correct classification respectively, for internal and external evaluation of the model.
Abstract. Episyrphus balteatus (DeGeer) (Diptera: Syrphidae), Adalia bipunctata (L.) (Coleoptera: Coccinellidae) and Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) are the three most abundant natural enemies of Dysaphis plantaginea Passerini (Homoptera: Aphididae) in Asturian (NW Spain) apple orchards. They attack this aphid in sequence: E. balteatus arrived first, followed by A. bipunctata and then by A. aphidimyza. The cecidomyiids arrived too late to have a regulating effect. The syrphids laid an average of 2.3 ± 1.7 eggs per aphid colony and the coccinellids 18.4 ± 9.9 regardless of the degree of the infestation rates of the apple shoots. This value corresponds to the size of an egg batch laid by one female. Therefore, these aphid predators did not respond numerically to the abundance of the pest. The results of this study indicate that natural populations of syrphids and ladybird beetles are unable to control D. plantaginea, and therefore a more complex strategy than waiting for natural enemies is required.
A field experiment was conducted in a cider-apple orchard to evaluate the effect of six groundcover management systems (pine-bark, plastic and straw mulches, tillage, herbicide and natural soil) on the occurrence of ground beetles (Coleoptera: Carabidae).Eight species of carabids were collected in pitfall traps. The three most common beetles, Steropus gallega Fairmaire (65.8%), Pseudophonus rufipes (DeGeer) (18.2%) and Poecilus cupreus L. (14.6%), represented more than 98% of the total catches. The specific dominance depended on the sampling date. The soil management treatment significantly affected the following parameters.(1) The overall carabid catch: the plastic mulch (5.6% of the total catches) negatively affected total carabid collection, which was higher in the tilled (24.3%) and herbicide-treated (21.4%) plots, although not significantly different from the natural soil (16.5%), straw mulch (16.3%) and pine-bark mulch (15.9%) treatments. (2) The specific preferences of the three most common carabids: the plastic cover adversely affected the catches of S. gallega whilst P. rufipes was collected in greater numbers in tilled areas and P. cupreus in the herbicide treatments. (3) The structure of the carabid community: based on species richness, diversity and evenness indices, herbicide and tillage provided the most diverse carabid community and the straw mulch the poorest. It was concluded that groundcover management in apple orchards may affect the activity density of epigeic predators which may contribute to the natural control of pests.
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