An insight into some relevant aspects concerning eriophyoid mites inhabiting forests, ornamental trees and shrubs.

Worldwide a great variety of eriophyoid mites inhabit forest canopy trees and ornamental plants that are used in city parks, squares and boulevards. An analysis of the relevant bibliography portrays only a fragmentary knowledge and the majority of our information concerns the temperate zone. Three case studies are presented as examples of different approaches to solve problems connected with eriophyoid mites of forest and ornamental trees. The first example deals with eriophyoids of a temperate zone forest in a natural environment, focusing on conifers which represent the largest component. The second case study documents a possible approach to obtain greater knowledge and control of the bud mite species, Trisetacus juniperinus (Nalepa) on Cupressaceae. This is a harmless species in the natural environment which becomes a serious pest in nurseries and young stands of Cupressus sempervirens in the Mediterranean region. The final case study reports on long-term studies carried out in Poland on injurious eriophyoid species that are found in nurseries, city greenery and parks. This paper also discusses future perspectives for research on eriophyoid mites living on forest and ornamental plants.

Tomato transgenic lines and Tetranychus urticae: changes in plant suitability and susceptibility.

A critical aspect dealing with the use of transgenic plants is the global evaluation of their environmental impact. The polyphagous mite Tetranychus urticae can be considered a suitable species to investigate unpredictable and undesirable effects on phytophagous arthropods. Three tomato near isogenic lines, that is, the cv. Riogrande (RIG), the transgenic lines RC332 (containing the Gox gene and showing high glucose oxidase activity), and MS498 (containing the KTI3 gene and exhibiting a high trypsin inhibition) were used in laboratory and greenhouse trials. Trichomes and contents of C and N of the leaves, differences in development and oviposition of T. urticae and damage caused were evaluated for each line. The laboratory trials evidenced that (1) the intrinsic rate of increase of two strains of T. urticae (T from tomato, B from bindweed), reared on the lower surface of tomato leaflets, was significantly lower in RIG than in transgenic lines and doubling time ranged between 6.9 and 11.6 days in the first and between 3.9 and 5.3 days in the latter; (2) the glandular four-lobed trichomes were always higher in RIG than in other genotypes; (3) the N leaf content was from 1.3 to 1.9 fold lower and the C/N ratio from 1.3 to 1.9 fold higher in RIG than in other lines. The greenhouse experiment, that lasted over a month and was performed by inducing an initially equal infestation of strain T, evidenced: (1) no significant difference between plant lines in the final mite infestation (motile stages per plant), nevertheless an almost double number of spider mites was counted in RC332; (2) a significantly higher percentage of damaged leaves and a significant higher average damage index on RC332 than on RIG (79% and 2.3 in the former, and 62% and 2.1 in the latter, respectively), even if in both transgenics a higher level of the most severe damages and a shorter time to approach them were observed; (4) a comparable number of mites causing the same damage level in all genotypes and a strong linear relation between the first four levels of damage and mite infestation. Although in the laboratory studies both transgenic lines enhanced the T. urticae population increase, the glasshouse studies were not as conclusive and they only suggest the possibility of any real difference between the transgenic and non-transgenic genotypes.